Datasets:

vishnun0027

/

eli5_dataset

like 0

{ "a_id": [ "gikxpsv", "gikyuk3", "gikxzop", "gikx7m0", "gikxkuw", "gikz1th" ], "text": [ "It's a form of energy that's very easy to transport (all you need is some metal wires), and easy to convert to light and to motion. Gasoline, diesel, propane gas, and other fuels can produce light and motion, but are more difficult to transport. However, we do use them a lot.", "With enough futzing you can make any source of energy do anything really. Electricity is useful because it works on a very small scale and a very large scale, it pretty easy to obtain and transport. It's also nice because it is easier to get electricity to do just what you want without generating a bunch of unwanted effects like heat or additional kinetic energy.", "Check out chemistry. Every element that EVERYTHING is made of has an associated electrical charge. Since everything is basically electric, you can manipulate everything with electricity by utilizing the different associated properties.", "Electricity can be used as a signal with 2 states, on and off, 1 and 0, which can be translated into code (binary) for more complex things or simply on off for basic things like a light.", "Electricity itself can only really do two things - move electrons through a medium, and generate a magnetic field. It's kind of like a river. We can swim in it, we can sail on it, we can divert it to grow food, we can put water-wheel in it to perform work, but we don't say that the water is doing everything.", "Electricity is a source of energy. Most sources of energy can also do 'everything'. Chemistry is what drives the brain. Mechanical computers exist and cars can be exclusively mechanical devices. You could replicate computers and machines in exclusively hydraulics, too. However, electricity is convenient in that it's easy to transport compared to high-pressure hydraulic fluid or chemicals or a driveshaft. It also doesn't require any fluids or anything that can make a mess or add difficulty. It also doesn't lose efficiency at small scales and can easily have circuits made on the atomic scale." ], "score": [ 8, 6, 5, 5, 5, 5 ], "text_urls": [ [], [], [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gin8i3j" ], "text": [ "In the development of embedded software like this, the designer will use a *development board* which breaks out all the chip's pins and peripherals to write and test the microcontroller software, once it does everything it needs to do and the custom circuit board in the toy is designed, the microcontroller program is loaded onto the chip either via a debug port on the board (uncommon) or by a separate machine before it's even put onto the board." ], "score": [ 6 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gin7jug", "ginuby5", "ginh6hp" ], "text": [ "It gets sucked into a septic tank aboard the plane. It's loud because it uses a very high differential pressure to do that. It allows you to remove all the waste whilst using very little water", "It gets sucked into a septic tank. The tank is then emptied by a ground service vehicle once the plane lands. The interesting part is that on the ground and below an altitude of about 14000ft (varies by plane type), the noise comes from a vacuum generator that sucks the waste into the tank. The vacuum generator is like a very powerful vacuum cleaner engine, so it makes a lot of noise. Above that altitude, the differential pressure between the cabin (where you can breathe) and the unpressurized tank (outside pressure) is so large that the waste is sucked down by just opening the seal at the bottom of the toilet. The noise here comes from the air moving rapidly through a tube that gets tighter and tighter. An unrelated fun fact is that the oxygen percentage is the same at high altitudes as on the ground. It's the lack of pressure at high altitudes that make our lungs unable to use that oxygen. That's why the cabin on an aircraft is pressurized with air rather than pure oxygen. When people say there's less oxygen at higher altitudes, they're actually wrong. Source: I work as an airline pilot.", "It gets sucked into special container and when you land its taken out by trucks similar to these that take waste out of latrines" ], "score": [ 87, 84, 7 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giot65m", "giotp9x" ], "text": [ "Your shower has two water supplies, hot and cold. When you take a hot shower, you're actually usually using a mixture of both. That allows you to have the temperature of water that you want. Your toilet only has one water hookup; cold. When you flush it, a bunch of cold water rushes into it to refill the tank. That makes the water pressure nearby drop. So your shower which was lovingly adjusted by you to be just the right temperature suddenly can't get enough cold water. But it still has plenty of hot water! The result is that you suddenly find yourself in a shower that's much too hot for your liking.", "Adding to what other said. Newer single handle shower valves have a temperature mixing valve that helps avoid scalding. I grew up in an old house with old valves, and lived through a lot of sudden scalds." ], "score": [ 9, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giovsn5" ], "text": [ "Oil will break down over time due to high temperatures in the engine (known as thermal breakdown). Because of this, the oil isn’t capable of providing the necessary lubrication for metal parts after an extended period of use. Without lubrication, the moving joints in the engine will start rubbing against each other and cause premature wear. Oil also has a limited capacity on how much particulates it can hold. By not changing the oil, particles already in the oil will begin to settle and cause corrosion. One of the biggest dangers of not changing your oil is sludge buildup. Sludge occurs when old oil begins to gel or solidify in an engine. When sludge begins to build up, oil isn’t able to flow freely through the engine and can cause oil starvation to crankshafts, bearings, camshafts, and other valve train components not be lubricated. In time, this can cause major damage to the engine and, in the worst situations, require an engine replacement or rebuild. If the oil isn’t changed, your vehicle’s engine will start to have a lot of problems. The most common issue is that the parts in your engine will become too hot. This can cause the engine to run less efficiently, and as time goes on, it can cause the engine components to warp and wear out. The lack of lubrication between these parts will also contribute to these problems. Eventually, if the oil is not changed, the entire engine will shut down and have to be replaced. This repair can cost thousands of dollars" ], "score": [ 8 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gipx0nh", "gipn07j" ], "text": [ "Older cars used drum brakes on all 4 wheels. These were reliable, simple to manufacture, and provided a lot of braking force for a given size and weight. They are also resistant to warping of the rotor drum. Because the brake shoes and cylinder are enclosed in the drum, wear due to road grit and corrosion is less of an issue, giving longer life of the pads. For this reason large trucks still often use this design because disc brakes wouldn't offer the same performance, would be excessively large and would require more costly maintainence. The downsides of these brakes are twofold. The first is the drum and pads aren't well ventilated and can't cool down quickly. Friction can therfore cause the drum to get red hot, leading to the second downside. That is, a reduction in friction with the pads for physics reasons that are complex. This is called brake \"fading.\" It can potentially cause an ignorant driver to apply more force to the pedal, accelerating the heating. It can also cause the brake fluid to boil if the cylinder gets hot enough in that situation, causing a loss of brakes and potentially a wheel fire. This is a severe shortcoming and has caused far too many fatalities to mention. Modern cars tend to use disc brakes in the front at least. Car discs brake rotors have ventillation passages in the center and often slots or cross drilled holes providing additional surface area for air to flow through and cool the rotor. This causes them to be more resistant to overheating. However they are by no means immune to this and can still suffer from fading or even fires in extreme cases. (In all cases it's best to downshift the engine to reduce the need for braking on a long downhill stretch.) Modern cars still to this day may use drum brakes in the rear for several reasons. This is because less braking effort is needed in the rear wheel due to the tendency of the car to pitch forward therefore less heat is generated. In any case for the same reason the rear wheels will lockup and skid much sooner than the front, so the rear brakes need to be smaller by necessity. As I mentioned drum brakes generally are less prone to needing maintainance and less prone to vibration problens caused by the rotor warping from heat. They are also much easier and cheaper to manufacture. Another feature of note is the emergency brake is usually actuated with a simple cable and sleeve system like those used on bicycles, independent of the brake lines. This activates the rear brakes mechanically instead of hydraulically, with a simple cam system. This works as a backup system in case there's a loss of brake fluid for some reason. This feature is more difficult to accomplish with rear disc brakes, again, the reasons are complex.", "Modern disc brakes can overheat with hard use, or poor use. When that happens, braking performance goes down. Keep pushing them, and the fluid boils and then they become pretty much worthless." ], "score": [ 7, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giqhdzi", "giqheix" ], "text": [ "As far as the plugs themselves go, those sockets were generally in use before the advent of ground fault circuit interrupters (GFCI), which are the little buttons on outlets that trip in the event of an issue and shut the power off. Since most of Europe uses 220-240V instead of 110-120V, outlets in the bathroom were especially worrisome because there was a higher chance of electric shock with the higher voltage. They opted to instead have lower powered outlets for use near water to help with safety. Most of those outputs are also limited in the amount of current (and therefore total power) they can produce. You can actually use them with many small American electronics, but once you get something that needs more power (like a hair dryer) they won't actually work properly, and it will trip the fuse or damage the transformer in the socket since it isn't rated for the higher current. The frequency of the AC won't change either, so in Europe you would still be getting 110V @ 50Hz , which is weird. Because this standard is still being used, manufacturers of shavers and electric toothbrushes include the plugs necessary to utilize them; it would be silly to make a product that wouldn't work with outlets specifically designed to work with them.", "In the UK, it's in order to prevent you plugging a regular device like a hairdryer into those sockets, since those are a risk in a wet environment like a bathroom." ], "score": [ 6, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gisg70p", "gisggls", "gisg8vz", "gisitxy", "gisk4hi" ], "text": [ "Photosynthesis creates chemical energy (sugars), not electrical energy. You can use the sugars as an energy source, that’s where the energy in oil and natural gas comes from, or biomass heating plants. Then use that to power electrical devices or charge batteries for later power. And you can use the same energy source as photosynthesis (the sun) to directly create electrical energy using solar cells.", "We can. Burn wood, made powered by photosynthesis, run a boiler and generator off it. Or burn oil. A product of ancient photosynthesis. Directly, photosynthesis doesn't produce electrical energy. It produces more energy-rich chemical compounds.", "I think photosynthesis creates sugars. The root question is can sugar power electronic devices. Answer that first then you know a way to slowly make sugar in small amounts.", "To a degree, you can. Like these algae farms make sustainable biofuels: URL_0 Now if you're asking why we can't make photosynthetic batteries out of plants rather than traditional solar panels, that's not a question i can personally ELY5.", "Photosynthesis doesn't create electricity, it creates sugar which provides chemical energy because the mitochondria is the powerhouse of the cell. You'd have to have a way to turn the chemical energy into electrical energy, which isn't efficient enough to make it worthwhile." ], "score": [ 15, 10, 5, 5, 5 ], "text_urls": [ [], [], [], [ "https://www.energy.gov/eere/videos/energy-101-algae-fuel" ], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giubcp0", "giuav13", "giuck6y" ], "text": [ "Cars do use a throttle. That's what the gas pedal is. Planes don't have a transmission because the engine speed is not directly linked to the vehicle speed. A planes engine can be at maximum speed, with the thing barely even moving like at the start of takeoff. The fact the propellers can spin at speeds completely independent of the body's speed gives it this freedom. That said, planes sometimes do modify propeller pitch or other things in addition to engine throttle. Same idea as a transmission, but rather than trying to change the speed in trade off for torque, changes the air being pushed in trade off for torque at the same speed. They don't just have a throttle usually. The same can be said for a boat too, as the speed of the propeller and motor has nothing to do with the boat speed, transmission is not needed. Cars do not have this luxury. The wheels are directly linked to the engine. Speed matches the speed of the engine, with some fixed factor. If the wheels aren't spinning, the engine can't be spinning. If you go twice as fast, the engine needs to spin twice as fast. Even if you're coasting downhill and need zero power from the engine, the engine still needs to match the vehicle speed. A internal combustion engine is really terrible for this. It has a narrow speed range of maximum efficiency, a narrow faster speed of maximum power. Below that, it will stall. Above that, it will destroy itself from spinning to fast and getting to hot. You have about 1000 RPM to 6000 RPM to work with. If the car had no transmission, 1000 RPM could equate 10 km/h and be on the verge of stalling with almost no acceleration. 2000 RPM and 20 km/h would be an ideal cruising. 6000 RPM and 60 km/h would have burn through fuel like crazy, be very loud, and have a tonne of power still. Push the pedal more and it could shoot for 70km/h, it has the power. But it will blow itself in the process. Not a very useful car, limited range and horribly efficiency. Although, it can be done. See a cheap go cart. One gear works fine if fuel economy is not that big of deal and you plan to go one speed the whole time, limited by a governor rather than the engine so you don't blow it. Enter a transmission. A transmission allows you to change the relationship between the engine and the wheels. If the vehicle moves twice as fast, the wheels spin twice as fast, but a different gear ratio can make the engine spin the exact same speed. So from 10lm/h to 120 km/h, the engine is in a good range. The car can also accelerate faster in a lower gear, which is good. You need to accelerate when going slow not so much when already going fast. Shifting down can also give you more torque and power to accelerate or go up a hill, while shifting up works for cruising efficiently. Also, enter a clutch or torque converter. They cover the no speed problem. A clutch uses friction without full interlock to transfer power from a moving engine to stationary wheels. A torque converter in an automatic car is basically one fan blowing on another fan. Some oil rather than air in-between though. This is why you can hold the brake and stop an automatic car without stalling and still having a forward force the brake needs to hold back. But roadworthy cars in no way need a transmission, or a clutch / torque converter. Electric cars don't have them. An electric motor has no issue operating at near zero speed, it can't stall. And it has a wide range of speeds it can operate at with good power, high torque, and high efficiency.", "Answer: both planes and boats are moving a fluid for locomotive power. Cars, on the other hand, are connected to the road, which is solid, and therefore unforgiving when it comes to stopping movement and keeping the motor running. So there's a transmission (mainly a clutch) which can be physically disconnected at idle, whereas fluids can just flow around the prop if the vehicle isn't moving but the prop is.", "Many propeller aircraft effectively *do* change gears. They do this by varying the pitch of their propeller(s)." ], "score": [ 22, 7, 3 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giucjia" ], "text": [ "Depends on the laws where you live. In North America, owning land means you own the surface level. Below a certain depth, someone else usually owns - in the form of mineral rights." ], "score": [ 7 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giv636y", "giv7sfx" ], "text": [ "Fish finders are using active sonars to find fish. They send out a specific sound into the water and then records the echos. This is then displayed on a screen for a trained operator to interpret. Both fish and turtles will return an echo signature and therefore appear on the screen. However the echo does not appear the same. So a trained operator could see the difference between the different signatures. Even if the echo signature might look similar you can determine from the behavior of the different species which one it is.", "Fish finders work with sonar sending a wave out and recording the wave that bounces back. If it hits the seafloor and bounces back it means there are objects between the boat and the seafloor. Now imagine the sea is 100 meters deep. To simplify, lets imagine it takes 10 seconds for the sound wave from the sonar to hit the seafloor and travel back to the boat on the surface. This means the wave travelled for 10 seconds, and knowing the speed at which the wave travels through the medium (lets say a constant of 100 meters in 5 seconds), the fishfinder knows that it travelled 200 meters (100 meters down + 100 meters up) in 10 seconds. If a fish or any other object for that matter is at a depth of 50 meters for example, the sonar will bounce off of the object, instead of the seafloor in that location. In that case, the sonar would return to the receiver of the fishfinder in 5 seconds, and given that we know the speed at which the wave travels, we can deduce that the object is located at 50 meters, meaning the wave travelled a total of 100 meters. This gives us the depth at which the object is. Additionally, the object will reflect the waves in a different pattern depending on the size and shape, which the fishfinder can decode and draw an approximate size on the display for you to see. Given all these parameters, a fishfinder can give you the depth and size of the object. The operater must be trained to decide if its a boot or a fish however. Disclaimer: the speed at which the wave travels is a lot faster and was just given as a simplification in this scenario. The approximate speed of sonar in water is 1500 meters per second and the fish finder sends out many pulses per second to scan the seafloor continuously resulting in the rolling image you see on the fishfinder. Edit: a word" ], "score": [ 6, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "givj9s4", "givj7yr" ], "text": [ "Structural integrity. It's a cross rib to ensure that the pressure combined with the high temperature doesn't cause it to break. It's not really two chambers, it just looks like it is.", "In plastic lighters, it's not so much that it's getting divided but rather that it's getting structurally supported. The divider is a web of crisscrossed struts that reinforce the integrity of the lighter, whose contents are under a lot of pressure. You would never want, say, a lighter to explode if you left it outside in the hot sun. This is what prevents it from doing that." ], "score": [ 130, 62 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giwbgx0", "giwbyx4" ], "text": [ "Your phone isn't watertight. Water will work its way into your phone by water pressure (if it's dropped into water). Conceivably, capillary action can also do this, but I'm not sure how commonly this would occur.", "Simply put, water will enter through any available hole, even holes that your naked eye can barely see. If your phone isn't water-resistant, that means it has no gaskets or o-rings that seal out water, making it easy for liquids to enter. If it's water-resistant, the phone will generally be gasketed (typically, a rubber joint that binds body surfaces together to prevent water or air from entering) on the inside to prevent water ingress, but if you submerge the phone at a depth beyond its rating, the water pressure will be able to squeeze past said gaskets, and enter the phone." ], "score": [ 4, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giwr5iz", "giwri0b", "gixhgtp", "gixlkjn", "giwy7ou", "gixngh8", "giyg6nk", "giy6yaa", "giyjfia" ], "text": [ "In the strict sense, a \"cog\" is a tooth on a wheel. A cogwheel is any wheel with teeth. A gear is a cogwheel used to mesh with another cogwheel. And a sprocket is a cogwheel that links to another cogwheel by means of a chain.", "A cog is a tooth on a wheel. When two cogwheels mesh with each other, they are called gears. When a cogwheel works with a chain (and some sorts of toothed belts), it's called a sprocket. The remaining applications that use cogs may only have one or two on a wheel, so that the interaction is intermittent, or involve other mechanisms like a ratchet or track.", "Since it’s been explained already, the way I like to think of it as a gamer is: In the game Gears of War each solider is called a cog and as a team they’re called gears, which is actually a pretty good analogy. Basically gears are made of cogs.", "One is the Coalition of Ordered Governments, the other is the colloquialism for their frontline infantry. /s", "A cog can be any spinning wheel with sticky-outy bits which pushes against another wheel with sticky-outy bits so that they both spin together. A gear is a special type of this mechanism in which the sticky-outy bits are specially shaped so that at the point where they touch the two pieces *roll* against each other rather than *sliding* against each other, as cogs would do. Rolling generates less friction than sliding, so this special shape is more efficient at transferring power from one wheel to the other. This special shape is called an involute.", "so whats better a cogswell cog or a spacely sprocket?", "The Coalition of Ordered Governments is the one the many governments on Sera and the only to kinda survive the locust invasion. Gears are their soldiers.", "It's quite simple really the COG is short for \"Coalition of Ordered Governments\" and the Gear is the soldier within their military. Usually dispatched against UIR Troops \"Union of Independent Republics\", later after the pendulum wars and just a short few weeks later E-day happened and the COG had to mobilize against a new threat known as the Locust Horde.", "A cog is used to transfer motion from one point to another, a gear is a type of cog used to change the speed of rotation (or I might have completely made that up)." ], "score": [ 22684, 557, 122, 28, 20, 9, 9, 9, 3 ], "text_urls": [ [], [], [], [], [], [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gix5wlk", "giwsc2j", "giwsf0s" ], "text": [ "Drill two holes in the bottom of a bucket. How does the bucket provide water to each of the holes? Because they're all connected to the same body of water. Drill three more holes and more water will come out - as long as they're all at the same height they get the same amount of water. Power strips do the same with electricity - all of the sockets are connected to the same supply so they all get power.", "The power bar is basically a splitter, it's taking all the power in through one cord and dividing it out among the outlets. They are limited to the amount they can flow through the main cord, and to the capacity of the circuit they're connected to. Going the other way, to each connected device the power bar \"looks like\" the wall plug...they can't tell. The power bar just adds all the power demands from all the connected devices and that's what it pulls from the wall. If you try to draw too much power through the power bar, it will either trip its own internal circuit breaker (to protect the power bar) or the main circuit breaker will trip (to protect your wall wiring). The power bar does \\*not\\* change the power capability of the main circuit, it just gives you more outlets to plug into.", "Power doesn't get \"divided.\" Everything on a circuit draws the current that it needs, until there's enough load on the circuit that the breaker flips. Take a circuit with nothing plugged in, with 120V potential. Plug in a 500W device. Current is power divided by voltage, so 500W/120V = 4.16 A. You now have 4.16 A of current on that circuit. Plug in a second 500W device, you now have 8.32 A of current. Plug in a third, 12.5 A. Plug in a fourth, and you flip the breaker because the breaker will only allow 15 A before it flips." ], "score": [ 17, 17, 8 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giy5o16", "giy8ivn" ], "text": [ "They measure the difference in height of ground levels. I don’t think they’re cameras - they are basically sniper scopes that have levels in them so they can point at their buddy’s ruler. If the viewfinder is on a 4 foot tripod, and the viewfinder, while pointing level, hits your buddy’s ruler at his 5 foot mark while it touches the ground, you know precisely the height difference between your two points is 1 foot. [Here]( URL_0 ) is a cool video that explains it in a neat way.", "Ok, so having done some surveying..... Up until a few years ago you would have seen two two or three people out on these crews - typically a surveyor, taking measurements, and a couple (or more) rod-men, with tall poles in their hands moving around. The surveying instrument is called a theodolite (there is a simplified version called a dumpy level, but that is for a specific purpose, not surveying) and the surveyor can look though the monocular telescope at the rod held by the rod-man and measure both azimuth (angles around the compass from 0 to 359 degrees) and elevation (in plus or minus degrees) from his/her current position. This combined with distance (used to be a surveyors chain!) gives, with enough points taken, the ability to draw a map that includes surface contours. All of this work is \"tied\" to a local known point known as a \"benchmark\", and ideally more than one to improve accuracy or gain \"closure\". If after a days work you do not get closure to within the specified accuracy for a job, its out to correct the error of your ways over the same ground the next day! More recent advances bring an instrument known as a \"total station\" that is a theodolite, distomat (laser distance device), high performance dgnss (global differential satellite navigation system) and a whole pile of automation all wrapped into one that does the surveying for you. It can locate and lock onto a prizim on a rod pole, and \"all\" (ahem) that is now required is someone to walk around with a rod and prizim and a remote button to capture each point of interest - the total station having azimuth and elevation motors to track the rod and prizim. If you ever drive or walk past one of these total stations at work you can watch it tracking and blinking its little red \"headlight\" as it works and the rod man - surveyor goes about his/her work. Oh, and other than taking photos for interest and to write up field notes, typically surveying is a camera-less sport. Aerial and satellite mapping and photography are used to provide terrain feature detail." ], "score": [ 13, 4 ], "text_urls": [ [ "https://youtu.be/SPCewaAfqPA" ], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giyebzq", "giyh2bd" ], "text": [ "The main problem with the concept of vacuum airships is that, with a near-vacuum inside the airbag, the exterior atmospheric pressure is not balanced by any internal pressure. This enormous imbalance of forces would cause the airbag to collapse unless it were extremely strong (in an ordinary airship, the force is balanced by helium, making this unnecessary). Thus the difficulty is in constructing an airbag with the additional strength to resist this extreme net force, without weighing the structure down so much that the greater lifting power of the vacuum is negated.", "It would float, but it's incredibly difficult to build a pressure vessel that big holding that much pressure, so you'd have to make it really heavy and then it wouldn't float. If you're using some kind of gas, the balloon isn't trying to hold much pressure; it just has to be strong enough to hold its own weight." ], "score": [ 20, 5 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giysxju", "giyshpj", "giytnft" ], "text": [ "A couple of reasons: 1. Cars (internal combustion engines) need air for combustion. Without air, combustion cannot happen. 2. Cars are huge air bubbles, which mean they float, at least before the interior fills up. Even then, there will be air pockets like in the fuel tank. 3. Some of the electric circuits aren't waterproof, for example the fuse box, which might short everything and stop stuff from working. 4. Even when everything has filled with water and your car dips into the bottom, the water creates a lot of resistance, combined with sand in the ocean floor, you might just spin the tires in place. 5. The engine can only handle so much backpressure on the exhaust. With water pressure pushing in, the engines will struggle to push out exhaust gases. 6. The tires are filled with air, which will deflate under high pressure (like in the bottom of the ocean).", "Combustion needs fuel and air. You drive into the sound, you run outta air. Cars can be equipped with a snorkel to solve the air issue.", "The engine wouldn’t work - it needs air for the combustion to occur, the metal casing might crack from the sudden cold water, and the cylinders would fill up with water. Even if you enclosed the engine system, and sealed the car from water getting in, you would need a different propulsion system, as the tyres wouldn’t have enough traction to push the car forward. Even if you resolved those issues, you then have to deal with uneven sea floor, and the added pressure as you go deeper, in which case you’d probably be better floating either on the surface or submerged like a submarine, so you’d need ballast and the ability to sink and float. Then, you’d run out of fuel a few hundred kms from shore, so you’d need a much bigger fuel tank, bigger batteries, more navigation equipment, on-boats toilets, and sleeping quarters. Then you’re going to need supplies and a galley to cook in. You’d need at least three Honda civics joined together to fit all of that." ], "score": [ 33, 6, 5 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giywbcf" ], "text": [ "New builds will generally (not always) require an architect or engineer. There is not usually a requirement that they design the appearance as well but often times they will as a part of managing the whole project. Engineers and/or architects are required for new builds to ensure structural soundness and energy efficiency. Down the road, when a remodel is started, the jurisdiction having authority (JHA) usually a code department, will require a permit to be issued and inspections completed for any project relating to the structural integrity or insulation envelope of the home. Local law will generally require this. Those updates and improvements will be required to meet the standard of when the home was built or better. That said, many home remodels are done without a permit. Logistically it's just too cumbersome to monitor every project in every home to see when the scope goes from cosmetic to structural. However, new builds are easy to spot." ], "score": [ 3 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "giznbwc", "gizkg4t" ], "text": [ "Well they are simply a mesh with small enough holes so bugs can't get through. But wind still can, so you can still cool your house off without letting bugs in.", "It depends on the technology but the most common type of screen today is an LED backlit LCD. These work by having a white LED light source at the back of the monitor, this then shines through a layer of liquid crystal filters arranged in an grid of pixels, with each pixel having a red, green and blue filter. The amount of light these filters block can be varied by applying electricity to them. When all the filters are off you get white, when they’re all on you get black." ], "score": [ 11, 6 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gizvu6a", "gizw58q" ], "text": [ "The gas is lighter then air but the airship is heavier then air. So together they are just as heavy as air. The exact weight of the airship can be adjusted by either releasing gas, refilling the gas from bottles or dropping ballast. But most of the time the altitude can easily be controlled by changing the pitch of the airship using the elevators in the tail and then use the engines to go up or down depending on the pitch. This is very similar to how an aircraft changes altitude.", "~~Thy have ballast chambers called ballonets which, attached to an air pump, can be pressurized or depressurized. This changes the overall buoyancy of the ship. If you pack the ballonets full of pressurized air, the airship will sink. If you vent them, it will rise.~~ a person with flying experience tells me this is incorrect, please disregard!" ], "score": [ 11, 4 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gj0cgxk", "gj0fa1a" ], "text": [ "Salt really accelerates corrosion, but the corrosion will really only progress when exposed to oxygen and there's a lot more oxygen in air than water By taking the box out of the ocean and putting it into a bucket of water they keep any innards which may have been exposed to salt water from being exposed to air which will provide the oxygen needing for the corrosion to progress. When it gets to its final destination it will be removed from the water and then cleaned, but you don't want it to spend a few days traveling and degrading because its exposed to the air.", "The flight recorders usually get badly damaged by the crash. So the recovery crew would be unable to read out the data but have to ship it back to labratories that can carefully disassemble it and repair it to recover the data. However the recovery crew needs to package it in such a way as to prevent further destruction. If the flight recorders have been exposed to ocean water then we know that anything that does not handle water is already damaged. But there are things that can not be exposed to air, it can be that it rusts or it can dry up and become brittle. So keeping it in water is much safer then drying it out in air. Furthermore the salt in the ocean water can be very corrosive and cause chemical reactions over time. If you leave the ocean water in place or even if you let it dry then the salt will continue to do damage. But flushing the flight recorders out with fresh water will remove the salt. This leaves the flight recorders in their most stable conditions for transport to the labs. Recovery crews will even try to bring destilled deoxygeneted water which is extra stable. This is not that different from the water at the bottom of bogs which can preserve bodies for millenia. So the flight recorders should be safe in the few hours it takes to get it back to a proper lab." ], "score": [ 109, 17 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gj3gxqv" ], "text": [ "Politicians like to spend money on short term solutions on a local level. In my town we could use divergence lanes and ramps to ease traffic flow but what we get it stop lights. Politicians that want to be re-elected don't want to be known as big spenders so they take the cheap options when they can and putting off infrastructure is always cheaper that spending on things that don't make money right away. In the US, if a State route goes through your town the state or the Federal Government will help the city with the cost of roads and bridges. If the highway runs across multiple counties, the state can apply for Federal help with the projects. Federal funds come form Capital Hill and are allocated out of the yearly budget. First you have to get proposals done. Then impact statements, traffic flow studies, feasibility studies and cost projections. These can be expensive. Then contractors have to put in bids, the bids have to be reviewed and then the contracts awarded. This can take years. The money then needs to be available to pay for the contractors to start work. When politicians are \"balancing the budget\" that means infrastructure funds usually go bye bye. Then the whole process has to start over. Meanwhile, the Pentagon gets $690 billion dollars a year and doesn't have to explain anything until years later." ], "score": [ 3 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gj4cz2o" ], "text": [ "It's not a gyro, it's a very low friction gimbal supporting a pendulum. Body harness gives a strong stable anchor point for the \"arm\". The arm has springs and bearings to balance the weight of the camera to effectively make the camera zero g. The big bearing around the camera shaft is very low friction so the camera tends to stay stable in space as the operator moves around it. And the camera \"stick\" is weighted at the bottom so the camera wants to stay vertical regardless of what the arm does. Basically, the frame is a big kinematic mount that allows the camera to move freely in all directions and uses springs to null out gravity, so the camera stays steady in space because it behaves like there's no external forces or torques acting on it." ], "score": [ 3 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gj5xdu4", "gj5cz95", "gj6bb8k", "gj5d9jk", "gj606fp", "gj7j2w7", "gj68fc0", "gj78lov", "gj6iah1", "gj7z3oi", "gj6d5sg", "gj71ijf", "gj7ge8f", "gj629gr" ], "text": [ "Absolutely nothing. They are just manafacturing artefacts, either injection ports, or air escape ports, rubber stays behind when the tire is removed from the mold. They do no harm, they usually wear out after a few miles, and everyone's happy. Manafacturer didn't waste time/manpower to remove something that's completely irrelevant, and the customer gets an indicator that the tire is brand new. EDIT: Thanks for the rewards and the upvotes. To add some more info from people who actually work in tire industry down below: these are air vents, so that when the tire is shaped against the mould, air can escape, and due to pressure some rubber starts pushing out also. This is not universal to all tires, some use a different mould that does not leave these artefacts.", "They don't have a purpose, they are just leftovers from the manufacturing process. As rubber is injected into a mold, there are vent holes that allow air to escape, so no bubbles end up within the tire and weaken it. A little bit of rubber goes out these holes as well, producing the hairs you see on the tire.", "They are called vent spews, they are a byproduct of tire manufacturing, small vent holes in the mold so trapped air can find a way out. They don't do anything, however, they are a signal that the tires are NEW :))", "They don't really have a purpose. They're just little extra bits of rubber from the tubes they squirt liquid rubber into the tire shaped mold.", "on a motorcycle they point out how much angle you leaned in curves. not sure if that is their purpose tho", "Basically they take a “green” tire (which means it is uncooked) place it inside a press with a mold (VERY hot), a bag fills up with air and presses the green tire from the inside outward making it touch the hot mold giving the tire’s tread and sidewall its shapes and writing. The basically molten rubber makes its way up into holes drilled into the mold intended to let air escape from the tire. Source: worked for Michelin for years as an engineer.", "When I was a little kid my uncle told me they were to soften the tires in case they ran over animals hahaha", "There is no purpose, they're just leftover bits from when they pumped the rubber into the mold.", "Huh, I legitimately thought it was a thing where it was bad to shave them off or get rid of them. Must have gotten bad info, interesting that they serve no purpose, but I’m oddly kind of happy that’s the case!", "For bicycle tires, they're there to remind you that the bike you bought two years ago to get in shape hasn't been used enough to even wear out the nubs. Seriously, how are the center nubs still there? I think they're even growing I've used that bike so little.", "The hairs are leftover from the mold process, they're the little excess that's left out. However, they do have a little, almost in-significant role of proving a tire's freshness. They get worn out pretty quickly, so if they're gone, the tire has been used. Of course, used to a very minor extent, else you can see the wear with your eyes. That's not intended, but it is a use.", "Everyone else has thoroughly answered your question, so let me chime in with a bit of obsolete tire trivia that is relevant here. In nations with lots of heavy snow, tires with metal studs in them are common. In Canada and the US though, such studs are often not allowed because they damage the road surface of paved roads that have been properly plowed and salted. As a compromise, for a long time tire makers offered rubber studded tires. These looked like standard snow tires, but every block of rubber had numerous rubber \"whiskers\" about 1\" long by maybe 1/8\" in diameter. These offered you better bite in the deep snow without damaging the roads in clear conditions. [HERE]( URL_0 ) is a link to an image that shows a Norwegian snow tire that has both kinds of studs, rubber whiskers and carbide studs There were two problems with them however: 1) They were much noisier than standard winter tires. Making every busy highway that much less pleasant to live near 2) They made the cars of the 70's even more fuel hogs than they already were. So, here in Ontario at least, metal studs were banned in the early 70's and the rubber studded ones were banned in the late 70s. As a side effect of this, late 70s and early 80s playgrounds suddenly sprouted tire swings using brand new tires that now could not be sold.", "I always thought they were made for extra grip offroad, but everyone else says otherwise, because we always used to have 2 cars when i was young, and dad had these “hairs” on the tires for his 4x4.", "To add to all the other comments... I had a dealership tech once comment that I was likely easy on my vehicle because after 1.5 years most of the hairs were still there. Lack of those hairs on a newish vehicle could indicate poor parking and lane tracking (rubbing curbs) etc. Not a purpose, but an observation." ], "score": [ 9210, 8044, 28, 17, 12, 8, 6, 5, 5, 5, 5, 5, 3, 3 ], "text_urls": [ [], [], [], [], [], [], [], [], [], [], [], [ "https://images1.americanlisted.com/nlarge/nokian-hakkapeliitta-w106-26x1-75-studded-snow-tires-40-allentown-americanlisted_28393113.jpg" ], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gj5kypg", "gj5kojk" ], "text": [ "They don't. They either have no knowledge of how old the oil is, or there is a setting in the cars computer system that mechanics reset when they perform an oil change. There might be ways to automate it, such as an RFID built into the oil filter (assuming you change it when you change oil) that the cars computer can detect when it's removed and replaced, and make an assumption that the oil was changed.....but there's no magical way for a car to measure oil life on it's own.", "Based on the date (if the ECM monitors it) and the mileage. On most vehicles, if not all, that's all it is. When the oil is changed the timer is reset, once the vehicle hits the pre-programmed mileage or date, the oil life indicator drops a certain percentage." ], "score": [ 4, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gj6hgad" ], "text": [ "It’s called hydromulch which is a sticky liquid that contains seeds and aids in erosion control. Forms like a hardened surface that’s less likely to scour out. I think it’s coloured green so it’s easy to identify what areas have been sprayed [Hyrdoseeding]( URL_0 )" ], "score": [ 3 ], "text_urls": [ [ "https://en.m.wikipedia.org/wiki/Hydroseeding" ] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gj6jimn", "gj6jo4f" ], "text": [ "The curb is made first, Generally before the road. Also: Everything is separate so that when there is settling, it’s going to move along the cracks.", "Curb and gutter are often slipformed with a unique machine. It's quicker than hand forming C & G and the sidewalk is easy to form. On concrete roads, integral curbs are often used. Also buffer zones are usually wanted if space allows. For pedestrian safety." ], "score": [ 7, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gj7hfop", "gj7ib2y" ], "text": [ "When you get close to pointing straight up, the \"lift\" from your wings is actually pulling you sideways, and it's the thrust from your engine(s) that's counteracting gravity. In that attitude you're flying more like a rocket than an airplane. To keep that up, you need a thrust-to-weight ratio a little greater than 1. (Equal to 1 won't do it; you have to overcome your drag as well as your weight.) I think the F-15 Eagle was the first American fighter, and maybe the first jet in the world, that could sustain a vertical climb - F-4 couldn't, F-14 can't, F-16 and F-18 can.", "An airplane flying straight up has its full weight supported by its engine. This can only be achieved by aircraft with monstrously strong engines - engines that can output more thrust than the plane's weight." ], "score": [ 10, 6 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gj7o0jo", "gj7ohcc" ], "text": [ "It is to make the structure stronger. Circular shapes are very strong. Try to put some books on an empty toilet paper roll. It can take a lot of weight.", "If you take a piece of paper and try to bend it in two different directions at once you will notice that it does not work. You can bend it one way or the other but not both at the same time. It is the exact same thing with sheet metal as well. By intentionally adding creases in the metal they are making it stronger. This means they can use thinner pieces of sheet metal which saves them money. The machines usually do not rely on the strength of the side panels and in some configurations they might omit them entirely. However they do need to prevent them from making noises so they need some structural integrity in the panels. And they usually need to add some creases anyway in order to make mounting points for the panels. The way they make these creases is by using a big press to stamp out the sheet metal and create the creases. So it does not cost them much to just include a few more of them for structural rigidity." ], "score": [ 5, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gj9bosl", "gj9btsc", "gj9bwoa" ], "text": [ "Sights and scopes on guns are adjusted so that the shot lands where the sight is indicating at a set distance. This is called \"zeroing\" If you zero your sights for 400m then the bullet will hit on target at 400m. Any closer and the hit will be high, any farther away and it will be low. [Here's a simple illustration]( URL_0 ) that shows how things work.", "When you install a scope, you alter the pitch of the scope with the little dials on the side/top. You keep adjusting and taking shots at a target at a fixed distance until the center of your scope lines up with that distance. This is called \"zeroing\". If you need to shoot further than that, you aim above the target. If you need to shoot shorter, you aim below the target. Most hunters \"zero in\" at between 50 and 100 meters, just based on what they're hunting and their assumed distance. Long-distance shooters generally go to 200 meters. Extreme distance shooters might go to 400 meters.", "You zero the scope. Go to a range. shoot the target while resting your rifle on a sandbag or such. Without moving the rifle adjust the knobs on the scope until the cross hairs are on the hole." ], "score": [ 11, 5, 4 ], "text_urls": [ [ "https://i.stack.imgur.com/39ptH.jpg" ], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gj9ymdo", "gj9zd7q", "gj9zokk" ], "text": [ "You can have chemical breakdowns from overheating the oil, but usually what happens is dirt and wear particles start accumulating in the oil, and because of the close fits between moving mechanical parts, those dirt and wear particles scratch parts, and create even more wear particles. The oil filter catches some of those particles, but over time you get enough wear particles and you start scratching everything up, and oil starts leaking. So, it's better to just drain the oil, change the filter add new oil, and stop that fail cascade from getting started.", "A couple of things are happening with your oil. First it simply gets dirty. Dirt, and grime are constantly getting cycled into the oil. Worse sometimes other car fluids will as well, which can lead to the oil breaking down. But even without those things, the oil will eventually oxidize. Much like metal rusts, the oil will constantly be under a slow moving chemical process that changes the nature of the oil. The combination of these factors leads to sludge building up in the oil. This, in turn, makes the oil less effective. The oil is there to reduce friction and wear and tear on the engine. So if you don't spend a little time and money replacing the oil, eventually you are going to spend a lot of time and money replacing engine parts instead.", "When you heat up oil it will start to slowly decompose. So what would be nice lubrication oil turns into dry sot and thick tar after a while. And when your engine is cold as you have just started it the fuel does not burn right and forms a lot of sot, which gets washed away into the oil as well. Another issue is that when parts wear it erodes away tiny pieces of metal. This metal also gets washed away in the oil and can act as sand paper which further wears down the engine. The intention is for the oil filter to capture all of this but it is not perfect and some will get passed the oil filter. And if the filter gets clogged then the oil is not able to get to the parts it needs to lubricate. It is possible to skip some oil changes. Sometimes you get lucky and the oil does not get as bad as quickly. But most of the time it will just cause more wear on the engine then usual and you reduce the lifetime of the engine and reduce its performance. But because oil is so much cheaper then engine components most prefer to do a few oil changes too many then too few. This also gives you a chance to inspect the engine. A lot of engine problems will change the look and feel of the engine oil so you might be able to spot some issues before they become major." ], "score": [ 23, 6, 4 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjaby7j" ], "text": [ "It's adjusting torque. If I turn one wheel at 100 RPM with 10 ft-lbs and one at 100 RPM with 90 ft-lbs, I'm sending 90% of the power to the second wheel. Modern systems that can dynamically split torque around are usually AWD (4WD usually refers to systems that either send equal torque to all wheels, locked diffs, or conventional un-controlled diffs). By applying brakes to individual wheels (or sometimes adjusting the diffs on the fly) they can alter the torque split that's getting to the wheels, which splits the power. When the brakes come on unevenly, the RPM \\*isn't\\* the same (that's the whole point of the diff) but big power shift is the torque." ], "score": [ 7 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjb9d8s" ], "text": [ "This can be the breaking of rust bonds, which is especially common on cars. Sometimes you can heat the bolt with an oxyacetylene torch to help with this as well." ], "score": [ 6 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjbmf2r" ], "text": [ "In a manual transmission cars, they do as long as you don't engage the clutch. The crankshaft engaged the input shaft in transmission gears and then goes to output shaft and the differential then the axle and the wheel. In automatic transmission cars, the clutch is replaced by a torque converter which allows some slip before engaging the transmission input. Your description more matches cvt cars, the transmission is constantly changing gear ratio to make \"good fuel efficiency\" so your engine rpm might stay same while wheels spin faster" ], "score": [ 8 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjbwiyk", "gjbt8j8", "gjbtu8t", "gjcjp8f", "gjcm824", "gjc3tib", "gjdgua8", "gjcail9", "gjcl4xp", "gje73cm" ], "text": [ "Take a big coil of wire - a metal, full of electrons. Electricity is just the movement of electrons. Because electrons are electrically charged, they create and respond to electric fields - think of when you rub a balloon against your hair, statically charging it. The hairs push away from each other. That's the negative charges creating negative fields. Negative charges don't want to be in other electrons' negative fields, so they start pushing away from each other. A magnetic field is the same thing as an electric field, really - that's why we call it \"electromagnetism\". The only difference is how you look at it. Put some magnets in the centre of the big coil of wire. The magnetic field from those magnets will start to push on the electrons in the wire. If you start turning those magnets, the field will turn too - and as it moves, it'll push the electrons with it. Because it's a coil, or a spiral, as you spin around the middle, you also move to one of the ends. The electrons moving out of the end of the coil is electricity. Edits: Literally a hundred comments later asking the same few questions: 1.0) You can't deplete a wire of its electrons. Electricity works in circuits, closed loops of wire - as you push the electrons out of the wire, the pushing force affects the whole circuit and more electrons are pushed back into the other side of the coil, and they then get pushed around again by the magnets. 2.0) The electrons start in the wire. Everything is made of atoms and atoms have electrons. In metals, those electrons are free to move around, but they're more bound up in non-metals. 3.0) You can find naturally occurring magnets in the form of minerals like magnetite, or lodestones, but you can also make them by rubbing two pieces of iron together in the same direction a few thousand times. 3.1) \"In the same direction\" means the strokes are always the same, you don't go back and forth. Think of it like combing your hair: you always brush in the same direction. 4.0) I know this is an oversimplification, that's the point. It's an ELI5. Stop telling me \"Well actually it's a lot more complicated-\". I know you can carry charge through other means, not just electrons; I know positive charges are conveyed as holes in the electron sea; I know. Whatever your correction is, I know, and I deliberately left it out to make it simple enough for a 5 year old. As is the sub's reason to exist. If your 5 year old can crunch the numbers on Lenz' Law, good for you, go breed an army of your fucking superkids and stop bothering me. 5.0) Really late in the game here, but: \"In OP's comment he says-\" - no he doesn't, _she_ does.", "There are a bunch of ways. Silicon-based semiconductors will be quite beyond a medieval peasant so getting it from light is out. Mechanical is dead simple tho, get a magnet, get a metal wire, move one across the other fast, BAM you induced voltage. If you cover the wire in insulator (paper, wax infused thin cloth, etc. work fine) and make a tightly wound coil, the effectiveness of the generator skyrockets. Do whatever for energy source, steam machine, water wheel, windmill, a serf running really fast in circles holding a crank. You can also make a chemical battery, only needs two different metals and something acidic to dip them into.", "The most common way is mechanically. A generator spins coils of wire inside of magnets which generates an electrical current. We use generators in nuclear power plants, coal power plants, wind turbines, etc. Wherever you have something spinning there’s a generator attached that generates power. Another way is photovoltaically. Solar panels are made of a special material that generates power by exciting electrons which jump between energy states which generates electricity. Electricity can also be made chemically. A substance that wants to get rid of electrons is paired with a substance that wants electrons. This is commonly known as a battery. When the two substances are connected via say a wire, the electrons flow which produces electricity. The short answer is there are a number of ways to do it and it can become very complicated trying to explain it all but I think those are the basics.", "Gonna attempt this. Electricity is what we call it when electrons, a tiny part of atoms, that make up everything, move through a thing (usually metal or \"electrically conductive\" material) We can make that happen many ways, like rubbing two things together (static electricity from rubbing a balloon on your head), a magnet moved by a coil of copper wire (electro-magnetism). When we make these electrons move, we call certain parts of that movement certain names to make things easier, voltage is how many electrons want to move through a wire, amperage is how many is moving at once, and ohms are how hard it is to move them through a thing.", "Late but whatevs. I WANT to offer an answer so I'm gonna.. Electrons in wire are like water pressure in a pipe. So first, let's look at how water moves, flows, and behaves. Water is not compressible. You put it in a balloon and deform the balloon, and it will have the same volume as before, just in a different shape. Air? Not so much. Try putting a balloon full of air in the fridge if you don't believe me. This is important to the analogy, because electrons in a wire can't be compressed either. So if I were to take a long pipe, fill it full of water, and shove hard on the water, the water in the pipe would push on the other water, until it came out the other end with the same force I shoved with. Now, electrons have regions around the atoms that they will be hanging around, as a function of their Energy Level. Some atoms, like those of conductor materials, have electrons that are rather easy to shove into their neighboring atoms. But any atom can only sponsor so many electrons at once in any particular region, and some regions are very hard to get shoved to, requiring great force, just like a section of pipe can only hold so much water, and if you put too much in you may swell or even burst the pipe. So, now that you are thinking of pipes, *the wire acts as a pipe for the electrons*. Finally, electrons are influenced by magnetic fields. If you see a magnetic field, that is the product of a moving electron... Though sometimes the field is created by spinning more than moving per se. If you generate a magnetic field around a wire, you are shoving the electrons in it because when a magnetic field changes, electrons are changing. So by moving a magnet across a wire, you push on the electrons. If the wire doesn't have a \"closed circuit\", you will have a hard time of it because there is nowhere for you to push those electrons and they will swirl around like water in the pipe, just making it hot. If the wire creates a closed loop, you just shove the electrons around the loop. Shoving electrons around, by changing magnetic fields around them, specifically to create this turbulent motion of electrons, is how induction heating works. In addition to being able to actively \"pump\" electrons through the wire \"pipe\" using a magnetic field, you can also do something akin to putting a water tank on your roof and letting gravity draw the water through the pipe. This is how batteries work, though the force that draws the electrons \"down\" through the \"pipe\" is still electromagnetic: one chemical has electrons and is separated from another chemical that wants them. They want to exchange electrons (this is how most chemical reactions work!), And by connecting the ends of a wire to each pool of chemical, you allow the electrons to flow between them, from where there are \"too many\" to a place where there is \"too much\". Finally, how do we get work done with this arrangement? Well, you know how I said shoving around electrons causes the magnetic fields to change? Magnets can pull on other magnets, and you can make a magnet exist (or not!) By whether you are moving electrons around. Want to create a magnet temporarily to pull on a bit of iron? Shove some electrons through a loop of wire, and you can pull on stuff! Install another coil, and you can pull it back the other direction (or to the center) depending on which coil you shove them through, such as \"both\". Want light? Shove the electrons through a tiny space, and they will be forced to \"crowd around\" and get shoved up to higher energy states than normal, and then when things calm down a little for them, they will pop back down, and the distance they move (moving electron) creates a moving *wave* in the electric and magnetic fields, and that's what light is! For the lazy: Spinning electrons are magnetic. All electrons \"spin\". Therefore all electrons are magnetic, and can be shoved with magnets. Metal wires have fixed electron counts, but you can shove them around inside the wire, because magnets can shove other magnets, and as a result, you can express that magnetic force that you shove into the wire elsewhere along the wire to do work.", "Seeing the ansewers, where would I find a magnet in the medieval times? How can I make one?", "Here's a major oversimplification of it I've split the explanation into 4 parts: - Atoms - Electricity - How the light bulb works - TLDR First off, atoms and what they're made of: Everything in the world is made of atoms, but what are atoms made of? Well we have 3 parts of an atom, neutrons (a particle without a charge), protons (a particle with a positive charge) and electrons (a particle with a negative charge). We call these subatomic particles, because they're a step below atomic particles like atoms. (There's a step below subatomic particles, but that's a whole other can of worms). Now protons and neutrons really like each other so they're stuck together in the center of the atom while electrons are only loosely attracted to the other 2, so they orbit around the center like our satelites do around earth or the planets around the sun. Different elements are made of different amount of electrons, protons and neutrons. It takes a lot of energy for protons to be separated from the neutrons in the center, but a loooot less energy to move around the electrons, cos you know they only kinda like being near the center of the atom and not mooshed together like the proton. Here's where we actually get to electricity: All energy in the world is transformed, not created. Everyday we see things like a light bulb taking electrical energy and turning into heat and light, or a car turning combustion (heat, light, expanding gas kinetic energy, sound vibrational energy even) into mechanical kinetic energy that makes it go vroom. Now electricity is a big branching word we use to cover energy that's created using the movement of electrons jumping from atom to atom. There are many ways for electrons to be influenced into moving, but we won't go into that detail cos it's quite literally a 1/4 year high school topic. One of the most popular is to create a positively charged deficit so the negatively charged electrons will start moving towards it, cos we're gonna tack on the fact that everything in the world also likes to be balanced and in equalibrium. We see this in batteries, that's why we have a positive end and a negative end,the battery has chemicals and things in it that have a tonne of electrons on the negative side, but a lot less on the positive. When you attach the battery to a circuit,the electrons see a path for them to run through to the positive side so they scurry through the circuit to try to balance out the battery and become equally charged on both sides. Another way to move it is glorious magnets. At some point in time in the past after many years of research and discoveries, we found out that magnets effect electrons. Now I'm not gonna dive into it,cos electromagnetism is a whole topic with a super interesting history involving people who's names are still used in words today like, voltage, amps, Faraday cages, galvan etc. All you need to know of magnets effect electrons so we made things to push them around like electric motors and such, google may give you a much better explanation than I ever could haha. Now finally an example of electricity at work: The light bulb, I've already explained how electrons want to move through circuits because of something like a battery, but why does the traditional light bulb do what it does? The traditional light bulb is just a thin cable, enclosed in a glass bulb, filled with non flammable gas. That's it, why it took Edison so many attempts to come up with it is baffling, but anyway. When you have a electrons running through it,several things start to happen. The first is the thin cable,being so thin the electrons coming in through the thick cable outside of the bulb have to squeeze through, but because of another scientific principal, it has to go faster in a tight space to make sure the same number of electrons come out the other side. This means they've a lot faster in the cable. When this happens, it causes a lot of friction. (Did he say friction?!?!?) YES, friction can be created from electrons,but at the speed they're moving at it very quickly transforms the it into heat energy and light energy. That's how it works, something to note is that non flammable gas we mentioned earlier is there to make sure the thin cable doesn't start a fire from the heat and melt itself. Combustion requires oxygen,so the bulb is filled with a gas that is not oxygen or otherwise flammable, in case someone breaks the bulb. TLDR: Electricity is what we call the generation and usage of energy when we manipulate subatomic particals called electrons.", "A copper atom has roughly 29 electrons orbiting around a nucleus, just like planets around a sun. However, they are arranged in several layers. The inner three orbits (*shells) have 28 electrons. And the outermost orbit/shell has only one. That one electron is held to the atom by a weak \"gravity\" of sorts. It can easily be pulled away by a strong magnet. If you were able to line up in single file a row of copper atoms, and then pass a strong magnet over them, it would force that \"loosely held\" outer electron to jump from one electron to the next. The atom just behind the sweeping magnet would only have 27 electrons, and the atom just under the magnet would have 29 electrons. They would both be experiencing an electromagnetic imbalance, and the atoms would experience a force to go back into balance. Each nucleus in each copper atom has 28 protons at the center (the sun) exerting a force that tries to have 28 electrons around it. The copper atom with 27 electrons is trying to grab one, and the copper molecule with 29 electrons wants to get rid of one. Once you take away the magnet, all the copper atoms go back to a system that is balanced, 28 protons at the center, and 28 electrons orbiting them.", "There's an anime called Dr. Stone where in the modern world, every human on the planet was turned into stone after a mysterious flash of light. This story tells of how some people from the Pre-Petrification World try to rebuild civilization in the Petrification Age, the Stone World. It shows the \"basic' steps of how to make a electricity, re-create wine, soap, gunpowder, and even a cell phone. He also makes glasses for a near sighted character. I would suggest giving it a watch!", "I will try to explain it in a way that a human eye can actually see it. Unfortunatelly you will need to imagine a bike, so it won't be *that* useful if you go back to Medieval Period. Imagine a bike. More precisely, its gears and chain system. When you use your foot to push a pedal the front sprocket rotates. It pulls the chain with its teeth. Chain is essentially a lot of small, metal circles connected together, so they \"pass the force\" until the rear sprocket takes it and moves the rear wheel. That's how you transformed a force of your feet into rotation of the wheel. Now let's take everything into electric world. Chain is the wire. It is built from a lot of small circles, electrons. If you apply the force to one of them, they will all move along and \"pass the force\" to another device. To apply the force we use magnets. Magnets can push and pull electrons just like sprocket pulls the chain. You have all the pieces! You can actually picture a small cogwheel mechanism inside your TV/computer/lightbulb that is \"pulled\" by the \"chain\" that runs from the power plant and you connected to using a plug. The power plant \"pushes the pedal\" (creates electric energy) to \"rotate rear sprocket\" (make the lightbulb shine). So how do we start? Well, some time ago people were looking at certain stones found underground. The analogy to cogs is - some stones had teeth, some were round with zero teeth (like a round disk). So naturally the one with teeth could be used to pull a chain (natural magnets). We took them, made some experiments and we used them to create first \"chains and sprockets\" (early form of electricity). From there we were constantly refining our tools and gaining knowledge, we got to make better and better sprockets and chains, we automated pushing the pedal (e.g. engine rotated by steam from boiling water) and rest is history. P.S. I am actually not english native and learned a lot of bike parts names :)" ], "score": [ 10243, 577, 78, 53, 19, 13, 7, 5, 4, 4 ], "text_urls": [ [], [], [], [], [], [], [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjdjn98", "gjf4456" ], "text": [ "URL_0 It’s called a “bulbous bow” and it reduces drag on the ship moving water. It increases fuel efficiency, speed, and the ship’s range.", "Since people who seem to know about cargo tankers are around, an uncle of mine worked in an adjacent job and told me about how cargo ships and cruise ships typically run on diesel fuel in port and in non international waters to adhere to pollution laws. However as soon as they get out to sea they switch to a very dirty-burning byproduct of diesel fuel production. Is there any truth to this or was he yanking my leg?" ], "score": [ 28, 4 ], "text_urls": [ [ "https://en.m.wikipedia.org/wiki/Bulbous_bow" ], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjdw9s9", "gjdwev1", "gje122w", "gjep8f1" ], "text": [ "The simplest and most common design has a master key that’s longer than all the others, and hits a second set of tumblers further back that the others can’t reach.", "There are lock and key combinations that can be designed with accommodating a master key. In college I shared an apartment with three other guys. We each had a key that could unlock our own rooms (but not each others). But all four keys worked on the front door. I think a good visual is a venn diagram - each key has a common design in it that unlocks the front door but enough variation in each to also only work on one specific room lock. A master key is the opposite of that - a single key pattern and a set of locks designed to be opened by that single pattern - but also take unique keys. I think someone else might be able to do a better job though, this is my attempt.", "If you look at any one of your keys and look at the different depths, imagine that for each one of those depths, there are 2 pins in a lock. The top pin and the bottom pin meet up. Where they meet up is called the sheer line. The bottom pin has different lengths to accommodate the different depths on your key. With a master key, for any number of those pins, you will have 2 or more of those bottom pins. Let's say the first position in all of the locks have 2 bottom pins. All the other pins are the same. With this, there are 2 keys that will work on that lock. When you put your key in, the sheer line is met. When the master key is used, a different sheer line is met since that key is moving up or down just enough for that 2nd pin to be in its proper place. Does that help? The link below shows what I am describing. [ URL_0 ]( URL_1 )", "An early example of a master key is a skeleton key that was used to open warded locks. Warded locks are the ones that have the medieval looking keys and the work by having a bunch of obstacles in the way between the keyway and the latch that opens the lock. Keys had those funny shapes so they would be able to bypass the obstacles for their own lock but not for other locks. Skeleton keys were called that because they had very few features and so could easily bypass most of the obstacles and hit the lever for many locks. Modern pin locks work by having a row of two pins stacked in a column into the keyway that block the core form turning unless they are lifted to a specific height by the key. You can make locks that can be opened by two different keys by adding another pin to the stack so that there are two different heights that the pin can be lifted and allow the core to turn, one for each key." ], "score": [ 28, 25, 7, 5 ], "text_urls": [ [], [], [ "https://i.ytimg.com/vi/8U6rdI\\_uG2c/maxresdefault.jpg", "https://i.ytimg.com/vi/8U6rdI_uG2c/maxresdefault.jpg" ], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjf760a", "gjf6ovm" ], "text": [ "Put diesel instead of gas in it. Or gas instead of diesel. Common rookie mistake, happens alot more often then people would believe", "URL_0 But seriously, it depends on what this generator is generating. What we think of as a generator, is a small engine, like a lawnmower engine, connected to a AC generator. There are large generators also, like the kind on Hoover Dam, but since there are no waterfalls or dams in outer space, I don't think that's relevant. So you need to tell us what sort of mechanical motion is being translated into what sort of energy? That's the essense of a generator. But without knowing what the parameters are, there isn't any way we can tell you what would fail on it." ], "score": [ 3, 3 ], "text_urls": [ [], [ "https://www.technobabble.biz/" ] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjfia9p", "gjfikkm" ], "text": [ "The ISS is in a relatively low orbit that’s not that good for most satellites, so many of them are a complete non issue. For the rest...planning. Orbits are *extremely* predictable. Space agencies track everything and identify any potential conflicts really far in advance. When you can see it coming days or weeks or months away, it only takes a *tiny* correction to make sure things stay apart. Everything larger than a few inches is tracked by radar all the time. It’s not satellites you worry about, it’s tiny space junk too small to track that’s a more realistic threat.", "2,800 may sound like a large number, but it's not when compared to the size of the Earth and the space above it. Think of how many planes there are each day flying through the sky, none of them hitting each other. \\[Not literally all, there are accidents with the majority human error\\] In the context of space, the satellite does not take up a lot of room. Additionally, you have to consider they are not all on the same plane. \\[You can think of plane as how many miles they are from the Earth, along with the path of their orbit\\] The ISS has a static, and well known, orbit. When satellites are launched they are released in such a way that their orbit does not collide with the ISS orbit, similar to a plane setting a course so that it does not collide with another plane." ], "score": [ 17, 4 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjgvokx", "gjgvxh0", "gjgxfjq", "gjgyyqm", "gjgxww4" ], "text": [ "It takes a lot of energy to create steam and power something. It's a lot easier to just burn gasoline and let that heat push some pistons and move things around. Back in the early days of atomic power there was a craze to put atomic energy in everything and they did play around with the idea of a nuclear-powered car but it's not reasonable for a lot of reasons.", "What are you going to use to power it? wood, coal, etc URL_0 They are low power and not terribly practical. The wiki is a good read.", "They can and they did. But heavy, cumbersome engines (of the time) doomed it. Generally the problem is energy density - gasoline engines develop much more energy/kg of fuel. (other than perhaps nuclear - but then there is the safety and shielding and risk of releasing pollution etc) With the current ICE engine, combustion is translated directly to motion rather than going through the step of heating an intermediate fluid.", "It's possible to run a car on steam. Some of the earliest cars were in fact steam powered. But steam has some disadvantages: - If it's an open system (the steam just gets exhausted to the air), that means that in addition to fuel, you have to haul around water, which is of course very heavy. And you have to make sure you don't run out of water OR fuel. - If it's a closed system (the steam gets recycled), that means that you need to have a heat exchanger to condense the steam so that it can be recycled. This removes the \"water as fuel\" problem, but that heat exchanger is expensive and heavy, and so is the pump to get the water back to the engine, and the necessary tubing, and so on. - Regardless of whether your system is closed or open, you need to heat the steam as a working fluid. That means that in addition to having a combustion chamber where the energy is being released from the fuel, you have to pass water through the chamber. This heat exchanger is, again, heavy and expensive. ___ The reason internal combustion engines became the universal small engines is that instead of using water as the working fluid, they use air. That means they don't have to carry around heavy water. Instead, they can just suck in air from the surroundings and use that - which you would need to do for a steam engine anyway! Basically, the advantages of steam engines are that they can be more efficient than internal combustion engines, and they can effectively be scaled up to massive plants. This means they're useful for large applications where weight doesn't matter much, like power plants, ships, and to a lesser extent trains. (They've been obsolete in trains for a long time, but they survived in trains for decades after they disappeared as car engines.) For anything where weight is important, the significant weight penalty associated with having to circulate water is a huge problem.", "> I believe nuclear power plants essentially work by generating steam *Every* power plant that involves some form of heat source - be it nuclear, coal or geothermal - uses steam turbines to turn that heat into electric energy." ], "score": [ 9, 8, 8, 6, 3 ], "text_urls": [ [], [ "https://en.wikipedia.org/wiki/Steam_car" ], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjgufvr" ], "text": [ "You know the roundabouts they have at the park? Where you can jump on and the other kids can push you round? Well imagine a load of kids all jump on to one side, and as the roundabout spins it doesn't work quite right any more and creaks and wobbles a bit as the other kids push it round. In a smart watch there's one of these but it's really tiny. That wobbling of the roundabout is felt as a vibration." ], "score": [ 22 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjjhx9m" ], "text": [ "Most of the energy use in a dishwasher is heating the water, not pumping it. Eco mode works by heating a smaller amount of water to a lower temperature, but gets the same cleaning by pumping that water round more times. So, it definitely uses less energy." ], "score": [ 14 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjjputd", "gjjqe9w" ], "text": [ "The gas companies make claims that the additives they put in it do various things to make your engine last longer but it's mostly bullshit. Higher octane gasoline has a higher self-detonation point, meaning the atomized (mist) gas and air mixture can withstand more compression before it lights itself on fire. If your car manual says you need higher octane gas, then you absolutely should use it, but if not then you're wasting your money. It isn't more powerful or efficient than the lower octane stuff. If your car does need higher octane gas and you don't use it, the fuel and air mixture will pre-ignite on its own which is also called \"pinging\" because you will hear such a sound coming from the engine. That pre-ignition can actually cause havoc on your pistons; actually melting them a little bit at a time.", "The grades of gas are **octane, not quality**. Octane is a measure of how much the gasoline can resist being compressed with air before it self-detonates. If you have a high performance car that needs the premium gas with high octane then if you don't use it the gas will detonate too early, causing something called \"knocking\" and possibly damaging the engine. If your car can run on normal gas (as most do) then all the higher octane gas does is cost more. You are just burning money pointlessly. It doesn't increase milage. It doesn't keep your engine clean. All it does is keep the fuel from exploding too soon if your car runs at higher compression where it needs it. If you can run regular without your engine sounding like there is a hammer inside it then you don't ever need the higher grade." ], "score": [ 3, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjk93ia" ], "text": [ "It was used in the Second World War to weaken the enemy's morale and scare them (you knew the bombs were coming but by the time you heard them it was too late to get to cove, it was basically a way of saying \"We are coming and you're going to die and there's nothing you can do about it\"). Same goal as with the sirens (AKA Jericho trumpets) found on the German Stuka dive bomber." ], "score": [ 9 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjo9ora" ], "text": [ "Engine sound is a product of the engine moving. 1000 explosions per minute sounds different from 2000 or 3000, and bigger or smaller explosions also change the sound. Some quieter newer cars *may* have speakers in them." ], "score": [ 5 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjoyim0", "gjp08l6" ], "text": [ "I worked at a seafood plant years ago, and its a HUGE process. Special door blowers create outgoing air that keeps bugs from flying in, countless mouse traps that are checked daily, special UV light systems to get whatever stray bugs that come in, and facilities that are more like hospital clean rooms than factories. It takes a team of people, usually a Sanitation Department and FDA trained supervisors, working 24/7 to keep the place clean and pest free", "Peanut butter is one of the most controlled foods in the FDA list; an average of one or more rodent hairs and 30 (or so) insect fragments are allowed for every 100 grams, which is 3.5 ounces." ], "score": [ 22, 8 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjq294w" ], "text": [ "Viscosity is how thick a liquid is. Water has fairly low viscosity, oil's is higher, honey and molasses are higher yet. It matters if you're designing a pump, or trying to move fluid through hoses or pipes. Viscous liquid takes more power to move, and it won't move as fast. Are you old enough to remember glass ketchup bottles? Viscosity. :)" ], "score": [ 10 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjrmv9e", "gjrmvx2", "gjrn484" ], "text": [ "A lot of it has to do with geography and climate. In the sunny desert you can build really nice, big solar farms that are gonna capture a lot of light for energy. But there aren't too many viable places to build dams. Wind might be able to produce more power per dollar invested into the infrastructure but you need a place that's gonna be gusty enough to make it worth it.", "The most cost efficient method will depend on where you are. Some places get tons and tons of wind. And some get almost none at all. Or some places get no sun, etc. It's not like fossil fuels where you can ship the fuel in. Renewables work by extracting energy that's already there. If the energy isn't there in the first place it wont be cost effective.", "As you guessed, it's not that simple. The most efficient/cost-effective option changes based on a huge number of factors. In general, they \\*do\\* use the most efficient option for a particular site but that option varies by site and jurisdiction. Having many different forms actually increases the chance of having one that works for any particular situation and provides a better global optimum than having only one technology. Wind is great...if you're in an area with high wind and lots of open space and relatively flat ground. Hydro is great...if you're in a place with sufficient rainfall and geography that can capture it before it gets back to sea level. Solar is great...if you're in a place with lots of sunlight. Geothermal is great...if you're somewhere that the crust is relatively hot (unusually high proximity to magma). Tidal is great...if you're near the ocean and the the right coastal geography to provide large enough tide swings to capture. Biomass is great...if you live in an area that has enough excess agricultural capacity to grow the materials without screwing up your food supply chain. It's the same reason we have coal, natural gas, nuclear, and diesel power plants. Those were usually the \"optimal\" (at least at the time they were built) for the location/requirements/laws in place in that area, but that doesn't mean everyone uses the same tech. Edit: it's not always obvious, but transmitting power long distances is relatively inefficient...if it weren't, we'd indeed pick just a few technologies, build the plants where that made sense, then ship the power everywhere. But power generation is inherently local." ], "score": [ 10, 5, 3 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjt2sfz", "gjtbm1e" ], "text": [ "Automatic weapons are only banned for ownership by private citizens. Defense contractors design, engineer, and produce weapons for the military.", "> Current US policy states: \"Autonomous … weapons systems shall be designed to allow commanders and operators to exercise appropriate levels of human judgment over the use of force.\"[22] However, the policy requires that autonomous weapon systems that kill people or use kinetic force, selecting and engaging targets without further human intervention, be certified as compliant with \"appropriate levels\" and other standards, not that such weapon systems cannot meet these standards and are therefore forbidden.[23] \"Semi-autonomous\" hunter-killers that autonomously identify and attack targets do not even require certification.[23] Deputy Defense Secretary Robert Work said in 2016 that the Defense Department would \"not delegate lethal authority to a machine to make a decision\", but might need to reconsider this since \"authoritarian regimes\" may do so. -Wikipedia The long and short of it is that automated weapons are not banned. So long as it is certified and has some degree of human control, it is considered sufficient. In the case of the Phalanx, it is fairly clear that shooting down missiles and torpedoes is not lethal force (unless they bring back manned torpedoes or somebody takes the f-104's nickname too literally), and these are the only things that such a device may be asked to do without some human's affirmation." ], "score": [ 3, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjvue4p", "gjvy7qz", "gjvxjuj", "gjvvemr" ], "text": [ "Space is indeed that empty. Sometimes you get hit, and crews have kits for patching holes, but unmanned spacecraft are just engineered to \"take a licking\".", "> are the odds of encountering some object so low that we basically decide to ignore it? Yep", "For long duration flights like the ISS we cover it in [Whipple Shields]( URL_0 ) which are specifically meant to absorb small ultra fast particles. If something makes it through it will at least be greatly slowed and the crew will be able to patch the hole. But whipple shields are heavy and weight is critical in space, so a lot of it is knowing that your path is relatively clear and hoping that it is completely clear. There is very very little stuff in interplanetary space so the biggest risks are as the probe is getting away from Earth. For stuff hanging out around Earth, we have tracking on most big pieces of debris and satellites in orbit. All satellites have some movement capability so if something big is coming they will try to get out of the way. The big important satellites live up in Geostationary orbit where everything is very well regulated and everything is moving in the exact same orbit so theres no collision risk. Down in the Low orbits most big chunks will slow down and burn up in the atmosphere pretty quickly. Basically you should build your spaceship to handle collisions with things that are in the millimeter range, they're the most prevelant but also the most survivable. You should build your spacecraft to dodge anything in the meter range, but if something 5cm across sneaks up on you at high speed there really isn't anything a spacecraft can do to survive that, but luckily there aren't a lot of things in that range hanging out in orbit or deep space for now.", "Space isn't just empty, its BEYOND vast. There's just lots of distance with not a whole lot between." ], "score": [ 16, 11, 6, 5 ], "text_urls": [ [], [], [ "https://en.wikipedia.org/wiki/Whipple_shield" ], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjwhoy8", "gjwhsqw" ], "text": [ "Potentially for reloading. Since the guns/shells are so massive, the crew would be quickly worn out after a few shots. They solved this by using powered rammers and loading mechanisms, which could lift the shells and propellant from the magazines below, then ram them into the gun breech. This would be easiest if the gun were level, so the rammer doesn’t have to push upward into the breech and the risk of stuff falling back out would be minimal/nonexistent. So the crew would be trained to fire, drop the gun, reload, raise the gun back to it’s proper elevation/angle, and fire again. See the animation: URL_0", "A lot of early war battleships could not reload the guns when it was tilted upwards at a high angle. They'd fire the round and then drop the barrel so the reloading equipment could ram the next shell and powder charge in, tilt back up, and fire again. Later designs would do their best to remove this requirement so the guns could stay trained on the target and not waste time going up and down. This was still a big step up from much earlier ones that had to lower all the way to reload and some weird turret designs that required facing a certain direction to get more ammo up into the turret The equipment required to handle shells that weigh over a thousand pounds is going to be big, and making a bigger turret to accommodate more flexible reloading equipment could make the ship much heavier than allowed, treaty battleships were already crappy compromises" ], "score": [ 14, 5 ], "text_urls": [ [ "http://en.wikipedia.org/wiki/Magazine_%28artillery%29#Naval_magazines" ], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjwv0r5", "gjwwzbo", "gjx45iv" ], "text": [ "Most buildings are built to last decades. Regular inspections occur, and if problems are found, they'll start repairing. How they'd do it is no less complicated then when the building was first being constructed. If the problem found is major then they'd (possibly) close the street and close the building. If the problem can't be fixed without knocking the whole building down then they'd knock the whole building down.", "There's solutions. Not applicable specifically to skyscrapers, but as an example residential homes if you have to repair a load bearing wall you tack on temporary ribs in the attic to redistribute that weight while you repair the damaged area. Once the repair is finished you remove the temporary bits and the repaired section takes the load again. The design of the structure is the first question to be asked. That will determine options.", "I worked in this sector! Pretty much every city has a law on its books requiring that building facades (the exteriors) of buildings over a certain height have to be inspected every so many years, 5 is a common requirement but it changes form area to area depending on its exact laws. Building owners will then hire engineering firms to come and inspect their buildings using one of or a mix of these main tactics. 1. Swing stages (those big scaffolds on the wires that you see go up and down the sides of buildings that window washers sometimes use. 2. Rope Access (which is essentially Rappelling, like you would down the side of a mountain (or like those window washers who dress up as spider man use). 3. Drone camera footage, this one is new and not super common yet, and typically done in tandem with one of the other two methods, but used to see hard to reach spaces). These inspections take in everything about the exterior, from cracks in bricks/mortar, Rusted metal joints or fasteners, missing chunks of concrete, dried out sealant, anything and everything. Those inspections then file a report deeming the building Safe or Unsafe, with a list of things that should be maintained or repaired. And in many cases those repairs are done the same way the inspections are. With workmen lowering down the side of the building on a swing stage to work on whatever needs to be done. Typically, these repairs are smaller, nothing major or catastrophic, because they get inspected so often. Buildings are built to last and then close to constantly checked up on to nip and problems in the bud before they turn into major problems. And for high traffic areas it can depend on what’s gotta be done. Some minor sealant work or grout/mortar work can be done without even shutting the whole side walk below down, maybe installing some safety netting or those scaffolding tunnels you walk under some times to protect anyone underneath on the slim chance anything falls. But if some major work needs to be done, especially work on something deemed to be a hazard to public safety, then the whole side walk, road, or whatever, can get shut down. But typically this doesn’t need to happen. Tl:dr, not every dude you see repelling down the side of a building or on one of those hanging window washer stages is a window washer, many are engineers/workers inspecting the building and/or doing repairs, all while you walk underneath them unknowingly." ], "score": [ 4, 4, 3 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjxnvno", "gjy0ib3", "gjy9whc", "gjy32t4" ], "text": [ "In both cases the propeller is actually more efficient when mounted on the rear. This is because the inlet cone on a propeller is much wider then the exaust cone so the hull of the craft is not so much in the way. However the problem that aircraft face is the issue of weight distribution. For stability reasons you need the weight of a craft in the front of the drag. The best example of this is an arrow or a dart which is very stable because it have a heavy point in one end and a tail for stability in the back. Airplanes are designed with the same principle. But in order to do this they need the heavy engines far in the front. Aircraft that use a pusher propeller therefore have to run a long prop shaft through the entire length of the tail of the aircraft. Some boats does have a very similar configuration but because they do not have to fly they usually have much smaller engines and propellers compared to the size of their ship. So they can easily get away with running a small propeller shaft along the keel of the ship to a center mounted engine. There is also another reason which is why even aircraft with wing mounted engines usually have the propellers in front of the wings. It has to do with low speed control. A big issue with low speed flying is that you do not get enough airflow over the control surfaces to be able to control the aircraft. One solution is to put the control surfaces in the blast of the propellers which gives them more airspeed. And because there are control surfaces on the wings you therefore need to put the propellers in front of the wings. Ships do the same thing but with a slightly different configuration. They put the rudder behind the propeller but the rest of the ship is still in front of it. If you look at some more extreme aircraft designs you do sometimes find this with pusher propellers as well. But cutting out parts of the wing or hull of the aircraft in order to place the propeller in front of the airfoils but behind the rest of the structure is often counter productive.", "FYI, it's not totally unheard of to have an airplane with propeller in the rear - see the Icon A5 for a modern example - [ URL_0 ]( URL_0 )", "I haven't seen it mentioned yet... To lift the nose up for takeoff, the tail has to be lowered very close to the ground. That greatly limits the size of the propeller you can mount behind the main landing gear.", "This is how I would explain to a 5yo. It's a speed problem. Things pulled from the front can go faster without falling over and things pushed from behind are more likely to fall over when moving quickly. Because a plane is a lot faster than a boat it needs the puller in front and a boat is a lot slower so it gets help turning when the pusher is at the back. I skipped a lot of other factors for the sake of getting to the cookies and milk faster." ], "score": [ 484, 25, 20, 9 ], "text_urls": [ [], [ "https://www.iconaircraft.com/" ], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjxqqy4", "gjxqjlc" ], "text": [ "Copper is not the best conductor for electricity, but it is a very good one, and its abundant in the Earth's crust, and relatively easy to produce, which makes it cheap. So the answer is actually quite simple: it's the most cost-efficient material.", "Simply put, we use copper for electric (power) and electronic (data) cables essentially because copper is a very conductive metal that offers high performance, can be bent out of shape without breaking and is rather inexpensive compared to other metals that are equally or more conductive. Nowadays, copper has become rather expensive due to demand for data applications and some low-end, cheap-ass cable manufacturers use poor quality alternatives, such as copper-coated aluminum, and sometimes even just plain aluminium, for some types of cable, namely network cable. Most of these poor quality cables come from China." ], "score": [ 7, 5 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gjywo0q", "gjyxa66" ], "text": [ "It's caused by the torque of the rotaing mass of the engine. Even when the transmission isn't engaged, the flywheel behind the engine is still spinning. Most automotive engine flywheels rotate (as viewed from the flywheel) counterclockwise - left. According to Newton's law, the engine and everything it's attached to will want to rotate in the opposite direction- right.", "“For every action, there is an equal and opposite reaction.” When the motor spins in one direction, the rest of the car feels a force\\* in the opposite direction. \\*(technically a torque; it’s like force, but in a rotational frame instead of linear.) It’s like when a motorcycle accelerates too fast and pulls a wheelie. The rear wheel is spinning “forward”; the rest of the bike gets spun the other way. If this torque is strong enough to overcome the force of gravity, the front wheel lifts up off the ground. In your car’s engine, it’s the same thing, except the spinning motion is sideways, so your car lurches to the (other) side instead of to the back." ], "score": [ 9, 4 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk0701z", "gk07d21" ], "text": [ "If it takes days to recharge, either your device's charging system is broken, or the batteries have reached the end of their useful lifetime and need to be replaced. Should only take a couple hours max to fully recharge.", "I’d guess because 1 ) the toothbrush is inductive charging, which is much slower and 2) those larger devices are significantly more expensive, so one way the toothbrush companies cut costs is to use much slower battery technology." ], "score": [ 9, 6 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk0c4sr", "gk0c09w", "gk0a39s" ], "text": [ "Hospitals are designed so that in the event of a fire, doors will close and will prevent the fire from spreading until firefighters can deal with it. The doors are rated, usually by number of hours, for how long they will hold back a fire on the other side.", "Good fire suppression systems to stop the source of the fire. Extremely well insulated fire proofing materials to slow the spread of a fire to give more time for the evacuation. Very regular fire exit points, including surgery rooms. I imagine if there is a surgery happening and a serious fire occurs, the surgeon will have to decide if he has time to stabilise the patient and evacuate, if not then unfortunately there's not much you can do. This would be very rare however. For other patients, there will be procedures in place to get them out asap and that procedure will be very different in different hospitals. Edit: spelling", "I’ve actually had to do this. We wrapped people in damp sheets and carried/dragged them (gently) downstairs. edit: grammar. Further edit: 1983, only one fire wall." ], "score": [ 14, 8, 5 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk0emp7", "gk0e0er", "gk0gqct", "gk0dy1u" ], "text": [ "It's more about the power that a vehicle can deliver somewhere between its top speed and the speed limit. If you test drive a car that accelerates poorly from a merging interstate lane, you're going to drop it pretty quick for a model that can jump to attention when you want it too. The fact that it can top out at a high speed isnt the design intent, rather a byproduct.", "Vehicles designed for commercial use can have speed limiters turned on in the ECM so the truck or van won’t go past a certain limit. However the gauge on your car goes up to 140 doesn’t mean the car can physically or safely go that fast. Even on a closed track. It’s mostly for psychological reasons and so manufacturers can reuse gauges.", "It has to do with gear ratios. You would use the highest gear at highway speeds to keep the engine rpm's low for fuel efficiency. You would not want your engine revving at 6,000 rpm for the car to go 75 mph. This is a relatively normal highway speed. They make it closer to 2000 rpm by adding a larger gear. This way, the engine runs at a more efficient point of the power/torque curve when you are at the expected speeds, but the car could go faster than it is probably safe to operate at rpm's higher than they would want the engine running at over a length of time. As others pointed out, the numbers on the speedometer mean nothing; I have a 5.0 Mustang where the speedo goes only to 85 mph. I have had it faster, the needle just keeps going", "I bought the whole speedometer I’m going to use the whole speedometer. But really. Many vehicles do govern out at a speed. Fords for a long time were 112 I believe. I owned a few. My Acura seems to get to 120 no issue. I like to open them up every now and then when it’s safe. They want to keep their customer base happy. And people would just disable it anyway." ], "score": [ 17, 8, 4, 3 ], "text_urls": [ [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk0i0p0", "gk0gwlh" ], "text": [ "As a left hander f the people who dont think about us. Left hander tools are so expensive. I understand that majority is right handers but why cant they make it universal? Can openers are made specifically for right hands. And scissors. I adapted but my right hand is weaker and cramps more. Also I'm short too.", "I've honestly never seen a hand-specific peeler, but scissors and pruners both require squeezing the hand. Having a stronger or \"dominant\" hand comes into play with repeating that action a million times, so having tools designed to over the most comfort to a given hand will proven useful." ], "score": [ 4, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk0qq0i", "gk0v2po" ], "text": [ "Zero or close to zero emissions, as opposed to mostly everything else that runs on fossil fuels. There is some speculation at how much better they will be in the long run though.", "> Why are electric cars better for the environment? The short answer: Because they are more efficient than gas cars. The long answer: Because the large majority of any car's environmental impact is incurred in operations rather than manufacturing, and EVs have much higher operational efficiency than gas cars - so much so, in fact, that they more than offset any increase in manufacturing impact incurred by the batteries." ], "score": [ 7, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk13rpv", "gk14s6k", "gk14ln2", "gk13niu" ], "text": [ "It does a couple of things. First, the vibration isn't just vibration. The impact driver exerts very high torque on each impact, but it is much easier to control because it is broken up. If you were to apply the same static force, like from a drill, you would need much better leverage and risk shearing the screw. The second thing that happens is actually due to vibration. When a bolt is stuck, like a lug nut on a car, the vibration helps break corrosion or even cold welding on the nut/bolt. Drill's were never really meant to install screws and bolts, they work best when drilling holes. Impact drivers work great for removing/installing nuts, bolts, screws, etc... Screw guns work better than impact drivers for screws in wood and drywall, but are pretty useless outside of that. There are probably other principals at work, but those would be the main two.", "A regular drill applies static rotational force to the shaft and, consequently, the bit. In other words, it exerts a constant pressure to rotate the chuck. An impact driver senses when you need additional torque and creates rotational impact force with a spring, hammer, and anvil. As the motor turns the shaft, the spring compresses and then releases forcefully, driving the hammer against the anvil. This action happens rapidly – more than 50 times every second – and creates a much larger force than a drill can muster. Here’s a way to think about it: using a drill is like setting your hands against an object and pushing while using an impact driver is like punching it. The same muscles create both forces, but the punch delivers much greater force. A punch also only impacts the surface for a brief moment while you can engage a push much longer. ust like a punch, the impact mechanism creates a more violent action. That’s why you see few Pros using impact drill bits and spade bits. It’ll get the job done, but it’s not nearly as smooth of an experience. On the other hand, that violence is perfect for driving screws faster than a drill can. The speed of the hammer/anvil impact combined with the additional force gives you the ability to drive longer and larger diameter screws than you can expect a drill to tackle. The icing on the cake is that impact drivers are typically smaller, lighter, and able to get into tighter spaces. They also won’t wrench violently in a bind-up like a high-torque drill. If that all sounds, well, *impactful,* you’re not alone – impact drivers are among the most popular cordless tools on the job site. [How an Impact Driver Works: Training the Apprentice | Pro Tool Reviews]( URL_0 .)", "Imagine you are removing the lugnut from a tire with a cross-type tire-iron. You turn it by applying constant pressure with your arms and try to loosen the nut. Compare that with turning it with your arms while your buddy smacks it with a hammer in the direction you are turning.", "They are capable of exerting significantly more torque. Imagine trying to turn a bolt with a wrench. Now imagine hitting the wrench with a hammer. Your arm never exerts any more force, but the percussion of the hammer allows a higher peak torque to be applied, increasing the torque applied to turn the bolt." ], "score": [ 17, 6, 3, 3 ], "text_urls": [ [], [ "https://www.protoolreviews.com/news/how-an-impact-driver-works-training-the-apprentice/34862/#:~:text=An%20impact%20driver%20senses%20when,the%20hammer%20against%20the%20anvil" ], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk2id0d", "gk2d5ji" ], "text": [ "A lot of the comments below are addressing the whole electric car ecosystem, but you appear to be just asking about the engines. The simple answer is that a gas engine is a thermodynamic engine (works based on heat) and an electric motor isn't. All thermodynamic engines (gas engines, diesels, jet turbines, coal boilers, etc.) have an inherent physical efficiency limit related to their hottest high temperature and their lowest cold temperature. The gas engine in your car uses the atmosphere as the \"cold\" side, so that can never be lower than about -40C, and the high temperature limit is pinned down by the materials you make the engine from and the cooling system. This means there's an upper physical limit on how efficient the engine can ever be, and it's not that high...typically 30-40%, far lower in practice. Electric motors use a whole different kind of physics, they convert electrical energy directly to mechanical energy without any messing about in the middle with heat. This means the thermodynamic efficiency limits don't apply. Good electric motors can be well over 95% efficient. \\*How you get the energy to the engine\\*, and how that gets to the wheels, varies wildly, and is what most of the other comments are about, but the engines themselves are totally different and they have correspondingly different efficiency limits.", "Comparing efficiency doesn't really make sense here. The advantage of electric cars is that they can make use of electricity which is at least partly generated from renewable or non-polluting sources. Additionally any fossil fuels that are burned to generate that electricity are burnt in power stations which have decent pollution controls and are not right in the middle of built up areas, reducing airborne pollution where lots of people are living and walking. Does that answer your question?" ], "score": [ 11, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk30rsz", "gk317gt" ], "text": [ "The Neutral line should be at 0V or very very close. In house wiring the neutral wire is tied to Earth ground back at the panel and both are tied to a long metal grounded rod. While current does flow down the Neutral wire, you could not power something by connecting it between Neutral and Ground because Neutral is just the reference/return, its not being pushed/pulled. 'higher voltage line' and 'lower voltage line' gets confusing once you start looking at real wiring. A house gets 2 hot lines (Phase A and Phase B) which are both the same voltage relative to Neutral but 2x the voltage relative to each other. Neutral is really a neutral middle point between these two rather than being higher/lower voltage (you could say phase B is the negative of the phase A voltage which would make it lower(kinda)) Neutral is a far more accurate term for the line than \"lower voltage line\", especially if you get into a commercial setup with 277V hots and 120V hots.", "No, AC is alternating, and the voltage of neutral is higher than hot 1/2 the time. The name is to distinguish it from the ground, for ground fault protection. The \"hot\" is actively protected, and a fuse/breaker trips if you draw too much current from it." ], "score": [ 15, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk44jks", "gk4429s" ], "text": [ "Kevlar is a polymer (very long thin molecule), like many plastics, that can be made into fibers, like nylon or polyester. However, it's somewhat unique in having extremely high bonding forces between adjacent molecules. This makes it really really tough and strong compared to other polymers. The combination of relatively low density and relatively high strength gives it \\*really\\* high strength-to-weight ratio (better than steel), but it's still a soft polymer so it's not brittle like glass, carbon, ceramic, or very high strength steels. This makes it unusually good at absorbing energy, very difficult to cut, and you've basically got a lightweight steel that you can weave in rope, fabric, etc.", "From what I've gathered it's a bunch of layers that are stacked on top of each other with an adhesive to keep them together. Essentially when the bullet penetrates the layers they twist around the bullet like silk does when an arrow head strikes it. Pretty cool stuff actually. Don't take my word for it though. #usernamechecksout" ], "score": [ 11, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk7yxce", "gk7zw3m" ], "text": [ "Those are electromagnets. They are magnetic when current is passed through the coils and not when the power is turned off. (some residual magnetism but not nearly as much) URL_0 URL_1", "There are two kinds of magnets: permanent magnets (like fridge magnets) and electromagnets (like those security doors and scrapyard cranes). The difference is how its made. For permanent magnets, you expose a metal to a strong magnetic field while it is cooling from a high temperature. Each atom in a metal has its own magnetic field, and when you do this process, you line up those magnetic fields so they add together instead of cancelling each other out. This creates an object with a permanent, but fixed, magnetic field that will last so long as the object isn't destroyed. For electromagnets, you exploit the fact that a flowing electric current generates a magnetic field. In most solitary wires, this field is very weak. However, if you wrap these wires into a coil (called a solenoid), you get a much stronger magnetic field. If you then wrap the coil around a ferromagnetic core (i.e. a piece of metal that you could turn into a permanent magnet, even if it isn't one), you get a much stronger electromagnet. The key here is that the magnetic field only exists so long as the current is flowing, and what's more, the direction (north vs. south) depends on the direction the current is flowing around the coil of wire. You flip a switch, the magnet turns off. You flip the direction of the current and the magnet reverses polarity." ], "score": [ 8, 5 ], "text_urls": [ [ "https://sciencebob.com/make-an-electromagnet/", "https://youtu.be/x5MUtL_tSwE" ], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk840zl", "gk84lwx", "gk8z94w" ], "text": [ "The nuclear reaction itself causes the reactor to get hot. This heat goes into water in order to turn it into hot pressurized steam. That steam then goes into turbines to spin them and this rotation runs generators. This is where the electricity comes from. The issues of safety mostly comes from controlling that heat generation. The process will just keep running causing the reactor to get hotter and hotter if not controlled. Rods can be inserted into the reactor which absorb radiation which will slow down nuclear reaction and slow down heat production.", "Uranium (or less commonly plutonium) splits via controlled nuclear fission, generating lots of heat, and some radiation. We use the heat to boil water into steam. The steam spins a turbine, which spins the generator. Nuclear fission = splitting heavy atoms into two or more smaller ones. This releases a lot of kinetic energy (heat), and sometimes radiation and neutrons depending on which atoms are splitting how.", "Interestingly enough, the WAY most power plants, including nuclear, gas, coal, etc. produce electricity is the same. They heat water (generally until it forms steam) and that water turns a turbine. The way they generate heat, on the other hand, is different. Coal and gas is easy, They essentially burn it in an \"efficient\" (but not really at all efficient) combustion chamber. Obviously when you burn something, it creates heat. Nuclear power plants are slightly different. They don't burn anything, but it's still a chemical reaction that produces heat. Think of a handwarmer. It produces heat but it's not burning. So various chemical reactions can produce heat. It just so happens that the one that occurs inside of a nuclear power plant also produces heat. This heat is harvested in the same way as other power plants, by running water near it and the water heats up, etc. etc. etc." ], "score": [ 7, 3, 3 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk84oip", "gk86bg3" ], "text": [ "So, to understand multi-viscosity oil (two numbers) you have to realize that the first number is how thin the oil is when cold, the 2nd number is when it's hot. When your engine is hot, it needs to be lubricated or things break. When cold, if the oil is thick, it's hard to get things moving. That being said, the weight of the oil depends on the size and performance of the engine. A small engine (like 2 liter) doesn't need 10w40 because it's small and not generating as much heat and friction. A large engine (5 liter) probably runs 10w40 because it will generate much more heat and friction. So it needs better lubrication. I have an old 5.3L car that I run 20w50 in. It's very thick oil. But it's a big old engine, so I want the extra protection.", "In short, viscosity... i.e. how well does the oil flow (and therefore lubricate) when its cold, and when the engine is running. The lower the number, the thinner it is and thus the better it flows at cold temperatures. Higher numbers are thicker and lubricate better at higher temperatures. When there's two numbers, the 2nd, after the W, is how well it flows when its hot i.e. the engine is running. The first describes how it would behave when its cold. So 10W30 say is good from about -20C to +30C... but outside of those ranges it wouldn't behave too well. Colder and it would be gummy and maybe your engine wouldn't start easily. Warmer and well, it would lubricate your engine too well, you'd get lots of issues. If you lived where it was super cold to moderate, say 20C or less most of the time, 0W20 might be for you. If you lived in Arizona, maybe 20W50 is for you." ], "score": [ 4, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk8iare", "gk8ii3h" ], "text": [ "The light that runs your car battery dead overnight would run down your AA batts in an hour. Things that are designed to run on batteries use much more efficient (and expensive) technologies. Car lights are designed for vibration resistance and long life, rather than electrical efficiency, because when the car motor is running there is a significant excess of available electrical power.", "Car batteries are designed to deliver a LOT of amps for a short amount of time to get your car started, and then to recharge off the power provided by the engine. They're not well optimized for delivering a trickle of electricity for many hours." ], "score": [ 18, 4 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gk97kkm" ], "text": [ "Axle construction and tank thickness can make a big difference. Also if it is a heavier car, they may only be able to carry so much before they risk the chance of breaking the couplers holding cars together." ], "score": [ 6 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkal4rk", "gkaljdu" ], "text": [ "The \"platform\" is essentially the floorplan and all the mechanical components of the car (the engine, suspension etc)--what would have been the chassis in old-style cars. Such a structure isn't rigid enough by itself to be a workable car, but once you build a body on top then it becomes one.", "“Platform” does not mean the unibody. It basically means everything *but* the unibody. The platform is the architecture of the car, in the engineering sense, not the aesthetic sense. Common platforms use the same arrangement of components, the same components when possible, and the same interfaces. Lego is a platform...individual Lego models are the individual cars. Platform design allows you to make a huge variety of end items using a much smaller set of parts and reuse a lot of engineering and design." ], "score": [ 6, 4 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkb0gtm", "gkb3eru", "gkb2ail" ], "text": [ "They aren't all like that, but the ones that are is typically because the driver is sitting further forward/higher in comparison to the steering gearbox than the driver in a car does. Fewer joints to adjust the angle of the steering wheel leads to better responsiveness and fewer parts to break.", "There's a few answers here... Having the steering wheel horizontal makes it easier to pull/push the wheels as needed. A bit of a fail-safe, if you have to muscle the wheel as well... but, that'd be pretty rough honestly. The seats help cushion the rider and can travel a good bit. If the steering wheel was more vertical, the driver would constantly hit the wheel with their knees and thighs potentially. The steering wheel has more leverage with a direct connection to the steering box. If they used universal joints to change the steering wheel position, it would make it harder to spend 8 hours driving it. Otherwise, it might very well be partially due to preconceived notions that a big rig should also have a big wheel. As I'm sure an engineer could design a reasonable steering box and steering wheel that would give an everyday feel... and likely be safer with a working air bag.", "For the types you are talking about, it helps the operator see better outside the vehicle, by raising their seating position and removing the wheel from their forward vision." ], "score": [ 19, 7, 4 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gke342l", "gke2u92", "gke3fjf", "gkeoe7t" ], "text": [ "> wouldn't it be straight up invincible because all the shells would straight up ricochet off it harmlessly? This assumes shells never come from odd angles you didn't plan for. The main issue for keeping tanks safe is being able to defend against various different armor piercing concepts that all need different approaches. Angles are most important for kinetic projectiles, but don't help much against HESH (high-explosive squash head) Also your flat pyramid design would likely be too wide to move through difficult terrain.", "You’ve been watching too many cartoons. Largely armor piercing rounds destroy whatever they contact. As an added bonus they’re normally hot enough to set the innards of whatever they hit on fire.", "If you look at tanks they do not have 90⁰ straight up and down angles. Tanks walls are already built to deflect rounds where they can. Also pyramids are cool looking.", "Hmm, interesting question. TLDR/ELI5 explanation: Too unergonomic, no space for anything. Would also be too wide/large to move and that would also make it highly vulnerable. Basically, would be nothing more than target practice for bombers. Only real way that this can be applied is something like the WWII Hetzer, or the Swedish Stridsvagn 103. Full explation: Its not the first time questions like these have been raised before but normally with sphere-shaped tanks, for example: the Kugelpanzer from WWII, a spherical, 1 man recon tank; or the idea of a 'Tumbleweed tank' from 1936 from some dude in Texas, probably after having too much to drink. While spheres are strong structures and apply the same logic to bounce and deflect shells (except for where it's flat facing the enemy), anything bigger than a 1 man tank would be downright silly due to ground contact, ergonomics, engine structure, etc. Too tall, easy to hit, hard to build, you get the idea. However, it doesn't mean that it was a totally bad idea. Spherical designs in tank turrets have been seen before, notably in Russian designs like the round IS turrets and especially in the Soviet MBT in 1961, the T-62. The closest thing to what you are thinking of that I can think of would be the Jagdpanzer 38 (Sd.Kfz. 138/2), more commonly known as the Hetzer. Enclosed in sloped armor, the Hetzer was a reliable tank for the Germans in WWII, easily being able to destroy Allied and Soviet tanks even at distance with its Pak 38 gun. Sloped armor made it difficult to destroy and its low profile made it hard to detect. However, it suffered to it's limited gun traverse, poor side armor, and limited ammunition storage due to it's small size. This would be a good example of the tank you're envisioning. However, back to your idea, with sides angled at 5 degrees, this tank would be comically large and wide. Dive bombing target practice, vulnerable to infantry, inmaneveurable, heavy, no space for crew, no space for anything really, you name it all. A molotov on this thing would make anyone unlucky enough to be inside this thing to bake like being in an oven. Also, at 5 degrees, any tank thats shooting at it from a slightly elevated position will easily penetrate its flat sides. The 5 degree angle idea just assumes that you are fighting at even ground at all times. To be more realistic, maybe a 30-40 degree angle would work, but still be comically large. If the top part of the pyramid were to be a turret, where would fit the turning mechanisms, the engine and everything else that goes into a tank? Note that the space in the tank would decrease since all the walls are angled in, leaving no room for crew or anything for that matter. Any larger angle would just forfeit the idea of angled armor, and forfeit whatever stealth the tank had as it's profile would be very tall and large, making it an easy target to hit. Tanks are shaped the way they are as we haven't found any better way to make them as of yet. The closest modern tank that takes some aspects of your idea would be the Swedish Stridsvagn 103, throwing away the idea of a turret and angling the entire front of the tank with the turret mounted in it. It mainly uses hydraulics to elevate the gun and it's low profile emphasized on survivability. However, it has never been in combat so we know not of it's effectiveness. Aside from the Hetzer, this is the only other real that the 'make the whole tank angled' I've seen that is somewhat feasible. Regards, a geek with too much time and a unrelated exam to prepare for." ], "score": [ 23, 11, 10, 5 ], "text_urls": [ [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkejpge", "gkfarh5" ], "text": [ "There is more to this question than just the actual physical reason for it. Light bulbs are probably the most prominent example of 'planned obsolescence', which means that they are designed to only last for a given amount of time. The reason for this, was that in the early days of the light bulb, companies were able to make light bulbs that could technically last for centuries. Some of those bulbs still exist and have been burning continuously for more than a century! However, if all light bulbs lasted that long, after the market had been saturated, nobody would ever need to buy new lamps. Thus, the companies who made lamps decided to jointly sign an agreement that they would all make their lightbulbs less resilient, so that they would eventually break after around 1000 hours. This pact is known as the 'Phoebus cartel', and included manufacturers like Philips, Osram and General Electric. However, this was the case for incandescent light bulbs. Other types of light bulbs may have different light spans. In general, the 'burning out' has to do with the wear on the internal parts that eventually break the circuitry in the lamp. The wires can corrode, they expand and shrink constantly because of the heat, and over time, these factors make it so that the parts become more and more 'brittle', and eventually, usually when turning a lamp on, they fail or break.", "Have you ever taken a piece of metal like a wire and bent it and then unbent it, and then re-bent it, back an forth, until the metal simply broke apart? The reason that happens is because of mechanical stress being placed on the metal. Even smaller stresses, if given enough repetitions and time can cause a similar failure. When you light an incandescent bulb you're heating a metal filament to thousands of degrees. Heat causes the metal to expand and when the light is switched off the metal cools and contracts, this repeatedly stresses the metal much like bending and unbending. The filament doesn't just fall in half from stress though. Instead it begins to fail at it's weakest part, but it can still form an electrical circuit. However this failing area starts to pull apart, forming a much thinner passage for the electricity to run through, which greatly increases it's resistance, which due to the flow of electricity causes it to heat up even more than the white hot temperature it was already at an WOOSH, the light bulb gets very bright for a moment and then burns through the filament and it goes out. This is why they tend to fail when turning on, not while they are already on, and why they get very bright at the moment of failure. For a few hundredths of a second, it's like you swapped their relatively dim, beefy, filaments, with a much thinner, brighter one that burns out instantly." ], "score": [ 14, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkf6zst", "gkfbgbm", "gkghq5u", "gkgah7u" ], "text": [ "Your car's heater is getting free heat from the engine, but that only works once the engine gets hot, which takes a few minutes. The space heater is taking energy from the power mains, which is faster to heat up, but you have to pay for it.", "The car heater works on the heat of the engine - it \"has to\" heat the entire radiator to a decent temperature first (if you try to suck the air from it too quickly, you will literally cool the engine even more which you don't want on a cold-start). The engine runs, heats the water, the water heats the air in your car. You can \\*get\\* electric heaters, etc. for the car, they are usually stupidly pathetic (12V, often limited to only 10A on a cigarette lighter socket, is 120W) or aren't something you can have running for more than a few minutes, when the engine has just started, or in cold conditions. Basically, you sacrifice your heat for the first minute or two of operation to keep the engine running smoothly in cold conditions, then when it has an excess of heat it's designed to give you that. And anything that sucked the power from the engine in those first few minutes will hinder a cold-start and will, also, take a huge drain and leave you with a flat battery if you use it for more than a couple of minutes. I used to have a Ford Mondeo (Fusion in the US, I believe). It used to have a coil-heater in the airvents. It could blow hot air immediately, but it was a draw on the battery, and even then it wouldn't kick in immediately. It was also notorious for failing and even starting fires. I have a newer Ford Mondeo. It does not have that. Manufacturers will tell you - the best way to warm up the car in cold conditions is to drive it normally, and not too much strain on it. Suffer that minute-or-two when you've just got in from the cold outside, and are now in a cold, but not windy, car. Because anything else will leave you with a flat battery, an engine that can't crank, or a fire hazard.", "This question makes me wonder if I’m supposed have the AC on when I have the knob turned to hot. Does the AC power the heater too or should I just leave it off as heat only comes from motor? I assume it needs to be off because I haven’t been able to find a difference.", "As others have said, the heater in your car pulls free heat away from the engine. It works like this: When you first start your car, the engine is cold. Inside your engine are pathways where engine coolant (water mixed with chemicals that are resistant to freezing) flow to keep your engine from getting too hot (overheating). The way it keeps your engine's temperature down is by cycling the engine coolant from your engine through the radiator and blowing air (by using a fan as well as forced air as you travel down the road) over the fins of the radiator. Actually, there is a device in your engine that delays this cycling of coolant in order to speed up the engine warming to normal operating temperature (about 165 - 180 F). This device is called a thermostat and it remains closed and blocks the flow of coolant into the engine until it reaches a certain temperature (or it would take even longer for the heat in your car to start working). To heat the air in your car, it has something called a heater core which is mounted somewhere under/behind your car's dash. This heater core is basically a smaller radiator. A fan in your car's ventilation system blows air over this heater core and into the passenger cabin. Until hot coolant flows into this heater core, you will not have any warm air coming from your car's vents. As a side note, it's easy to tell if your car's thermostat has broken in the open position. Your engine will take a very long time to reach normal operating temperature and your vehicle's heater will similarly take a very long time to start producing warm air. Additional side note, the heater core on my 1968 Plymouth Valiant popped one morning on the way to work and instantly dumped hot coolant into the passenger floorboard of my car while simultaneously seriously fogging every window in my car. I had to stick my head out the window to make it safely to the side of the road." ], "score": [ 232, 10, 4, 3 ], "text_urls": [ [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkhb6w3", "gkhb73i", "gkhb33c", "gkhijzh" ], "text": [ "We do. Ships are built with bulkheads and watertight compartments which let's them take damage in certain spots and stay afloat RMS Titanic is probably the most famous ship with good compartmentalization. It had 16 watertight compartments and could stay afloat if up to four were flooded, but damage to more than four results in too much weight and not enough buoyancy and then sinking. Warships had much more extensive compartmentalization because they were expected to have a good number flood during action. But in the end, some of your compartments will flood and you can't make useful unfloodable compartments, only unless ones filled with foam like on really small boats", "Ships *do* have many sealable compartments. The air won't exactly last indefinitely, and rescue won't come very fast. I'm not sure what exact stories you've been hearing, but I suspect that they're unique circumstances, like shipwrecks near shore.", "We do this, within limits. Most ships have compartments with watertight doors. Just sealed compartments is a huge waste of space.", "For ships to do their job, they need large clear areas that they can fill with cargo, clear areas where people can work, open spaces that people want to be in. For resistance against sinking, you want lots of tiny spaces all sealed off from each other, making it hard for people to work, claustrophobic spots where no one wants to be Balancing those two different needs is challenging." ], "score": [ 12, 6, 5, 3 ], "text_urls": [ [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkhu8ni", "gkhujwg", "gkhuuw8", "gkhv5u3" ], "text": [ "Nuclear power plants are just giant kettles. They use nuclear energy to boil water, and they run that steam past turbines which generate electricity when spun. The concrete towers you see are specially designed to remove the excess heat from the steam produced, so the water can be reused. Some large nuclear power plants can use up to 1 billion gallons of water a day, so it's important they recycle as much as they can.", "They are for cooling by convection. The hot pipes from the plant are in the base of the tower. The bottom of the tower is open, supported above the ground. The air inside heats and rises, pulling in cold air from around the tower base, cooling the pipes. The shape is to make the rising airflow as effective as possible while allowing for a huge, hollow construction. They're used on many power plants, not just nuclear.", "Those structures are called cooling towers. There are many shapes. But, the hyperbolic structure is preferred. At the bottom, the widening of the tower provides a large area for installation of fill to promote thin film evaporative cooling of the circulated water. As the water first evaporates and rises, the narrowing effect helps accelerate the laminar flow, and then as it widens out, contact between the heated air and atmospheric air supports turbulent mixing. They are superior in stability towards outside forces compared with \"straight\" buildings.", "They're the cooling towers the plant uses for the steam cycle the plant uses to produce power. Most plants have the water in the reactor at a very high pressure to keep it from boiling even heated up to several hundred degrees. That water is used as a heat source to boil a separate mass of water to make steam. The steam spins a turbine (effectively a big mechanical pinwheel) and then gets cooled by a third set of water so the condensed steam can be sent back to become steam again. That third set of water is what goes to the cooling tower. It sprays out of a huge network of sprinklers and some becomes steam. The shape of the tower acts like a chimney to direct steam and warm air up and drafting new, cooler air in at the bottom to cool off the rest of the water which falls into a pool before being sent back into the plant to condense more turbine steam. The cloud coming out at the top is simply that humid air venting out the top into the cooler outside air." ], "score": [ 20, 14, 5, 4 ], "text_urls": [ [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkkha8d", "gkk3zp1", "gkkqvht" ], "text": [ "1. \"burn down\" doesn't necessarily mean to be reduced to a pile of rubble. Even if all brick and concrete in a building remained intact, renovating a building where every bit of wiring, plumbing and interior decoration is busted, AND has water damage and toxic contamination from smoke will be more expensive than just rebuilding. 2. High temperatures weakens concrete. There's some water inside, which will boil and make the concrete pop off or at least lost strength.", "The brick is usually just a shell and is only good at holding weight vertically. It's quite weak in other ways. When the building burns all the insides start to crumble in ways that will fall against the brick wall pushing it over.", "Brick walls require the floor and roof levels to hold the walls in place, or else they’d have to be a lot thicker. If they lose this support they can become unstable. The process of the floors and roofs failing can also pull the walls down too - with floor members that are fixed into the walls they can drag the walls inward when the floors collapse, causing walls to fail. If you have metal floors (either steel beams or things called “bar joists”) the steel can expand during the fire and push the walls out. This is the primary failure mechanism for a lot of steel framed buildings that suffer catastrophic fire. A lot of components in brick buildings are also wood - for example in most older brick buildings you see theres a wood member above every window and door that supports a “triangle” of brick above it. When this burns the bricks above the window/door can collapse. If you have windows located above each other on each floor (common) this can lead to collapse of all the sections of walls above/below the first window to collapse. Further- the bricks are typically “fireproof” but mortar isn’t, unless you get fire specific mortar. The heat from a fire can basically turn the mortar to sand, while at the same time the walls are undergoing thermal expansion that makes them expand horizontally into each other, causing damage, and differential vertically (more on the inside face) tipping them over a bit." ], "score": [ 8, 5, 4 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkkou1f", "gkl0h42", "gkkott9", "gkkounf", "gkkx7so", "gkmsgth" ], "text": [ "That’s a p-trap. It is designed to hold water in the low part to prevent stinky and dangerous sewer gasses from coming up through the drain. So, yes, a straight pipe *would* drain better but the curved pipe drains well enough *and* it doesn’t stink.", "As others have said, it exists to prevent sewer gasses from flowing back up the pipe into your house. The P-trap is always filled with water so no gas can get past. I don't see anyone addressing how it works though. As in how it still drains. It's pretty simple. As long as the outlet side is lower than the intake side there's no problem. Don't think of it as water flowing back uphill. Just picture that 'U' part of the trap constantly filled with water. If you keep adding water it's going to fill up and 'overflow'. Because the outgoing side of the 'U' is lower than the bottom of your sink, it overflows on that side and goes down into the sewers. The P-trap is *always* full of water and when the faucet is running the trap is constantly overflowing. Just overflowing out the side that goes to the sewers. But in general, you are correct that you need to keep a downward slope. Drain pipe always needs a slope of 1 inch every 4 feet. That is still being done here overall. The P-trap only works because the outlet side is lower than the bottom of your sink; it's slope is actually quite a bit more than 1\" per 4', essentially", "The main reason those \"sink traps\" exist is so that there is always some water in the pipe. That blocks any sewage gasses from coming back up through the pipe, causing a potential health hazard, as the gasses can be quite noxious.", "It’s called a P Trap. In plumbing, a trap is a U-shaped portion of pipe designed to trap liquid or gas to prevent unwanted flow; most notably sewer gases from entering buildings while allowing waste materials to pass through.", "Why it's the shape it is has been covered well: some water stays to block the stink that would otherwise come out. If you've ever found an old toilet that's run totally dry and wondered why it smells worse than a freshly pooped-in one, this is essentially why. When the water's gone, sewer gas can finally escape. The other part of your question I haven't seen addressed. The short answer is pressure and how water behaves when it's touching other water. Picture a U-shaped tube you're filling with marbles. Eventually the marbles are gonna get pushed up and out the other end, right? That's your pressure. The behaviour of water that makes this even more effective is that water loves to \"stick\" to other water and pull it along. Think of a siphon-- if you've never seen one in action, it's a tube that can be basically any shape or length. It can look like a crazy straw, it can be straight, whatever you want. You place one end in one source of water, the other in another. The only rule is source A needs to be higher up in elevation than source B. Apply a little suction to the end that's in source B and boom, all of the water from A moves to B with no additional suction because each water molecule is pulling the others it's attached to along behind it, kind of like a train. This train will \"break\" when the water levels in the U are back to equal, i.e. where the pipe levels back out. Oh, and there is one other reason these exist-- they're really helpful if you drop something down the drain that you wish you hadn't, like a ring or whatnot. These things usually require more pressure to move up the second part of the U than is provided by running the sink, so if you realise what you've done, you can undo the trap and get your nice thing back.", "Others have told you what and why, I will confirm it is important. Have a bathtub in the house that never gets used. I have to pour water down the drain every few weeks to refill the p-trap when the water in it evaporates. Otherwise I get to enjoy the smell of my septic system." ], "score": [ 170, 75, 69, 10, 8, 7 ], "text_urls": [ [], [], [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkn5uqu" ], "text": [ "[File:Zipper animated.gif - Wikipedia]( URL_0 ) They stop working if something gets damaged that causes them to no longer link together properly" ], "score": [ 17 ], "text_urls": [ [ "https://en.wikipedia.org/wiki/File:Zipper_animated.gif" ] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkolwgk", "gkoi98i" ], "text": [ "If you're going directly with the wind, you're right, you can't. If you're moving the same speed and direction as the wind, there is no wind. Relative wind drops to zero. Now say you used a motor boat to go the same speed as the wind, but perpendicular to it. Is there still wind? Absolutely, depsite the fact you are going the same speed as the wind, the entirety of the wind is still there. May seem obvious, and took a motor, but let's run with that fact and exploit it. Motion perpendicular to the wind does not remove the wind at all, only motion with the wind. Let's consider moving 45° off the wind. If you're moving the same speed as the wind, there's still wind. Your speed in the direction of the wind is only 70% (cosine (45°)) of the wind speed. 30% of the wind speed is still there. You'd need to be moving at at 143% of the wind speed to have zero net wind. Therefore, even the most basic of sail can still be pushed by the wind if you're moving 45° off the wind at the exact same speed as it. If you're moving at the speed of the wind, but 70° off, your only moving in the direction of the wind at 34% of its speed. You'd need to move at 292% of the wind speed to see zero wind. So as you can see, by going at an angle off the winds direction, you need to go at a much higher speed before you see the wind vanish. Obviously, going to extreme will mean the wind gives a diminishing push on the sail, and that might not be able to overcome drag through the water. There is a limit and an optimum angle, unique for each boat and sail. So long as you're making the wind force on the boat divert some of the momentum sideways, you can reach a higher speed than the wind itself. How do you do that? Well, similar to how a rear wheel drive car steers, back wheels are only pushing forward, but the turning of the front wheels pushes off the ground to divert some of this sidways. A boat does this with the water. It's also similar to gravity and a slope working to move a ball sideways, not just down. Gravity of course has no speed it vanishes at, wind does. But the sideways motion gravity can create from the slope is like the sideways motion wind can create from the water on the hull. You can view it as the boat being squeezed forward between the water on the hull (which is preventing it from going directly with the wind) and the relative wind, not just the boat drifting with the wind. So long as there is still wind relative to the boat, you can still get momentum out of it. You can even go against the wind (though not directly), as some of the wind (relative to the boat) can be used to push you at an angle against the wind. How to do this efficiently is a more complex question and humans have been mastering it for quite some time. Modern aerodynamics can even explain how advanced sails are like an airplane wing, not just recieving a push, but a low pressure pull on the other side. But that complexity is not needed to say how it can happen, just how to do it well. So long as you can push against something (the water) to direct some of the momentum the wind is giving you to the side, you can keep the using the wind for more speed even if you exceed the speed of the wind. There's still wind relative to you if you're speed is directed partly sidways. Don't need advanced rigging or aerodynamics to do that.", "Modern sailboats don’t use the sails as a parachute that catches the wind. They use it as an airfoil that produces lift. The sail ends up acting like a very large vertical wing. I am fairly sure ancient sailboats did the same...but I’m not informed on that particular topic." ], "score": [ 11, 8 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkpdobe", "gkpixj4" ], "text": [ "Denser or more viscous fluids require more power to pump at the same rate. Fluids with lower density or viscosity can cause a pump to run faster than normal. Either case can cause more stress and fatigue in pump components. The particular thermal properties of the fluid can cause inadequate or excessive cooling. The fluid can be more corrosive, abrasive, or less-lubricating than designed for, causing excessive wear.", "This really depends on the type of the pump but assuming the most common centrifugal pump: If the pump engine runs faster than it was designed for, it will wear out the lubrication, bearings and commutators faster. It may also degrade the lubricant even faster faster due to the heat that more bearing load generates. This is more of a problem with enclosed pumps that cannot be serviced and is a rare problem in general as pushing fluids in itself sets a somewhat predictable lower bound for a pump workload. If the pump engine runs too slowly then it puts extra load on the individual coils in the engines armature(the inner spinny part) and/or stator(the outer enclosing part). The way electric engines work is by continuously applying power to a series of electromagnet coils arranged circularly in either the stator or armature or both. Individually these coils are too weak to be powered up for more than a few milliseconds at a time, the waste heat generated would degrade and eventually melt the coils when powered up for too long. If the engine is forced to run slowly, each of these coils spends a longer time being powered up and at some point this will destroy the engine. Most bigger modern pumps have some smarts in them that will automatically reduce the power if it gets dangerously slow but small or old pumps will just die while trying their best. Now as for oil pumps more specifically - these often rely on the oil that they are pumping for lubricating the turbine and for cooling the pump. They are most likely designed with a specific viscosity, heat tolerance and heat conductivity in mind. If the oil doesn't tolerate the heat its getting - the oil degrades and doesn't fulfill its purpose. If the oil doesn't conduct heat as well as it should - the pump may overheat and die. If the oil is too thick and hard to push around - it might kill the pump due to internal heat of the pump." ], "score": [ 5, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkpp6tj", "gkq1s3i", "gkpp65a" ], "text": [ "The drill just spins. Think of it like a wrench. The impact spins, but with a rotating hammer. Imagine a wrench where, when it gets too hard to turn, you tap it with a hammer instead of just pulling with your hands. Impacts can output way higher torque, but this can be excessive for many tasks, and break bits. They also aren't good for making holes is things (drilling), and are exclusively for driving/tightening. The circular saw and reciprocating saw can be used to accomplish many of the same tasks. In general, I find the circular saw to be more precise, but also less versatile.", "a 5 year old... use the drill for drilling and the impact driver for driving screws! Im not being dismissive! it's just that simple. Circular saws are best for straight cuts on wood, or ply wood, especially if you use a guide. Reciprocating saws are often called \"saws-alls\" and their useful for when you have to cut something random or hard to reach. Saws-alls also have a few different blade options that are incredibly east to swap", "Impact drivers are generally better than normal drills, a little faster and have more power. For instance if you was driving 6inch screws into timber all day, you'd definitely want an impact. For domestic work the difference is minimal, however if you're a joiner you'd definitely want both to choose from. A reciprocating saw is used for cutting out pieces of wood, plastics and metals (blade dependant) at funny angles and on the fly. Generally more demolition related, it's manouverable and usually light weight. While a circular saw is usually used to cut straight lines fast and reliably for a nice clean edge." ], "score": [ 5, 3, 3 ], "text_urls": [ [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkrpg04" ], "text": [ "That's a short circuit. All it would do is trip the circuit breaker (if the circuit breaker works properly.) If it doesn't trip the breaker, it would cause so much current to go through the wires that they could literally catch fire." ], "score": [ 5 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gks8rj0", "gks9l0d", "gkslsmj", "gkscly6", "gks8w6b", "gksbg7x", "gkt4qbl", "gkut9xw" ], "text": [ "Because the metal on the heads likes to shear off if too much torque is applied. The result is a bunch of debate on what head is the best for what application which has resulted in a myriad of standards for screwdriver heads for every conceivable application. Then there's also bits that are specifically designed to be annoying. These are generally used in public spaces so some random person can't unscrew things to see what happens or take things. Going beyond this there's also certain heads designed to go in only one direction so that if something gets screwed in it can't be unscrewed. These are generally used for security applications like securing safes.", "Phillips is the standard Henry Ford went with because the superior Robertson drive was too expensive to license.", "The problem with setting standards in industry is that it's nearly impossible to accomplish. Everyone ends up picking different standards for different reasons unless the government acts to enforce it by law. Look up the European Union and cellphone chargers for an example. The earliest screws were flat heads because they were the easiest to make but they are annoying to use because the screwdriver keeps slipping out of the head. So inventors tried to invent a better screw. The Phillips screw (star type) and the Robertson screw (square type) were invented at around the same time, but like so many other things were protected by patents. The story goes that Henry Ford helped standardize the Phillips screw in the US because while Robertson had the better design he wouldn't license the patent to Ford because he had too much bad previous experience chasing down people for violating his intellectual property not paying royalties. Since then other types of screws like torx (6 headed) have been invented that are arguably better but are even harder to manufacture. These types of screws often gain popularity because they make stuff relatively tamper proof and manufacturers don't like it when people try to repair things themselves.", "For two main reasons. Reason 1: URL_0 Reason 2: Because some screws are designed to be proprietary to prevent tampering. This usually results in a new style as the old style becomes commonplace.", "Flat Head screws are a throw back to the beginning of the industrial revolution. They have been superseded by Phillips head. The reason for this is increased mechanization in manufacturing. Phillips Head screws are great for self centering machines used in assembly", "There are also some proprietary bolts used by companies to difficult third party or self maintenance like Nintendo does with most of its consoles.", "flatheads are primitive, yet effective. can be cleaned out easily, not an actual screw driver is needed and they're cheap and easy to produce. in my opinion best used on medium sized to larger screws. phillips was the stopgap version before we knew better models, but now old. personally, big fan of torx.", "Because the Robertson screwdriver is much better than the Philips or the flathead. The only reason it's not the defacto North American standard is Henry Ford wanted to buy the patent from Robertson, a Canadian inventor and Robertson refused. Miffed, Ford vowed to never have a Robertson screw on a Ford product again." ], "score": [ 107, 22, 20, 10, 8, 3, 3, 3 ], "text_urls": [ [], [], [], [ "https://xkcd.com/927/" ], [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkt2xcg", "gkta3bo" ], "text": [ "In general structures like the GGB are designed for an effective lifespan of about 100 years. It's not really an expiration date though, as it's actual lifespan will depend on how much they're willing and able to spend on maintenance. With enough maintenance it could hypothetically continue to be used for as long as it is desired, but realistically it becomes a monetary question - is it cheaper to keep replacing the old parts on an increasingly frequent basis, or would it be more cost effective at some point to tear it down and build a replacement. This is basically what happened with the iconic and beloved old Yankees Stadium (the house that Ruth built) - at a certain point they were spending so much money every year repairing the crumbling structure of the stadium that they ended saving 10's or 100's of millions of dollars by building a new one. The most recent estimates I've heard is that they currently spend about $65 million each year on maintenance for the Golden Gate Bridge, they collect roughly $100 million from tolls each year, and to replace it would be in the neighborhood of $8-10 billion. So they're likely to continue with the maintenance approach for the foreseeable future.", "Have you ever taken a bendable piece of plastic or thin metal, like the clip of a breadbag, or the opener on a drinking can and bended it back an forth until it just snapped? This is what we call material \"fatigue\". After being repeatedly bended and twisted the material eventually becomes \"fatigued\" and will grow weak to eventually break apart. During the bridge's lifespan, the structure's material will be constantly bended and twisted in small amounts due to the loads of cars and trucks passing over, thermal expansion, and the effects of wind and weather. The structure is designed to be able to withstand this, ofcourse. But eventually the very material the bridge is made out of is simply just worn out and it will have to be rebuilt completely. This doesn't just apply to bridges either. It also very much applies to airplanes, pressure tanks, springs, ships, basically anything that experiences rhytmical bending, twisting, expanding and contracting, because of material fatigue." ], "score": [ 18, 5 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gktnb5f", "gkuh4j1", "gktmlno", "gktzfhx" ], "text": [ "It's not because of the angle of the rear window, it's because of how much dirt sprays up from the back of the vehicle. On most cars, the trunk is between the rear window and the back of the car, and the window stays relatively clean and dry from road spray from the back of the car. On minivans, hatchbacks, station wagons, etc... The rear windows get very wet and dirty simply from driving on a wet road, so you need a way to clean the rear window for visibility. Though the angle of the rear window might affect how well rain washes the rear window, generally car rear windows stay cleaner. Also, pickup trucks have a steep (vertical) rear window, but no wiper, because the truck bed is in between the rear window and the back of the vehicle.", "The air flowing over the car abruptly detaches from a vehicle with a steep rear window while the air flowing over a vehicle with a more shallow rake to the rear window stays more attached and flows down the window and over the trunk. The effect of the detachment of the airflow on a vehicle with a vertical rear is to cause a turbulent region of low energy and relatively low pressure air. Just as pebbles and silt fall out of suspension in the water column on the low energy inside radius of a river meander so do particles of dirt and dust fall out of suspension in the air column at the back of a truck or Volvo station wagon. The area of low pressure behind a flat backed vehicle further sucks in more dirty air and the low speed of the air means that there is insufficient energy to dislodge any dirt on the car.", "The backwind created while driving at higher speeds pulls the spray a car makes onto the rear windshield.", "It's not how steep the rear window is that matters, it's how far away it is from the back of the vehicle and the rear tires. When driving on wet pavement, the rear tires kick up a constant stream of water, flung high into the air and some of this ends up spraying the back of the vehicle, even though it's moving forward. Vehicles with a traditional trunk have the trunk between this stream of water and the windshield, providing some protection. But hatchbacks, minivans, and other vehicles with rear doors and no trunks do not and so the rear window catches far more spray from the road than other vehicles." ], "score": [ 103, 7, 6, 5 ], "text_urls": [ [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkvcjbq" ], "text": [ "The primary difference is the order in which threads overlap. You can think of fabrics as being made of rows and columns of threads, more or less. The rows are called wefts, and the columns are called warps. A plain weave is a simple over one thread, under the next. If you ever did crafts in school where you laced pieces of paper together to make a lantern or a basket, that’s the same thing, but with threads instead of paper. A twill depends, since there are different types, but a common one is over two threads, under two threads. You vary when you go over/under a thread for each column, which creates an offset and the distinct diagonal pattern. So on one column you might start your over/under at the bottom of the column, and on the next column, you would start 2 rows from the bottom to make the offset. The waffle weave I’m not as familiar with, but from a quick look, it seems like you skip threads in a particular pattern to create the boxes. So you’ll go under one thread, then over four for a few columns to make your box shape, then a plain weave as described above for a few columns and rows to create a border around the box." ], "score": [ 3 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkvcrh7", "gkvcb3n" ], "text": [ "The basic idea is the same as shooting a spitball through a straw. High pressure in one end of a tube pushes something through the tube and out the other end. Pressure is created by burning gunpowder, an explosive that creates a lot of high pressure gas extremely quickly. A bullet is the blockage in the tube of the barrel and it is pushed out the other end at a high rate of speed. That is the basic concept. As guns became more complex and refined ideas like rifling, grooves that dig into the softer lead of the bullet and spin it to increase accuracy were invented. Cartridges were made that held the gunpowder and a pressure-sensitive igniter in place with a waterproof housing, and clips or magazines to hold multiple of them together for easy loading. Mechanisms to automatically insert, fire, and extract the cartridges add mechanical complexity to firearms. Ultimately though the same concept of action has held since the initial invention.", "In the simplest terms a gun is a tube with an opening at one end, and some method of starting an explosion inside the tube. Very early guns were basically just small cannons. Stuff some explosive powder and a ball down the barrel, then use a small hole at the back to ignite the powder with a match. [Here's a video that explains how a modern rifle works]( URL_0 ) with a good animation to show all the moving parts." ], "score": [ 8, 7 ], "text_urls": [ [], [ "https://www.youtube.com/watch?v=MgYlFHY3WmA" ] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkwan9m", "gkw9grw" ], "text": [ "I want to clarify what (I think) OP is trying to ask which is the COLOR TEMPERATURE of the led, and not a matter of led vs incandescent. I’ve actually wondered myself why they chose cool white (6000K) instead of warm/soft white (3000K).", "Because of the type of light. Old street lighting use to have Vapor halide. This type of bulb gave a warm or orange type. Since US and many parts in the world are moving to a more energy efficient technology that's LED. It all came down to power savings" ], "score": [ 3, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkwo61p", "gkwzgi9", "gkx1kfd" ], "text": [ "The boards have trace routes that connect the chips to power and input /output (IO) signals. Think of the routes as wires. The boards are designed in a computer program that includes the footprint of the chips that will be placed on that board. The engineer designs it so that all the chips have the proper signal and power connections. Many other factors are at play like keeping fast signals short and not localizing hot chips together. the chips can be passive (capacitors, resistors, inductors - which help clean up the power and signals) or active (the smart ones that do the logic, like CPU, or IO, such as led lights, external connections). Edit: besides the stuff you can see, there is also software that is used to do the logic for the programmable chips. So the combination of advanced chips on well designed boards plus the programming of chips on those boards that gives the magic we users enjoy in the end.", "At the lowest level there are the transistors which are electrical switches that have three wires. Source and Drain for input and output and gate for the switch. Voltage to the gate allows source and drain to connect current. At the next level are logic gates built from multiple transistors. There are AND, OR, NOT, NOR, NAND gates. for example a AND gate output will be a 1 if both its inputs are 1. Below is a picture of how these gates are constructed from transitors. URL_1 We can now construct Adders, Subtractors, Shifters and other data manipulators with these logic gates and transistors. For example here is a image of a Adder which takes two 4 bit numbers, adds them and outputs a 4 bit sum. URL_0 The collection of adders, subtractors, basic logic, shifters forms the ALU which is the heart of the processor. There are also multiplexers which routes data to different circuits and registers built from flip flop gates that temporary hold voltage over cycle. With all these parts, a clock signal, and memory you can construct a computer that reads memory, processes it and stores it. Todays computers are so complex that engineers just write code like Verilog that specifies which basic parts connect to which wires and the computer builds that most efficient physical map to be printed.", "The copper line on the green board (PCB) connects places where engineer wants the same voltage. So the purpose of the board is to transfer voltage signals. There are many routes because engineer wants some places to have say 5V while others 0V. There's 100s of these places on the board. However to achieve what modern computers do these days, they need millions and millions of different simultaneous places where voltage must be 5V or 0V (basically 1s and 0s). They also need millions of switches to control where goes 5V or 0V and at what time. How do they do that? They do that on the chip. Chip is a piece of rock (very pure silicon rock). They etch nanoscopic channels to pour in copper routes and selectively add impurities in other nanoscopic places to create millions of transistors (switches). After that it comes down to combining these electrical elements to create more complex devices. Transistors can be combined to make different kinds of logic gates. Different kinds of logic gate can be combined to make other devices on another abstraction level (such as flip-flops, multiplexers, all kinds of weird but interesting stuff). Then these devices can be combined to make even more abstract level devices such as ALU (Arithmetic Logic Unit which adds and subtracts numbers), registers, cache and others. These then are combined to make CPUs. After that the hardware side ends and the next abstraction level is software." ], "score": [ 5, 3, 3 ], "text_urls": [ [], [ "http://www.interfacebus.com/ic-adder-chips.html", "http://www.justgeek.de/wp-content/uploads/2014/07/gates1.png" ], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gkx31qn" ], "text": [ "Ventilator isn't just a oxygen providing tool. Its a automated pump designed to FORCE air down." ], "score": [ 4 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gl13x5i" ], "text": [ "The primary difference is the tempature at which the rubber remains soft and malleable. Summer tires need to be a lot warmer, but will wear less and offer better grip in dry conditions, Winter tires provide better traction in colder tempatures, but will over heat and abnormally wear in hot conditions. & #x200B; All season tires basically just suck at everything." ], "score": [ 8 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gl1ghqn", "gl1ikrb" ], "text": [ "Good question, this is done so that if there is a fault it dumps the electricity into ground instead of whatever device that causes the fault, instantly overloading the breaker and causing it to flip, the other reason is due to how the US (assuming that you are from the US) is actually a 240v system with a transformer that outputs -120 (black) 0 (white/ground) and +120 black as well, so because of this neutral is actually the same as ground.", "My instructors in school (apprentice electrician) have explained it like this: If it were an ungrounded system, and a fault to ground developed on one of the hot wires, and you touched the other hot wire, it would be a 240 or 208 volt shock (North America’s line-to-line voltages for single phase and 3-phase normal use circuits). Because we ground the neutral, touching one hot while standing on the ground does expose you to 120 v, but they seem to be not as concerned about that. “At least this way, nobody can get a shock larger than 120 by only touching one wire”. Also, a fault to ground of one hot line will usually trip a breaker or blow a fuse due to overload. This all said, I am still not entirely sold on it myself." ], "score": [ 6, 6 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gl42w4c", "gl4e5n6" ], "text": [ "Can you provide an example of what you're referring to? Baseball pitchers lift both legs off the ground at different points during the pitch.", "Baseball players do lift their legs off the ground when they pitch. It’s a Pretty common thing and Pretty much all baseball pitchers I’ve ever known do it so I’m not sure how you haven’t seen it lol. It helps them gather momentum." ], "score": [ 10, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gl4lmo4" ], "text": [ "Assuming that they're both OLEDs (not all phones or TVs are), it's not a technology difference, it's a usage difference. Burn-in only happens if you keep an image static at high brightness for a long time. That's not uncommon with TVs that show the same menu or image for potentially hours at a time. Phones, on the other hand, typically only have an active screen while we're using them, they shut off the screen to save battery as soon as we're done, and they adjust brightness on the fly. So even with static imagery, a phone accumulates hours on the display more slowly and at lower average brightness. It's not \\*likely\\* on either device in normal usage, but a TV is more likely to run into the usage conditions that can cause it." ], "score": [ 3 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gl53pdn" ], "text": [ "It floats because as big as it is, and as much steel as its made out of, it still weighs less/the same as an equivalent volume of water it displaces. Water.. is heavy. Solid steel is heavier, but a hollow steel box is - comparatively - way less heavy than an equivalent solid steel or block of water. Ergo... it floats." ], "score": [ 20 ], "text_urls": [ [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gl86qtf", "gl8cd1u" ], "text": [ "Those numbers are the caliber, which is a measure of the diameter of the gun barrel and the ammunition that fits it. The larger the number, the larger the bullet, which generally makes it more powerful. But keep in mind that calibers that are less than 1 (e.g. .50 and .45) are measured in inches instead of millimeters, so .50 is equivalent to about 12.7mm.", "Generally these numbers are roughly the bullet diameter either in metric or in hundreths of an inch. But they are nominal numbers, which are not always the actual dimension. In NATO metric designation the numbers are *nominal* *bullet diameter x case length.* So 9x19 is a 9mm thick round stuck in a 19mm long case, 5.56x45 is a 5.56 milimeter thick round stuck in a 45mm long case. American round tend to be named by the bullet diameter in hundreths of an inch, so .40 is not 40mm as some journalists seem to think, it's 0.40 inch which is roughly 10mm. Older black powder rounds tend to have a dash in their designation, like 45-70. In that case the first number is caliber in hundreths of an inch and the second number is how much black powder in grains the cartridge holds The problem is that the number is very rarely exact because there is no universally accepted naming convention and different ways to measure plus marketing considerations come into play. So is the number you are looking at the diameter of the unfired bullet? Is it actually the caliber (barrels have lands and grooves in them, caliber is the barrel diameter measured land to land). Is it the barrel diameter groove to groove? Is it an arbitrary number selected to make the round stand out? For example 38 Special is the same diamter as 357 Magnum. You can even fire 38 Special out of 357 magnum revolvers. 44 magnum is actually .43 inch in diameter. 300 Winchester Magnum is the same diameter as 308 Winchester. 9mm Luger and 9mm Browning which is also called 380 ACP are also the same diameter, but it's not 0.380 inch, it's 0.355 inch and to make it even worse, 9mm Makarov is not actually 9mm, it's 9.27mm." ], "score": [ 15, 3 ], "text_urls": [ [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gl975ob", "gl9lrxc", "gl9k5ds", "gl9n1n6", "gl9efvv", "glatn7p", "glaovn7", "gl989yz", "glakqo1", "gla1i9c", "glb2s98", "glat6ax", "gl96xto", "glbubu9", "glbee3g", "glb19jn", "glb76hu", "glatuff", "glb2pww" ], "text": [ "Carbon fiber is light, but strong. If your Hitting Thingy is heavy, then you'll get tired much more quickly from swinging it around. If your Hitting Thingy is weak, then it'll break from you hitting things with it. Carbon fiber solves both of those problems.", "Carbon Fiber also has some great energy transfer properties. In the skating world, the amount of energy your foot can transfer to the ice greatly differs by the materials between your actual feet and the actual ice. So using full one piece carbon skates (relatively new to hockey and figure skating, but been around for over 20 years in speed skating) has led to much higher levels of efficiency. I can elaborate more on this if anyone is interested since this is my field of work.", "One important aspect of carbon fiber (its actually colloqiual shorthand for something like \"carbon fiber reinforced polymer\") I haven't seen mentioned yet is the fact that it is a composite material. Composites can combine some of the properties of its constituents and can be tuned more than homogeneous materials. Carbon fibers are woven together in strands/sheets and encased in a polymer of some kind (epoxy etc). The fibers can provide rigidity in specific directions while the polymer keeps the fibers from buckling. Different weaves of fibers and polymers can be chosen, combined in different ratios, patterns, directions, shapes etc. etc. to create materials with a large range of properties. Parts of the overall product can be finely-tuned in this way: head of a raquet vs the handle, seatstays vs chainstays on a bicycle etc. All of this contributes to weight savings as well.", "To answer your edit that you asked again multiple times in the replies, tensile strength is important in that you don't want your stick to break. Specifically, you don't want it to break when flexed, and more strength means more force can be applied before breaking. It's not the tensile strength they're really after with the carbon fiber though, it's the stiffness. Stiffness in materials science refers to a material's resistance to bending. If I have to put a lot of force to get a little bending, my material is stiff. This is really important for stuff like golf clubs and hockey sticks, because if my stick is really stiff, a little bit of flex absorbs a lot of force. When the flex is released (ie: when the ball or puck is hit), that force is transferred to the object, making it fly faster and further. You can see how important that bending is in [videos like this]( URL_0 ). Carbon fiber is among the stiffest materials in the world (along with being lightweight and strong).", "Concrete is very strong in compression, but only worth 10% of it's strength in tension. That's why it's easy to bust a chunk of concrete, because when you bend it, you compress one face and stretch the other. That's why we put steel in Concrete. It has a really high tensile strength, and prevents the block of concrete from pulling apart, making it super strong. But steel and concrete are really heavy. Steel is strong, but not really all that strong when you break it down to thicknesses measured in micro-millimeters. Carbon Fiber on the other hand is CRAZY strong. But it's also really thin, so it behaves more like rope or string. Great in tension, but not good for pushing on. So, you surround the Carbon Fiber in something flowable and rigid like Concrete. In sports equipment, that's usually some kind of plastic epoxy thing that can be engineered with exact hardness vs bendiness specifications. The Carbon Fiber will make sure it never breaks or cracks, and will fit whatever form you put it in.", "TL;DR: There's three things you need to know about Carbon Fiber (CF): 1. It's light, means swing faster, means can hit things with more energy. 2. It's strong; either in one direction, or many directions. You can tailor the characteristics of the CF in one or more directions depending on the application. 3. It combines with other materials well. Compounded with the custom strength directionality, you can use resins or other materials to take advantage of their elastic, or rebounding properties to get out more energy than you put in. (Look at a [hockey stick flex in slow motion.]( URL_4 )) Long, maybe an ELIgrade9 or ELIgrade10. Review: There's three things you need to know about Carbon Fiber: 1. It's light. 2. It's strong; either in one direction, or many directions. 3. It combines with other materials well. 1. Weight plays into a factor when looking at sports sticks that hit things like hockey sticks, badminton rackets, tennis rackets, baseball bats, golf clubs, etc., because the more weight you add, the harder it is to swing the stick. The easier it is to swing this stick, not only is it less effort, but you can also impart more *kinetic energy* into the object you're hitting with the stick (ball, puck, shuttlecock). The equation for Kinetic Energy is: `KE = 0.5 * mv2` Where *m* is the mass of the object, *v* is the velocity of the object that is moving. The important part to focus on is the *v**^(2)* term, which is a product of the *SQUARE* of the velocity of the object. This means the faster you swing, the energy goes up like.. REALLY fast. For example, swinging a 2kg object at different speeds this is what you get: & #x200B; |Object weight|Velocity|Kinetic Energy| |:-|:-|:-| |2kg|1 m/s|1 J| |2kg|2 m/s|4 J| |2kg|3 m/s|9 J etc... | |3kg|1 m/s|1.5 J| |4kg|1 m/s|2 J| |5kg|1 m/s|2.5 J| So as you can see, increasing the speed of the object increased the KE *much* faster than increasing the weight. That's why head speed in golf is so crucial for maximum distance. (also why the longer clubs go farther, larger arc etc... that's another ELI5 entirely) 2. Carbon Fiber is actually just that, it's fibers of Carbon material, literally woven together like your rug, or t-shirt is. It can be woven in many different patterns for different applications. The reason this is important is because the strength is entirely dependant on the *axis* of the weave. If you place all your fibers in one direction ([uniaxial/unidirectional]( URL_0 )), you have LOTS of tensile strength (which is where CF gets all its strength) in that one axis, but if you pull it apart in the other direction/axis, the fibers pull apart easily. If you offset these axis by an angle, now you have [biaxial/bidirectional]( URL_2 ) CF. Now the material is strong in two directions, typically offset 90 degrees from one another. You'll likely recognize it, as this is the most common \"print\" you can find on vinyl wraps, hydro dips, or other fake CF prints. There are more complex weaves (twills) that go into lots of details ripe for PhD research if you're so inclined. The other cool looking one is \"[forged]( URL_1 )\" CF, or chopped CF. Unfortunately, it's not forged in the traditional sense. Oftentimes it's created purely for an asethetic as the top layer that shows, and doesn't serve any significant structural purpose (AFAIK) due to the non-continuous fibers. It will also likely have a much worse strength/weight ratio, as pure \"forged\" CF will have a higher density of resin. 3. CF is oftentimes referred to as a \"composite\" material, because it is. It is composed of many types of material, for instance you could have a \"forged\" CF top layer, two layers of uniaxial CF wrap, two more twill layers, and finishing off with two bi-axial, 45-degree offset layers. You've just created a composite sandwhich of Carbon fiber layers! However, if you don't add any bonding agent to this roll of CF, the hockey stick you tried to build will be floppy. You don't be hittin any dingers, or sniping any pockets with a wet noodle, now would ya bud? This is where the resin comes into play. It is the bonding agent that gives CF objects the *compressive* strength. It also contributes to the elastic strength a little as well, depending on the selected resin. You can also mix in a few different resins while you build, or *layup,* the carbon object you're building. The first layer to go down will likely be a UV-resistant overcoat resin that will protect the outside of the part. Next, maybe you'll use something like a quick-set resin to get that layup a stiffy before you take a break that night. To finish it off, there's a few tricky bends and bubbles you want to squeeze out so you use a long-set resin to really make sure that the final structure is perfect. So, as you can see, the CF product of any type is a gentle massage of getting many different materials of various abilities to work together, not just the Carbon Fiber. My favorite use of CF in my personal life is [my hockey stick]( URL_3 ). It's largely a rectangle with rounded corners and concave long sides, which makes it easy to hold in the hand, very comfortable, and the concave shapes give the shaft a little more stiffness while retaining the ultra-light structure. The best part I can't find a picture of, but the shaft tapers down to an elliptical near the blade, which isn't as stiff as the rectangle meaning the stick is very stiff uptop, but soft and playful down low. This complements quick loading for ultra-fast releases on shots, to catch an unsuspecting goaltender off guard. This is the sort of material manipulation you can only get using the miracle that is Carbon Fiber, or VERY expensive processes thinning walls and using generative design + 3D printers and metal. Hopefully someone enjoyed. I had a great time chatting about this with myself, so thanks for the ELI question!", "One downside to carbon fiber is that when it fails, it does so catastrophically. Bump into a car with a metal bicycle, and you might bend your frame. Do that with CF, and you probably busted something in two.", "That's basically it. Carbon fiber is light and ridgid. Player's strength and dexterity are wasted less on handling the equipment. Therefore, more energy or fine adjustment makes it to the ball, birdie, or puck. This is similarly true of cars, planes, and tools. Think of it this way: would you rather swing a one-pound racket or a ten-pound racket? Would you rather the engine push a half-ton vehicle or a two-ton vehicle? What's more maneuverable, a 500-pound plane or a 5,000-pound plane?", "Just popping into to say that there are no tennis racquets that use carbon fiber. Graphite is the preferred material", "Someone else mentioned it but besides being lighter, it doesn't transmit the shock of the impact to your joints like steel or aluminum will. The reality is any athlete can hold a hollow metal bat without any sort of challenge to their strength. Bat something with metal and then carbon fiber, you will notice a big difference. This is one reason carbon fiber is nice for road bicycles, it is strong, that it will not break, while flexing under you. The reason for this is while metals have atoms lined up in a crystalline formation, which gives it strength, that thing that gives it strength makes it extremely rigid. Carbon fiber is made up by many sheets of carbon, which can flex under load and return to the original shape after the load is gone. Have you ever seen a picture of a glider landing? The wings look like they are bent in the middle! [ URL_0 ]( URL_0 ) So, if that was traditional aluminum that force would be transmitted into the fuselage of the aircraft, which in that application would be undesirable. Quick note, most gliders are composite fiberglass, not carbon fiber, but it is the same basic idea. In fact, the 787 and a350 use carbon fiber extensively both for its weight savings, strength, and the ability to flex under load. So, if you have a composite bat, and you are hitting baseballs all day, the energy that is absorbed by the bat by flexing and returning to normal shape, that is not being absorbed by your joints, will reduce fatigue and injury in the athlete.", "The real question is, why in the US do we call it sports equipment, but have Sporting Goods stores?", "Carbon Fiber not really economical compared to other materials that have *just slightly worse* performance/physical characteristics, which limits its use in sports. What we all commonly call \"Fiberglass\" is a composite of glass fibers and a plastic resin. What we commonly call \"Carbon Fiber\" is a composite of carbon fibers and a plastic resin. Fibers made of carbon are more expensive than glass fibers... If you make two rackets, one of fiberglass and one of carbon fiber, you'll have a great cheap racket and a really great expensive racket. The cheap one is still pretty darn good, but it will weigh a tad more (silicon in glass weighs more than carbon). That's mostly what holds-back the proliferation of carbon fiber. As carbon fiber technologies mature their cost will continue to go down and their use will further expand.", "Carbon fiber has multiple application. It is used because of its light weight and extreme durability.", "Pessimistic answer: sporting people have money and carbon is great for parting it from them. Science answer: great stiffness and strength properties. Stiffer stick does what you want, floppy stick does kinda what you want.", "One sport I haven’t seen is Curling. Carbon Fiber handles have replaced wood and plastic curling brooms to reduce the weight. It allows greater transfer of energy to the ice and is less tiresome during the rigorous sweeping action.", "I think they also also produce better results. Anecdotally, players who I never thought could shoot well are now getting decent velocity on their shots. Players who can shoot before are now in able to fire howitzers at me. Source: Am (Hockey) goalie.", "Chess is a good example where carbon fiber wouldn’t be a great fit. The benefits of using carbon fiber pieces would be to delay arthritis and help reduce repetitive strain injuries. But the cost of producing carbon fiber pieces is more expensive than the wood and plastic currently used. Carbon fiber would only grant a very slight advantage on health, not in the game itself. Hope this helps.", "To your question about weird sports where carbon fibre is used, here is an example: Squash. Squash is a racquet sport similar to Tennis, but indoors with a smaller, different ball. It is a much faster paced sport, that requires quick and accurate movement/hitting. Enter carbon fibre racquets. They are much lighter than the wooden racquets of the previous generation, most weighting as little as 100g. This allows for players to be quicker, tire less, and hit much harder. In addition, the racquet faces were able to be made many times larger than in the wooden days, making it easier.", "As for weird sports I know carbon fiber is used in both sailing and archery. Both are because of it being lighter but more durable than traditional equipment. In archery, most higher level competitors have at least one set of indoor arrows and one of outdoor arrows. Like most people my outdoor arrows are really light and skinny carbon fiber composites with short fletchings. These are light enough to make it to the target that is 50 meters away and the extra airtime allows the arrows more time to correct themselves with the help of the vanes. My indoor arrows are much heavier and thicker aluminum arrows with substantially longer fletchings (4 in feathers compared to 1.5 inch plastic vanes). I can use helical feathers because of the increased drag and spin. This slows the arrows and provides for more corrective stabilization which helps even out mistakes since they are only traveling 18 meters and aren’t in the air as long. Using the right arrows also helps with tuning. I do not use a sight, so I have to aim using the point of my arrow. If I am outdoors, I typically have to aim at the top of the target to have my arrows go in the middle. If I were to try and use aluminum arrows outside, I would have to aim well over the target and I would not be able to be consistent since there is no reference point that I could use" ], "score": [ 6585, 747, 128, 125, 39, 17, 11, 11, 7, 6, 5, 5, 3, 3, 3, 3, 3, 3, 3 ], "text_urls": [ [], [], [], [ "https://www.youtube.com/watch?v=Nz_4i1e6ppM" ], [], [ "https://www.speednik.com/wp-content/blogs.dir/1/files/2015/08/2015-08-27_22-31-54-640x427.jpg", "https://vinzers.com/wp-content/uploads/2018/11/forged_s9.jpg", "https://www.speednik.com/wp-content/blogs.dir/1/files/2015/08/2015-08-28_20-47-09.jpg", "https://www.frontierhockey.com/images/portfolio/f11.1/f11.1-shaft-radius-large.jpg", "https://www.youtube.com/watch?v=IsCdywftyok" ], [], [], [], [ "https://www.youtube.com/watch?v=qC2yCoBQfDA" ], [], [], [], [], [], [], [], [], [] ] }

[ "url" ]

[ "url" ]

{ "a_id": [ "gl9x6lc" ], "text": [ "Answer: It's not the saw that knows, it's a seprate part called a SawStop that is installed into the saw housing. The SawStop gives the blade a small electric charge and when your finger (which also has a small electric charge) touches the blade, it completes the circuit and sends a signal to the SawStop to activate. Activation uses a spring loaded mechanism to bring the blade to a stop. Here's an explanation and some slo mo footage: URL_0" ], "score": [ 4 ], "text_urls": [ [ "https://www.youtube.com/watch?v=SYLAi4jwXcs" ] ] }

[ "url" ]

[ "url" ]