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vishnun0027

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{ "a_id": [ "gvtjtun" ], "text": [ "Well first of all you make sur that your steel will fail first. The reason is that steel have a elastic and plastic deformation phase. If you put enough force on the steel it will bend a little bit, but will get back in place after. But if you put even more force on the steel it will start to stretch in the plastic zone which never go back. The concrete will crack, but since the steel is still there it will keep it from exploding. The second part is that all the steel is at the edge of the concrete, it's never just in the middle of it. So the steel often work like a cage that will keep the concrete together. If we could we would put the steel at the very edge of the concrete, but that leave it expose to the element, water might reach the steel and cause corrosion. So we have what we call a cover, which is a minimum distance between the steel and the surface of the concrete to protect the steel. But the steel always start right after this distance. We also place the steel where it work the best. If you have a beam for example, and you apply weight in the middle of it. The beam will be in flexion, which mean that there will be compression on top of the beam, and tension at the bottom. So most of the steel will be at the bottom to take that tension. Source : I'm an engineer working on rebar." ], "score": [ 8 ], "text_urls": [ [] ] }

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{ "a_id": [ "gvugypa", "gvueqye", "gvufbrl" ], "text": [ "Train tends to be built on the tacks. You simply have tracks on the floor of the factory. You can lift trains with [jacks in a workshop]( URL_3 ) roll the train on jacks in the workshop to remove the bogie/ wheel. Stong cranes in the roof can also life the train. You can transport train on trucks like [like in this image]( URL_0 ) It is also possible to transport trains on ships, there are even [train ferries]( URL_1 ) where you just can [roll the train on and off]( URL_5 ). Or you can lift them [with cranes]( URL_4 ) Mobiles canes are also used to [lift trains back on the tracks]( URL_2 ) after the derailment. The crane on the image is a railroad crane so it moves on the tracks but you can use wheeled cranes too.", "> or do they just build the train on the tracks? exactly that: the train (or the railroad car) will be usually build in a factory with access to the rail network. Other than this you can transport them on other vehicles (trucks, boats..even planes) and put them on rails at their destination.", "Depends, really. Some places can build trains then have to move them via road to their destinations (like the A1 Steam Loco Trust in Darlington, England), most places however build trains on the tracks then just run them like that" ], "score": [ 16, 12, 3 ], "text_urls": [ [ "https://www.alamy.com/reid-freight-heavy-haulage-longer-heavier-vehicles-with-trailer-lhvs-carrying-old-restorable-railway-carriages-for-restoration-by-a-train-pwrs-poulton-wyre-railway-preservation-society-image348906110.html", "https://www.alamy.com/stock-photo-train-cargo-ship-on-the-sea-20400579.html", "https://cf-images.eu-west-1.prod.boltdns.net/v1/static/4221396001/8be66c14-a199-4241-947b-889e06ec8046/738df235-6553-4e46-9e6d-2b27f87f8a59/1280x720/match/image.jpg", "https://www.pfaff-silberblau.com/mediadb/25039115/25039137/SliderElement.jpg", "http://www.mbm-consultancy.com/wp-content/gallery/lifting-frames/Train-lift-frame.jpeg", "https://www.alamy.com/stock-photo-unloading-the-industrial-cargo-ship-with-train-locomotive-ilyichevsk-86329306.html" ], [], [] ] }

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{ "a_id": [ "gvva6kq", "gvvaoky" ], "text": [ "Internal combustion engines can't go too slow. As they approach their minimum speed they have very low torque (can't work very hard). If you use a gear that's too high you prevent the engine from going fast enough. If you've ever ridden a bike up a hill you know what it's like, except that engines work using explosions that give like one hard push on each pedal per turn. If you go too slow, the pedal never makes it into position for the next hard push.", "A normal gas engine doesn't generate much power or torque when it's running slowly. This is because the pistons in a normal four stroke go up, down, up, down - four strokes - and only one of those is a power stroke, i.e. fuel is being burned to create power and push the engine around. There are more cylinders which spread this unevenness around a little, but the takeaway point is the engine isn't generating power for 360 degrees of its rotation, some of that is taken up by a flywheel to keep it turning while fuel isn't firing. If you slow the engine down too much, it can't keep turning far enough to get to the next power stroke without slowing down too much, to the point it stops. That's a stall. It doesn't happen in an automatic because the system is designed to disconnect the engine from the transmission when it slows right down, precisely to stop this happening. It happens on a manual transmission because you're in control of everything happening, and if you don't do things right, you can induce a stall. In your instance if you're driving up a hill, is this from when taking off from a stop or just when you go up hills? If it's when you're trying to take off up a hill, you're not putting enough gas in when you lift the clutch, that's all it'll be. If it's when you're driving and you get to the point when the engine stalls as you're going up hill, you should've changed down a gear or two as you hear the engine slowing. That exchanges forward speed for torque - the lower gears in the gearbox give the car more hill climbing power at the expense of forward speed." ], "score": [ 11, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gvvcqte", "gvvcrpz" ], "text": [ "Rolling stock (cars and engines) are routinely tested my driving them over special instrumented track segments. Most rail yards have these on the track approaching the yard. Railroad track is similarly inspected by a special inspection vehicle called a speeder. Most track is inspected once a month in the US Amtrack corridor, less frequently in remote places.", "Trains and parts need to be inspected every year. Consumables and safety equipment like brakes may be more often or based on mileage." ], "score": [ 5, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gvvpv4p" ], "text": [ "Many satellites use gyroscopes or reaction wheels to orient themselves. While you could use thrusters, gyros don't cost you any fuel." ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gvx82yy", "gvx8psa" ], "text": [ "Before Galileo, Copernicus had already come up with the idea that the Sun was at the center of the solar system. Galileo knew about Copernicus' idea and accepted his theory. With a newly invented telescope, Galileo was able to observe Venus and discovered that Venus went through phases like we see with our moon. The phases didn't fit the idea that Venus was travelling around the Earth and could in fact only be explained by Venus going around the Sun. Galileo concluded that Venus must travel around the Sun. Galileo didn't actually prove the Earth revolved around the sun. He only proved that the Earth wasn't the center of the universe.", "The idea of heliocentrism wasn't proposed by Galileo. One of the proponents of this model in Europe of the 1500s was Copernicus. But the idea goes back centuries/millenia. Using better telescopes, Galileo observed other planetary moons orbiting their planets and other phenomena that gave more validity to the heliocentric theory. In that sense, he didn't figure it out, he \"simply\" gave better observations." ], "score": [ 22, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gvxbbqc", "gvxau08", "gvz3xbq", "gvxdhw7", "gvxtchy" ], "text": [ "You don't want it to get manky or dry out. So it needs to be in a closed container without air, and you don't want to be touching the bulk of it. Also you don't really have a suitable tool to scoop it out of e.g. a tub. So the options are pretty much a flexible tube or an airless pump. You could probably do aerosol toothpaste like shaving gel, but it is much gloopier so might struggle to come out.", "You can find toothpaste tablets or pucks now that help reduce waste. I guess one of the reasons it comes in a tube because it keeps your toothbrush from touching the paste inside of the tube which could spoil it.", "In fact, in Croatia it comes in a bucket, the most common presentation is 2Kg Funny Source: URL_0 Edit: It was 2Kg, originally I put 10kg Edit 2: that was a lie, toothpaste buckets never existed, apparently everything was always a joke. A joke which I naively believed and told many friends about the strange presentation of toothpaste they use in Croatia", "theramed does this. dont know if its in your country (i am from germany). it works like a bottle with shaving cream", "There are companies who don't put it in a tube, rather a pressy pumpy thing - well here where I am anyway!" ], "score": [ 141, 25, 4, 3, 3 ], "text_urls": [ [], [], [ "https://crafty.diply.com/147260/croatian-twitter-user-learns-other-nations-dont-sell-toothpaste-" ], [], [] ] }

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{ "a_id": [ "gvy75w3" ], "text": [ "There aren't that many electrons in play A person has a capacitance of less than 1000 pF normally. If you build up a static charge that gets you to 10,000 Volts (not unreasonably high), that's just 10 uC of charge or about 10^13 electrons. A 1 milliamp current moves 1 mC of charge(10^15 electrons) every second and that's a pretty low current. Your standard multimeter has an internal resistance that it is taking the voltage measurement across, this is usually pretty high (10 MOhms ish) so it only lets a small current flow, but since you only have a tiny amount of charge it dissipates very quickly. If you put 10kV across 10 MOhms, you'll get 1 milliamp of current which will dissipate that 10 uC of charge in just 10 milliseconds. If you want to be able to measure the value without really changing it then you're going to need something that doesn't permit much if any current to flow. Field meters don't actually make physical contact with the person/object that is charged up, they measure the electric field created by that charge but avoid creating a path that allows that charge to move around and dissipate" ], "score": [ 6 ], "text_urls": [ [] ] }

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{ "a_id": [ "gw0jjz1", "gw0izsv" ], "text": [ "Some airports have various runways aligned in different directions to optimize operations even if winds are flowing in different directions. If this is the case, it could be that the approach/takeoff patch above your house would not be used since other runways are aligned more favourably with the winds at that time.", "The number of flights is because commercial flights are \\*highly\\* variable by time of day and day-of-week. Tuesday/Wednesday/Thursday are usually dead, Monday & Friday are really busy if it's a business destination, Saturday/Sunday are busy if it's a leisure destination. Airlines know this and schedule flights accordingly. Actual volume depends, mostly, on which aircraft it is and which approaches (the path over the ground the airplane takes to get to the runway) are in use. If the volume is scaling with the wind, it's because they're changing the approach direction. Otherwise it's probably just which approach is in use (which will depend on where the aircraft is originally inbound from, usually)." ], "score": [ 4, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gw0jxnt" ], "text": [ "Usually 2 main reasons. First, power. Hydroelectric power is cheap and clean compared to other sources of electricity. Second, water storage, which is mainly used for crop irrigation. Rather than pull from a river, you build a dam and back up the water into a reservoir and can pull water from the man made lake even when normal water levels drop due to season or drought." ], "score": [ 8 ], "text_urls": [ [] ] }

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{ "a_id": [ "gw4owmj", "gw4qjg6" ], "text": [ "The process is called laser ablation. When laser beam (usually pulsed) hits the material, some of the light is absorbed. Absorption heats up the top layer of the material. Since laser provides intense light, the top layer of the material gets heated to high temperature fast, causing it to sublime/evaporate or convert to plasma before heat can transfer to the rest of the material. This removes a layer of material. Remove enough and you can cut through. Obviously, high energy lasers are needed. Laser in the DVD drive will not cut through steel.", "You ever burn stuff with a magnifying glass and the sun? It’s the same thing, except we create the light and focus it in a certain way that it qualifies as a laser. The “cutting” technique is the same as the magnifying glass, just a lot more powerful. It doesn’t actually cut through it like a knife, but rather burns through it. Side note, if lasers interest you, check out styropyro on YouTube! He makes really fun and interesting videos all focused around lasers or chemistry" ], "score": [ 13, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gw4xx3z", "gw59oq9" ], "text": [ "The fuel will only combust in a mixture with oxygen, present in the air. As there's a persistent outward pressure of gas, oxygen can't get in, and the fuel won't ignite anywhere but at the escape point. In school science we learn to use bunsen burners as a demonstration of this: you can boost or cut-off the flame by adjusting the air inlet.", "Combustion reactions need oxygen. Here's an ELI5 equation for the chemical reaction that makes fire. hydrocarbons + oxygen + heat --- > carbon dioxide + water vapor + more heat. hydrocarbons are organic carbon and hydrogen molecules such as wood and fuel. & #x200B; C()H() + O2 --- > CO2 + H2O + heat & #x200B; What happens when you cover a candle? it almost immediately uses all the oxygen under the cover and burns out. That's also why you fan a fire to give it more oxygen to speed up the reaction." ], "score": [ 60, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gw558a9" ], "text": [ "They begin as round-ish rough pieces that are cut from raw steel stock. These pieces are rolled into a spherical shape in much the same way that you'd roll a ball of plasticine between your hands, except that the surfaces they're rolled between are very hard. For more precise bearings there are additional rolling operations, each one more precise than the last. I don't expect that electronics alters the process much, except that it probably makes the inspection and measurement stages faster." ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gw5dmvo" ], "text": [ "They use a sensor that can determine the movement of the camera in 3D space. This information is then used to move the motors at the joints of the gimbal to counteract this movement in each respective axis. It loops these steps constantly, and thus the camera remains stable." ], "score": [ 5 ], "text_urls": [ [] ] }

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{ "a_id": [ "gwa3rey", "gwa42tg", "gwa4pbr" ], "text": [ "Astronaut suits are designed to contain pressure inside while still being able to move. In the ocean it's the opposite, outside pressure is much higher than inside. An astronaut suit would be crushed underwater.", "The ocean is kind of the opposite of space. Since space is a vacuum, it has lower pressure than the inside of the suit, so there's no pressure against you, all the pressure is from the inside of the suit outward. The ocean, the deeper you go, the higher the pressure gets, so you need something very strong to resist that pressure. A space suit would just get squished along with your entire body.", "Space suits and vehicles are designed to protect the person inside from the vacuum outside. Deep sea diving suits and vehicles are designed to protect the person inside from the water outside. Water is different from vacuum. When in a suits in a vacuum you have the air inside your suit press against the materiel of the suit from the inside. When diving there is much greater pressure from the water outside pressing in on you. Space suits are designed to keep stuff in, while deep under the sea you want to the opposite thing of keeping water out. Instead of ballooning up like, well a balloon, under water you would have the issue of wanting to void getting crushed. The difference between the inside pressure of your spacesuit or ship and the outside pressure is at worst exactly one atmosphere. At the deepest bottom of the ocean a submersible has to deal with over a thousand times that pressure, pressing in on it. You can mitigate this somewhat by raising the inside pressure of your diving suit or submersible, but there are limits to what pressures human bodies can function at. This is why submarines are built with really strong hulls that can withstand crushing pressure, but spaceships tend to have very thin hulls. In space it doesn't take much to keep air in and extra mass is expensive to get into orbit." ], "score": [ 30, 10, 5 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gwajhhf", "gwajmgb", "gwalr8u" ], "text": [ "Firstly there are several different chemistries that are used in AA batteries. Some are more expensive and have higher capacity than others. The consider that a battery is not just a pot of chemicals. There are various components including a carbon anode, separator, exterior can etc. The quality of these affects the capacity and internal resistance of the battery. Edit to add: rechargeable batteries have even more variation because the robustness of different geometries to repeated cycling is not trivial to optimise.", "AA is just the size and voltage classification. Different materials with different internal structures can give off different amount of charges at the same voltage. Some Batteries need to provide large amounts of power for short time, others are used to keep a constant voltage over long times. If I used a Store brand battery for a professional camera flash, it'd probably be done after 10 uses. The 10x more expensive \"Alkaline Ultra Max infinity 3000\" can power my camera flash for like 500 uses but would definetely suck to operate my toothbrush because it isn't intended for long term applications.", "I noticed (back in the mid 90s when I had a pager for work) that different brand batteries acted differently as well. If I used Energizer, they'd show a slow but steady decline on the battery indicator on my pager. If I used Duracell, it would indicate that the battery was at \"full\" longer, but then drop like a rock when it was older." ], "score": [ 27, 10, 4 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gwfbtqg", "gwffn5q" ], "text": [ "Alright, let’s see what I can remember from Chemistry. This is going to be a very basic overview. So basically batteries work by creating/maintaining a voltage potential across two points (a.k.a either one point has a surplus of electrons or a deficiency, and the other is neutral or has the opposite). This is accomplished by using ions in an electrolyte, where through a chemical reaction the ions will either release electrons or absorb them to become neutral. Pop this in a container where the ions can’t themselves travel from one side to the other, or transfer electrons across, and instead need to transfer the electrons through an external path (I.e. a circuit), and you’ve got yourself a battery. If anyone would be so kind as to fact check me on that and let me know it would be greatly appreciated.", "Batteries contain a chemical as electrolyte which release electrons ....when we put batteries , say in a flashlight ....the circuit is complete and the electrolyte start releasing electrons ...and flow of electrons is called electricity ...hence electricity is created to light up the flashlight ." ], "score": [ 5, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gwebrpy", "gweho3d" ], "text": [ "Petrol engines have a spark plug which ignites the compressed air and fuel inside the cylinder. This creates an explosion which drives a shaft which transfers the momentum to the wheels. A diesel engine basically does the same but instead of a spark plug the cylinder just compresses the fuel and air mixture until it spontaniously ignites. The reason why a diesel engine does not use a spark plug is that diesel vapour is much harder to ignite. It requires a temperature of around +50°C I think. Standard gasoline vapour can be ignited at like -40°C. So in the diesel engine a standard spark plug does not create enough heat to ignite the fuel and air mixture and instead the cylinder just compress the mixture extra until it ignites by itself. (Compressing things makes them warmer).", "There are two key differences: Ignition - as mentioned petrol engines are ignited by a spark. This is handy because you can decide exactly when in the cycle to generate that spark. Diesel is ignited by the temperature of compressing the air. The advantage is that diesel can withstand higher compression than petrol which is good for fuel efficiency. Speed control (throttling) - for petrol you want to have exactly the right mix of fuel and air to perfectly burn all the fuel while using up all the oxygen in the air\\*. To vary the power of the engine you reduce the amount of fuel and the amount of air entering the cylinder on each stroke. Historically the fuel and air were mixed automatically in a carburetor, and then a throttle valve restricted the amount of fuel-air mixture that was drawn into the cylinder. Now it is more common to restrict the air in the same way, but to directly inject the correct amount of fuel into the cylinder. In contrast in a diesel there is no restriction on the amount of air drawn in. Only the amount of fuel injected is varied. Diesels never have carburetors. This means that diesels except when flat out always burn lean, meaning there is excess oxygen. \\* Modern petrol engines actually alternate between burning slightly rich (excess fuel) and slightly lean (excess air) to maximise the effectiveness of the catalytic converter at extracting various things from the exhaust." ], "score": [ 15, 5 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gwfbug7", "gwfb793" ], "text": [ "*Forgetting the external factors like air resistance, what is internally the reasons for a car not being able to travel above it's top speed?* ??? This is the #1 to factor that the engine is trying to overcome once you’re going above a crawl. At top speed the engine is primarily trying to overcome air resistance. Beyond that though - the pistons in an engine can only move up and down so fast before either the stresses on them exceed their design values or they hit a limit where they can’t draw fuel into the engine at a fast enough rate to keep up with the engine cycling.", "1) Thermal limits. Faster engine generates more excess heat. Eventually things fail due to temperature, things melt etc 2) Mechanical friction. Friction increases with speed. Internal engine parts rub against each other. 3) Strength of parts. Faster engine speeds put a lot more strain on parts which will break, things like piston rods, crankshafts 4) Design limitations. The engine is designed to suck in and use a certain amount of air each revolution. At high speeds, air is limited. The fuel injectors cannot deliver enough fuel. Engine valves cannot open and close fast enough. 5) Speed of chemical reaction. Ultimately a car engine relies on a small \"explosion\" of fuel and air in the piston. Although this explosion is fast, it is not infinitely fast. At some point the speed of the explosion is not sufficient to push the piston and the engine can no longer produce more power." ], "score": [ 18, 5 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gwg2lsa", "gwg2hp7", "gwg260o", "gwg2ekq" ], "text": [ "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 2,000 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. Most cars tend to be their most efficient around 50 - 60 mph. That's because that's where your highest gear puts you. You can keep going faster, but you're making the car work harder and harder for every 1 mph you go beyond its maximum efficiency. Eventually, that tops out and you either reach the max speed the car can possibly get out of that gear or you red line the thing and blow it. Your speedometer does not dictate the top speed of your car. The gauge could go up to mach 3 and your stock Honda Civic off the lot is only ever going to go maybe a buck 20 on the highway and you'd be pushing the poor bastard.", "Engines don't work most efficiently at their highest speeds, so to reduce the amount of gas needed at high speeds, car engines are made to go faster than the highest speed limit they'd regularly encounter. And there's no real downside to allowing cars to get that fast, because 99% of people simply won't try to get to their max speed.", "Sometimes it's necessary to speed up to avoid dangerous situations. Also, cars are sold throughout the world with different countries having different laws regarding speed limits. There's no \"one size fits all\".", "Every country has different speed limits. Some/most countries, like the US, only have speed limits for public roadways. If you're on your own property, you can drive as fast as you'd like. So it doesn't make sense to artificially handicap your product (compared to the competition) and at the same time lose out on market share (the adrenaline junkies/speed demons will buy other cars)." ], "score": [ 20, 7, 6, 6 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gwgn8e7" ], "text": [ "A bubble of gas in a liquid can collapse (compress into liquid) under the influence of a strong pressure wave, something like a very loud and high pitched sound. This rapid compression from liquid rushing to fill the gap, rebounding and compressing again etc. is strong enough to rapidly raise the temperature there to more than 10,000 K. The liquid becomes white-hot and you can see visible light coming off. It’s like a tiny supernova!" ], "score": [ 8 ], "text_urls": [ [] ] }

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{ "a_id": [ "gwhaint" ], "text": [ "A high open circuit voltage, means lower power losses in the wires. But high voltage comes with its own problem, the need for better insulation. As with most engineering, it's always a compromise." ], "score": [ 4 ], "text_urls": [ [] ] }

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{ "a_id": [ "gwhfghe", "gwhf07i", "gwhspqc" ], "text": [ "The corners are a stress point in the window frame. The sharp corners makes it easier for a crack to start in the metal. [More than one early airliner was destroyed]( URL_0 ) because they had square windows.", "That is a good guess. Corners are where stresses concentrate. Avoiding them where possible is a good idea.", "Yea pretty much. Sharp corners concentrate force and cause cracking from repeated strain from the pressure delta in and outside the aircraft." ], "score": [ 21, 10, 4 ], "text_urls": [ [ "https://en.wikipedia.org/wiki/De_Havilland_Comet#Comet_disasters_of_1954" ], [], [] ] }

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{ "a_id": [ "gwhc37r", "gwhcd8a" ], "text": [ "The stones are there for drainage. It stops from accumulating, which can freeze in winter and cause the ground to move and destabilize the track. It also discourages plant growth, which can also destabilize the track. This is why you may see weeds in shunting yards, but you will never see them on high speed lines.", "Stones = Ballast. It is used to bear the load from the railroad sleepers/ties, to help drainage, and to control vegetation that might interfere with the track structure" ], "score": [ 6, 4 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gwjmtm5", "gwjnsgz", "gwjr7l2", "gwjve04" ], "text": [ "There’s a little cable which runs between the truck and the trailer and can easily be disconnected when removing the trailer. This cable carries electricity and the brake light signal, which turns on and off the brake lights when the truck brakes.", "Trailers have wiring harnesses which stretch all the way from the back to the front of the trailer, which can plug into any tow-capable vehicle. At the the front of the trailer, the harness has a unique plug which fits an outlet wired into to the truck. It is about as simple as plugging in a lamp to an outlet in your home. Once plugged in, anytime the tow vehicle's own tail lights are engaged (braking, turn signals), the same signals are activated on the trailer.", "And adding to the previous comments, the connector is standardized, so all trucks and trailers hev the same connectors so its as easy as just plugging it in", "After a truck driver backs under a trailer, he has to get out of the truck and perform the following: *Hook up two (2) airlines between the truck and trailer that control the trailer brakes. *Attach a 7-pin electrical connector that controls the trailer lights. *Check and make sure the king pin is correctly seated in the fifth-wheel. *Raise the landing gear of the trailer. Another issue at times: if the trailer was loading from a loading dock using forklifts, it’s probable the rear tandems (the trailer wheels) have been slid to the rear of the trailer. This because a loaded forklift weighs sometimes as much as 15-20,000 pounds. If the tandems were left in travel position they would act like a fulcrum and the entire trailer would teeter-totter. So the driver also has to slide the rear tandems forward into travel position. This gives the tractor/trailer a much shorter wheelbase, thus a smaller turning radius." ], "score": [ 15, 8, 3, 3 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gwk0ke6", "gwk0kj0", "gwk11zx", "gwk0kqu" ], "text": [ "There was a camera attached to the lander already. Kind of like you'd have security cameras outside, or a rear camera on a car.", "There was a TV camera mounted on the lander's leg. It was set to automatically start filming when the ladder was lowered so that it could film the astronauts stepping off the lander.", "There was a TV camera mounted to the side of the lunar module called (appropriately) the [Apollo TV camera.]( URL_0 ) - the footage was broadcast back to earth live. Sadly all the original _highest_ definition NASA tapes were overwritten in the 70s or 80s, so all we have are the lower quality broadcast network tapes that recorded it as it was being rebroadcast.", "Cameras were installed on the outside of the lander. These were thought of beforehand in order to capture the landing and subsequent first steps on the lunar surface." ], "score": [ 17, 14, 6, 4 ], "text_urls": [ [], [], [ "https://en.wikipedia.org/wiki/Apollo_TV_camera" ], [] ] }

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{ "a_id": [ "gwleobx", "gwlfhto", "gwleyqj", "gwlgd1c" ], "text": [ "It would be really hard to push the first gear because the friction of the last gear spinning is multiplied back into the first gear. The reason we use gear ratios is because we trade speed for torque, so if we want the last gear to go fast we need a lot of torque.", "They are essentially the same thing 1:milion and million:1 just means you drive the other end. It would really work in practice, though. There is a simple rule in play, if you multiply the speed, then you divide the torque. This means trying to do the reverse would require so much torque, in practice, that it would simply snap the shaft even if it were made of steel. When you reduce the speed, you multiply the torque, so very little stress is placed on the driving shaft. The other way wouldn't work because even a little friction or resistance on the end would multiply itself to a huge torque required on the driving side.", "Two reasons: * If you're increasing the speed something spins, you're decreasing torque (how hard is it turning, or how hard is it to stop). At some point you'd need an insanely powerful motor, just to overcome the friction at the last gear and make it turn. * Even if you had a motor that powerful, you'd need gears that can survive that torque, and gears that can rotate fast enough without breaking from centrifugal force.", "We don't have an ultra high torque source that spins slow enough to really justify a gear ratio like that, nor do we have materials that can withstand the speeds you'd end up with from the sources we do have. If you start with one of those big cargo ship engines that spins at 90 RPM (1.5x per second) and run it through a 1:625 gear ratio then your output gear is going 56,000 RPM. If your output gear is even 5 cm in diameter then its edges are being accelerated outward at over 88,000x the force of gravity (867 km/s^2) and the teeth are moving at about half the speed of sound, and that's just for 1:625 At around 1:1500 the teeth would be moving faster than the speed of sound in air at sea level. At 1:13,000 you'd start bumping into the speed of sound of steel and your gear would undergo some really interesting failure modes as it is unable to pass the force through itself fast enough. And this is just for a gear 5 cm in diameter, if you pick one that's 25 cm then you hit the speed of sound in steel at just 1:2600 (1/5th the ratio) There is no useful application for a low torque ludicrously fast gearset (there isn't one for a high torque stupid slow one either) and you start running into issues with material properties because you just can't spin the source slow enough. You'd need something spinning once every 12.5 days to be able to match the same gear ratio but in reverse, and you'd need an insane amount of torque on the input and we just don't have something for that" ], "score": [ 7, 6, 5, 3 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gwpzt1b", "gwq099q", "gwq395i" ], "text": [ "Different chip manufacturers have made their chips work in different languages and getting them to agree on a universal machine code is not going to happen. One manufacturer can't take over the world with a single new machine code either. You can think of it like trying to make everyone in the world to only use a single spoken language. Besides, we don't really need a universal language since very few people ever write code in machine languages anyway and we have more universal abstractions. For example, C is basically a universal language that runs pretty much everywhere. A bigger incompatibility issue are the operating systems and more than that the user interfaces but even for them, we have some good solutions using higher level languages like JavaScript.", "Why don't we have one programing language for that matter? Each have their pros and cons, that can change depending on the situation. An embedded system might not need the same optimizations that a regular pc might need.", "Why isn't there a single bolt pattern that is universal for the wheels of all vehicles? Part of it is the vastly different requirements, and part of it is history, inertia, and intellectual property. A cheap microcontroller might use a very simple and easy to implement instruction set with a 4 or 8 bit design, while a processor targeted at high end workstations will be much more complicated, and might include instructions that work on 256 or 512 bits of data at once. Forcing them to converge would be like trying to put the same wheels on a skateboard and a dump truck. As for IP, you can't make an ARM design without licensing it. There are some free ISAs, but they don't have the market share that the big players do." ], "score": [ 10, 4, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gwq9hlv", "gwqdn4o", "gwqgkrr" ], "text": [ "The most important component of electrical transmission, or the process of delivering electricity over long distances, is the [high voltage]( URL_2 ) used. Voltage describes how much electricity wants to move from one point to another. This is very similar to water going into a tank: if the water has a lot of pressure, more will go into the tank. Current is the speed of the water. Now, if the pipe going into the tank were partially blocked so that water could only flow in at a specific rate, the pipe would have some resistance. These three electrical quantities are related by [Ohm’s law]( URL_6 ), which states that voltage is the product of current and resistance. For instance, if we were to block off more of the pipe in the water tank while increasing the speed of the water, pressure would build up. Similarly, increasing either resistance or current increases voltage. Going the other way, if resistance is kept constant by using one type of wire, increasing voltage decreases current. You can see a demonstration of this concept in this [video]( URL_3 ). Power companies use this effect to their advantage for transmission lines and increase the voltage significantly. This voltage “pressure” allows electricity to travel long distances without losing too much energy on the way. Why exactly do higher voltages have to be used? As news site [Inside Energy]( URL_4 ) explains, it’s important to keep current low in transmission lines to minimize power losses. Like the pipes leading to a water tank, transmission lines aren’t perfect and lose some of the electricity they carry. If water is flowing very quickly through a pipe, any leaks will intensify. Similarly, a higher current will cause a transmission line to lose more power. This power loss is a big problem for cables that can stretch hundreds or even thousands of miles. Further, it has a secondary negative effect that can damage the lines: [wasted power is converted to heat]( URL_5 ), which degrades the power lines over time. Power companies perform this step-up of voltage using transformers. These are coils of wire that [increase voltage while decreasing current]( URL_0 ) by the same factor. Even though wall outlets output 120 volts in the U.S. for safety, transmission lines can carry up to [800,000 volts]( URL_1 ). These high voltages are passed through more transformers closer to residential areas for delivery. **TLDR**: They carry high voltages, which reduce power losses and allow transmission over long distances.", "They don't push a lot of electrons through those lines, but they push those electrons CRAZY hard.", "The water analogy of electricity: * Voltage = Electric pressure * Current = water flow (current) * Resistance = resistance to flow High Voltage but low current (similar to a pressure washer) can be dangerous because it easily \"pushes\" a lot of electricity where it isn't supposed to go. Large current (amperage) but low voltage (similar to a flood) can be dangerous because an enormous volume of flow can \"drown\" something it goes into that it's not supposed to. High voltage high current is like a steam pipe and will just vaporize you. Similarly, for a given voltage increasing the resistance will *decrease* the current; for a given current, increasing the resistance will *increase* the voltage pressure. Think of it in terms of water flowing through a pipe with a restriction and it should make intuitive sense. Power is measured in units of Energy per Time - something higher powered can do the same work in less time, like a race car vs a bicycle traveling some long distance. For electrical flow, power is voltage (V) times current (I), the pushing of a current by electrical pressure. Energy can't be created or destroyed just converted between different types, so for a given amount of power (P) the voltage times current (V*I) will be constant. We also know from our analogy earlier that V = I*R (ohms law) so we can substitute that in and get two versions of the equation for power: * P = (V^2 )/R * P = (I^2 )*R This is in an ideal world - in reality, any current will have losses from electrons bouncing against atoms as they flow, the \"friction\" caused by resistance to it flowing, and high current has HUGE losses because of that. Luckily, Voltage doesn't have near the losses because it's just transmitting \"pressure\" with a relatively small flow. So we use high voltage power lines to transmit energy far distances, then use transformers to step them down to lower voltages (240V or 120V) for use. The power remains essentially constant, but we transform between voltage and current depending on which is most useful at that location. Be aware that this is a conceptual approximation, and the water analogy will get you into trouble if you don't remember that it's an analogy. \"All models are wrong; some models are useful.\"" ], "score": [ 80, 28, 6 ], "text_urls": [ [ "https://www.digikey.com/en/blog/what-is-a-transformer-and-how-does-it-work", "https://energyeducation.ca/encyclopedia/Electrical_transmission#cite_note-sec-3", "https://www.azom.com/article.aspx?ArticleID=18258", "https://youtu.be/_eBnz44Nhmw", "http://insideenergy.org/2015/11/06/lost-in-transmission-how-much-electricity-disappears-between-a-power-plant-and-your-plug/", "https://www.allaboutcircuits.com/technical-articles/what-is-joule-heating-producing-heat-with-electric-current/", "https://www.allaboutcircuits.com/textbook/direct-current/chpt-2/voltage-current-resistance-relate/" ], [], [] ] }

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{ "a_id": [ "gwqiy4o", "gwqm282" ], "text": [ "Its made of many glass layers, and within each layer, there is a sort of glue or epoxy that stops the first layer from shattering the next.", "Bullet resistant glass is much thicker than normal glass. And it's usually multiple layers of glass and a plastic film glued together. So you're not just shattering one layer of glass." ], "score": [ 11, 9 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gwuihzc", "gwuip8f" ], "text": [ "> So I was wondering if a Stirling engine could be run and produce electricity from a cold source rather than heat from solar etc Yes. It just needs a difference in temperature, whether this is between ambient temperature and something hot or ambient temperature and something cold doesn't matter. URL_0", "A Stirling engine is running on temperature difference, not heat nor cold. When it's running on the glass of ice water that is just making the room temperature side the warmer side. That's why it runs backwards. It ran slower because the temperature difference is lower between the ice water and room, compared to the hot coffee and room temperature. Also, there is no such thing as a cold source. There is only heat. Cold isn't a \"thing.\" Cold is just the absence of heat. The glass of ice water has lots of heat, just less than the air in the room, or your body, so we call it cold." ], "score": [ 9, 5 ], "text_urls": [ [ "https://youtu.be/O6eEvU5piQg" ], [] ] }

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{ "a_id": [ "gww3wyz" ], "text": [ "An isolation valve allows to to isolate one part of the system. I.e. switch just that part off For examole if you want to change the taps on your sink, you have to take the taps off, which means water will go everywhere when you do. Unless you isolate the sink. Sure you could turn off all the water to the whole house but then nothing would work The isolation valve lets you stop sending water to just one thing at a time." ], "score": [ 8 ], "text_urls": [ [] ] }

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{ "a_id": [ "gwwhpnk", "gwwsqyn", "gwx7ruj", "gwwzf4g" ], "text": [ "There are two plates that can be moved away from each other. One plate is spun by the engine, the other plate is connected to the drive shaft. When you press the pedal in the plates are spread apart and the drive shaft is now disconnected from the engine. When you let the pedal out the plates are pressed together, connecting the drive shaft to the engine. The plate spun by the engine now spins the plate connected to the drive shaft, which spins the drive shaft, which spins the wheels. Think of it like if you set a plate on your table and spin it. While it's spinning, lower another plate onto it. When they are in contact with each other, the top plate will spin.", "For your car to move, the engine needs to make the wheels spin. So there is a strong pipe connecting your engine to the wheels that delivers the spinning motion of your engine to the wheels. This pipe is called a shaft. There is only a limited amount of revolutions per minute (RPM) that your engine can spin, physically, lest it break. But that maximum RPM of the engine is too low to make the wheels spin fast enough to reach the speed we'd like to go at. So, through a complex array of different-size gears (the gearbox), we change the RPM the engine spins at to a larger number of RPM for the tires. In effect, we put a long lever on the side of the engine, and a short lever at the side of the wheels. Unfortunately, while the maximum engine RPM now leads to very fast-spinning wheels, the lever on the engine side is too long to be moved by the torque the engine can put on it when the car is standing still. We need a different lever (gear) for different speeds. To solve this, we put different gears into the gearbox, and to change between them, a stick that lets us move the right gear for the current driving situation into place between the engine and the wheels. There's only one problem left: We need to divide the engine from the wheels in order to be able to change (shift) gears. For this, we split the shaft connecting the engine to the gearbox (and thus the wheels), and put a rough plate at each new end of the split shaft, so that we have two shafts that, when you press the plates onto each other and thus make them stick to each other like velcro, rotate at the same speed. Since they should be connected most times anyway, we just put a strong spring on them that presses them onto each other. The plates and the spring together are the clutch. Now we have a separable shaft and shiftable gears. We just need a way to separate them while driving. For that, we install a third pedal into our car's driver's footwell that, when pressed down, separates the two plates and thus the engine from the wheels. We can now safely change gears. When we then let off the pedal, the spring presses the plates back onto each other. And that's how a manual gear shift works.", "Put your hands gently together in front of you, and keep relaxed. Now, turn your left wrist and forearm back and forth. Your right hand should also move because of the friction between your hands. Now, keep rotating your left hand, and very slowly separate your hands until they're not touching. At some point, your hands were still touching, but slipping. And that's basically how a clutch works. The motor is like your left hand, usually responsible for providing the power. The transmission is like your right hand, and the clutch is the bit where they meet. It's got a spring that tries to make the two press together so the power can go from the motor into the transmission. As you step on the pedal, the clutch assembly separates, letting the two spin independently. As you let the pedal back in, they make contact, slipping at first until the clutch grabs.", "Imagine two flat circles pushed hard against each other. When you spin one, the other spins at the same speed. One is connected to the engine, one to the wheels (almost, for an ELI5). But when you pull them apart, you can change gearing and drop to a lower engine speed, etc. without bringing the wheels immediately down to the same speed. When you press a clutch, the plates are pulled apart, allowing you to safely change the gearing without the engine power transferring directly to the wheels in between (so you don't crunch gears or shoot off at high speed). When you release the clutch (SLOWLY!) the two circles start to match speeds with each other without a huge jolt in speed as they rub against each other. When you completely release the clutch, the circles are pushed together REALLY tightly so they don't slip at all and the engine is basically connected directly to the wheels. Without a clutch, you risk jarring gear changes, damage to gear and engine and axles, etc. With a clutch you can smoothly change between gears, go from 4000rpm down to 1000rpm in the next gear, etc. and then \"ease\" it back into the new speed. It also helps in pulling away because you don't want the (spinning) engine to be joined directly to the (stationary) wheels... either the car will bolt forward, or the engine will stall. With a clutch you can gradually push the circles together without them making full contact and they will match speeds (i.e. the engine speed will drop slightly, and your wheel speed will increase slightly thus you will move off safely and slowly)." ], "score": [ 8, 4, 3, 3 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gwwmcfc" ], "text": [ "It takes more energy to push a windmill forward than you’ll get from the spinning blades. Electric cars do recover some energy under braking, but you can’t generate energy while driving normally - that’s an impossible perpetual motion machine." ], "score": [ 6 ], "text_urls": [ [] ] }

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{ "a_id": [ "gwwptq8", "gwwr2jb", "gwwpqf5" ], "text": [ "It reduces stress on the windows due to pressure changes. The outer layer doesn't have the hole, only the inner layers. There are usually three layers, to protect the people inside from the very, very cold temperature outside. But, if the windows break from the repeated pressure stress, that's also not good.", "The windows are actually 3 layers. A double pane window with a proper seal is on the outside, and then inside is a little plastic window that is easily replaceable. That window is more of a protective layer for the actual window behind it. It does have a small hole in it, and that is because it needs to balance the air pressure and humidity behind it, since it's not fully sealed.", "It helps to balance out the different levels of air pressure. URL_0" ], "score": [ 21, 10, 3 ], "text_urls": [ [], [], [ "https://www.google.com/amp/s/www.businessinsider.com/airplane-windows-tiny-holes-2016-3%3famp" ] ] }

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{ "a_id": [ "gwxap4q" ], "text": [ "They don't necessarily have to know 'where' to dig. You can just start drilling until you hit the water table. So my parents house for instance, the well went 360' before they hit sustainable water. This varies from location to location, and ease of access varies depending on the strata you have to drill through. Their well was 200' of sandstone, then something harder, which makes it pretty expensive to do. Much beyond that depth also requires specialized equipment." ], "score": [ 11 ], "text_urls": [ [] ] }

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{ "a_id": [ "gwy7yaj", "gwy8muu" ], "text": [ "Servos and motors etc aren't as smooth in their motion as muscles are. Some of it is processing power, too. Our brain is far more powerful than electronic sensors etc at detecting very slight motion and adjusting to it (balance).", "> Is it on the programming end, or the hardware end? It's both. The human brain's motor cortex is way more powerful than a typical robot's, and the motors in muscles are built between 10,000 and 1 million times more finely than the motors of a robot." ], "score": [ 7, 5 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gwz0tar", "gwz1iim", "gwz8o97", "gwz5o3r", "gwzec8u", "gwzprbx" ], "text": [ "One obstacle you may already be aware of is that PET has a high melting temperature and releases dangerous fumes when it burns. Also, I’m not a materials science expert but how the plastic bonds with itself when melted is essential. Current 3D printing plastics are used because they form a stable and cohesive structure when layered on itself. It could be possible that PET doesn’t. This is a goodwilled but very ambitious project. It’s a great chance for you to learn but I would talk to a materials science engineer to ensure it’s feasible before committing time and money. /r/AskEngineers may be able to help as the answer to this simply isn’t ELI5.", "Most 3D printers are not to scale to do furniture or playgrounds. There are more efficient ways of recycling the plastic. You basically want to melt it all down and pour/push it into moulds. I’ve seen open source equipment designs for this but have since lost the links.", "You mentioned ocean clean-up. In addition to the challenges the commenters mentioned, you're also going to run into the problem that the majority of the plastic in the ocean is in the form of microplastics. They're very difficult to remove from the ocean water and very difficult to do anything useful with.", "Most important thing is sorting the plastics as they are many types and treating them the same would be like treating aluminum, iron and copper the same. Common plastics like pet (disposable bottles), hdpe (more durable bottles) and ldpe (plastic bags/wrapping) are recycled by washing then melting and extruding. Others like polystyrene (takeout containers) are much harder to recycle and often aren't. 3D printing filament can be very finicky and I believe current recycled filament only uses pet. Unless you/your group have experience in 3D printing I'd recommend sending the plastic to a company that does professional recycling. Finally 3D printers are poorly suited for large objects like you described so I don't think playgrounds are the best idea. But if giving to the community is your goal, 3D printed toys (especially puzzles) can be excellent and can be donated to libraries and schools.", "In my opinion that's one of the most difficult things you could want to do with recycled plastic. 3D printers are pretty picky about the incoming material being consistent (diameter of the filament and purity effecting melting point being big concerns). It's difficult enough to get recycled old prints all made originally from purpose build 3D printer filament. Other methods of pressing or forming the plastic into a smaller variety of shapes would be much more cost effective and reliable.", "I think the profession that could help you is a chemical engineer. Why not just cast the shredded plastic waste into the forms you need? You are starting with random plastics, partially weathered and dirty. You would need to isolate the usable plastics (dispose of what is left), and create an extrudable plastic that is durable and safe. You have to do this chemically or through heat. Perhaps there is a process that will change the various plastics' chemistry to hydrocarbons that could turn be turned into plastics again. ,. You might be able to make an extrudable paste using hardening resins, with shredded plastic as the structural filler. Otherwise, I guess you would have to melt the plastic and blend it using some method to produce consistent stock material. This would be expensive in terms of heating the plastic, and it might produce undesirable gases. The structures being built might have weaknesses from the inconsistencies possible with melted stock" ], "score": [ 9, 6, 4, 4, 3, 3 ], "text_urls": [ [], [], [], [], [], [] ] }

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{ "a_id": [ "gx00lyd", "gx05owv", "gx0n3p9" ], "text": [ "Easiest, though not necessarily entirely correct, simplified explanation I’ve ever heard for torque vs horsepower is this: Torque is the SIZE of the shovel Horsepower is how fast you can shovel with it", "Imagine you are trying to rotate a bolt using a spanner (wrench). If you use a really small spanner you can use one finger to spin it round pretty fast. If you use a really long spanner then you can move a really stiff bolt, but even if it is easy to move you can still only turn it slowly because you have to push a long way per revolution. In both cases you (the engine) can provide the same amount of power, but in the first case you provide high rpm and in the second case high torque. The two spanners are effectively providing gearing between you and the load. This is exactly what gearing does: it trades rpm for torque. Now the situation for boats is slightly different because they are interacting with a fluid. They don't need a clutch like land vehicles do, because the water acts a bit like a clutch. This means it is much easier for boats to generate thrust at zero speed. If I tried to give my car full revs without moving I would rapidly burn out the clutch, but this is fine for a boat (if not particularly helpful). The equivalent of gearing in boats is the choice of propeller; some will give lots of thrust at low speed and some will give low thrust up to much higher speeds. You can build an engine specifically with high torque, but what actually matters is the torque generated after the gearbox at the load (wheels). So the type of engine is less important than the choice of gears.", "The simplest way to describe it is that torque is the rotational force delivered by an engine or motor, whereas power is how quickly that torque can be delivered. Mathematically, power (in a rotating system) is calculated as torque multiplied by the angular velocity. Another way to think of it is that, for a given load, the torque determines how quickly something can accelerate, and power determines its top speed. An important difference here is that an engine or motor does not have to rotate to produce torque, but does have to rotate to produce power. You can produce a lot of torque without producing a lot of power by having an engine capable of producing a lot of force at a low RPM - such engines (ship, truck, train engines) are often heavily built to withstand these forces and as such can't rotate at high speeds, so the amount of power produced is relatively low. These engines are generally designed to move heavy loads at moderate speeds. On the flipside you have engines designed for motorbikes, aeroplanes, sports cars etc. which move lighter loads at higher speeds, so lighter construction and high RPM are more important, and while the torque produced may be relatively low, a lot of power is developed due to the high RPM of the engine. In the case of land vehicles, the characteristics of the engine and gearing are chosen for the application, so a sports car which is light and fast will be designed with an powertrain which prioritises power, while a truck or train which moves heavy loads slowly will be designed with a powertrain which prioritises high torque." ], "score": [ 3, 3, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gx08yo0", "gx08pyo" ], "text": [ "So the wood parts are called ties and the gravel is called ballast. The Ballest works by distributing weight. Push force down on one rock and it will push down the 2 to 4 rockes it is touching. Same thing gor the rocks below. This ends up speading out the weight making it so there are no sinking spots along the tracks As for how the train stays on, the wheels have a lip on the inside allowing the train to fit snugly INSIDE the rails and ont top as well. The wooden TIES tie the rails together by keeping them from spreading apart. They act as keepers to make sure the rails are aligned and won't slip. Rail tracks are actualy quite [bendy]( URL_0 ) Hope this helps!", "A lot of the work keep them on the rails is down to the shape of the wheels which aren't flat but slightly sloped." ], "score": [ 11, 3 ], "text_urls": [ [ "https://youtu.be/MNpUD6iLWNY" ], [] ] }

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{ "a_id": [ "gx2m2we", "gx2m8mn", "gx2ohjh" ], "text": [ "The fewer cylinders, the larger the borehole. That means you have a bigger explosion causing more force to cycle the motor. When you add more cylinders, you have a lot more smaller explosions so the engine cycles quicker at high revolutions as the borehole are smaller/shorter. Big explosions have higher torque while a lot of smaller explosions will create the same amount of power with a quicker turnover for higher speed.", "Torque is cylinder gas pressure divided by cylinder surface area and multiplied by the crank offset (rod journal to main journal distance), with some scaling for angular misalignment in time (liner reciprocating piston versus axially rotating crankshaft means force alignment changes constantly). More cylinders means more weight on the rotating assembly and the torque force is identical (assuming same piston as before, just adding more of them). However, at higher RPM you have twice as many combustion strokes per rotation, which means more power. At low RPM you have a single piston now turning a larger crank with the added weight of another piston's compression stroke added to it. It means less torque per piston. You can tweak things like V angle, cylinder count, firing order, etc. to tailor your engine to the application, and automotive engineers have done a great job of that. But the answer to your question is that typically only one piston is firing at a time in a motorcycle engine and that means the pistons that aren't firing are either exhausting combustion gas, or compressing inlet fuel/air charge. That means some of the torque from the piston currently firing is being used to perform work that *isn't* simply rotating the output.", "Torque is the twisting force. For a single cylinder engine you have one big cylinder that pushes down *really hard* once every two cycles (assuming 4 stroke) and causes the crankshaft to rotate. For a two cylinder you have two slightly smaller cylinders that push down less hard but you get one each cycle. The smaller cylinders pushing down less hard (because there's less fuel/air mixture pushing) means that you get a lower peak torque figure. The trade off is that the single large cylinder has a single large piston, there's a lot of mass moving up and down and you can't throw it around too quickly or you'll start breaking things. Two smaller pistons are each much light and can be revved up higher without over stressing components. Since Power = Torque x RPM (with a scaling factor) the reduction in torque can be made up for by the increase in RPM to get more power in the end Cylinder count vaguely translates into torque vs power, but it really comes down to torque being closely tied to the size of the individual cylinder and power is going to be determined by the torque and how quickly you can spin the engine with bigger cylinders requiring lower rev limits and small cylinders letting the engine spin stupid fast (See F1 1.6L V6s that run at 15,000 RPM)" ], "score": [ 3, 3, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gx34ee0", "gx3595x" ], "text": [ "Most bikes don't. Backpedal brakes have a special hub on the rear wheel. Essentially, the hub has a little internal screw and a bunch of brake shoes. When you pedal backwards, the screw turns and causes the brake shoes to expand, pressing against the inside of the hub and generating friction - which resists the rotation of the wheel.", "Inside the brake mechanism is a screw. You pedal backwards and it turns the screw that pushes The brake pads outward, stopping the bike via friction. See video here URL_0" ], "score": [ 8, 3 ], "text_urls": [ [], [ "https://youtu.be/qKiQplS78dY" ] ] }

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{ "a_id": [ "gx44h8u", "gx46ckk" ], "text": [ "Mechanical batteries are, strictly, any mechanical thing that stores potential energy. Springs, flywheels, etc. they are useful for lots of stuff. Mousetraps are an example of a mechanical battery (a spring in this case) storing the energy needed to swing that trap arm. Flywheels, in particular, are useful as an energy storage system because you can spin them up and use them to power electrical generation. It’s a weighted and carefully balanced wheel that can be spun up to the required high speeds and, if efficient, can even run vehicles. Look up the Swedish “gyrobus” system some time! Electric vehicles, using the flywheels to power generators, and the flywheels can be spun up to speed by machines at the stops or stations, and power the buses from stop to stop.", "I think that you're referring to chemical batteries when you say \"electric battery\". The rest of this post is written under that assumption. There are lots of ways to store energy, then release it later as electricity. Chemical batteries are popular nowsdays for their portability and relatively high energy density, but they have some problems. The chemicals aren't good for the environment (and recharging is only a partial solution). They wear out over time, becoming less and less effective. They're actually relatively heavy for their size, which isn't a problem when they're very small but it limits how large you can make them. *Most* mechanical batteries work at larger scales than chemical batteries. One of the classic examples involves large water tanks at the top of a hill overlooking the river. You charge the batteries by pumping water into the tanks when the river is running high and strong. When the flow ebbs (or at other times when power is scarce), you can release the water slowly, using it to spin electric turbines and generate electricity. You can store and release more energy with this system than you could without chemical batteries, and you can do it without the nasty chemicals. The drawback is that it has to be very large, but you can't really make chemical batteries large enough for this purpose anyway. But mechanical batteries *can* be made smaller, up and to a point. [The GravityLight was an example of this]( URL_0 ). In this case, you charged the battery by lifting a weight: as the weight slowly fell, it would spin a turbine to generate electricity to power the light for 20 minutes. The goal behind this design was cost and robustness: it didn't become less effective over time, and it didn't need new batteries or fuel periodically. The whole system is still larger than a chemical battery, but it could be made \"small enough\". These systems aren't perfect, but neither are chemical batteries. All technology involves trade-offs of some kind, and depending on the situation, sometimes mechanical batteries beat chemical, and sometimes the reverse is true. It's all just a matter of figuring out what works best for the job." ], "score": [ 12, 4 ], "text_urls": [ [], [ "https://deciwatt.global/gravitylight" ] ] }

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{ "a_id": [ "gx45v4l" ], "text": [ "You can. But lenses would either need to get bigger and bigger each stage, or you need to build it slightly more complex with mirrors. There are limits though, you can't see things that are as small as atoms, because the lenses are made from atoms too" ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gx99igb", "gx99tfw", "gx9d0qo", "gx9j7cp", "gx9s6kd", "gx99n3d" ], "text": [ "Yes they relied on two surfaces rubbing together, and yes those surfaces were often greased. A lot (probably the majority) of rotating objects still rely on plain bearings with sliding contact like this. Regarding the resistance, note that the sliding surface is quite a small diameter, and cart wheels tend to be very large. This means that the sliding distance for a given travel distance is quite small, so the effective resistance is quite low. This also helps to reduce wear. Another solution to wear is to make one part sacrificial, often this is a bush or pillow block. This part is made of softer material than the other so wears faster. This can be replaced periodically, and reduces wear on the harder, retained part. Some woods (and plastics) are also self lubricating and so prized for this purpose. For example submarines are or were until recently made with lignum vitae shaft bearings.", "Have you ever tried to set a fire using just friction? It's harder than it seems, and generally wagon wheels spun slowly enough that this wasn't a problem. After that there are two ways to lessen friction. 1. Use a relatively large wheel. Not only does a large wheel help over uneven terrain, but it also means that the inner axle turns slower compared to the distance travelled. Now the larger a wheel is the more weight that you have to put in motion, so you have to strike some sort of balance. But in general large wheels is good. And especially large and light wheels (hence the use of spokes). 2. The use of axle grease. Axle grease is usually some kind of fat that has been thickened (normally using soap) to prevent absorption and prevent it from slipping away. The romans for example supposedly used saponified olive oil (saponified = made into soap/made soap-like). 3. (P.S) And also ball bearings weren't the first kind of bearing. The so called \"plain bearing\" (or specificly for wagons \"bushings\") are ancient. A plain bearing is basically a metal insert that the wheel rotates on. Polished metal on greased wood doesn't generate a lot of friction.", "You've heard the expression \"the sqeaky wheel gets the grease?\"", "Well, to be fair, the earliest most primitive carts show that as the wheel wore a groove in the axle, occasionally youd have to swap-in a new axle. As the hole in the wheel center also wore a bit, the replacement axle would need to be slightly larger in diameter. If you ate any meat along the way, the leftover animal fat could be used as a crude grease to make the joint last longer.", "Unless you're going way back to ancient times then I think the wooden axle would have had an iron bushing over it, and another inside the wood wheel hub. So it would have been much more long lasting and repairable when the bushing was finally worn from the contact. Such bushings are still in use today in all kinds of machinery except they're made of softer metals and they're often lubricated by a constant oil feed to move debris away. This is how the crank and camshafts in IC car engines operate.", "Firstly, most axles would not have spun fast enough for friction to burn them. About how they worked, friction is all about the material. For instance, bronze (which would have been known since ancient times) is a material that is often used in places where you cant avoid friction, but want to keep it low (i dont know the exact material science behind it). Thus, a lot of friction (and thus a lot of wear and tear) can be avoided by choosing the right material. And of course, as you pointed out, adding grease would help as well. Plus, since the average person usually couldnt afford wagons, or even the horse to pull it, carriages would usually have been of high quality anyway, since, if you could afford to buy one, you also had the money to buy a good one." ], "score": [ 49, 17, 4, 3, 3, 3 ], "text_urls": [ [], [], [], [], [], [] ] }

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{ "a_id": [ "gxaa1h4", "gxb52cr", "gxavvl2", "gxag97g" ], "text": [ "Usually they are automatic tire chains. A motor spins them in from if the rear wheels to provide traction without have to stop and put on manual chains.", "i remember learning this at school. theyre hung at the back of the trucks, usually those carrying petroleum products, to transfer any charges (developed on the truck body) that were caused due to friction. it's done to avoid accidents.", "Many trucks have to go over mountain passes. During the winter, water can freeze on the road in the form of either ice or snow, which makes the road more slick. If the road's too slick, it can cause the truck to slide around, which is more likely with big vehicles like those trucks, and can have a bigger impact with those trucks, especially if there are passengers or flammable chemicals on board. Either way, it's really bad if a truck slides around on a road and loses control. In conditions like these, those chains can be wrapped around the tire to improve traction, meaning that the truck will be less likely to slide and grips the road better. However, it does limit the truck's speed, so they're not worn all the time. They're kept on the chassis because the front end of the truck and chassis can be separated, and a different truck can attach to the chassis, but truckers have to make sure that the right chains are being used for that chassis' particular tires. Source: Seen truckers putting up chains in the winter when I went skiing. Though based on other answers, OP might be talking about different chains.", "Overload chains. Meant to stop the suspension from travelling too far away from the frame. Such as when a truck is going through ditches or over railroad tracks." ], "score": [ 27, 15, 12, 4 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gxjchkb", "gxjd1ed", "gxkk9k8" ], "text": [ "In general yes. Depending on exactly what you have to protect against. Water resistant containers will leak a bit in the seams and seals. The higher the water pressure the more they leak. So adding double layer of protection will make sure it takes longer for the water to get through both containers. Similarly fire resistant containers will slowly heat up the inside if the outside is hot. But adding another layer of protection will slow down this process. But of course if someone in transport manages to stab through both containers they will not both be water or fire resistant any more. Similarly if they just scuffed up the outer container the inner container would be infinatly more resistant to water and fire damage then the outside one. So it depends on the circumstances and you may not get exactly double the protection depending on how you measure it.", "Doesn't double it exactly, it will for sure increase the amount of time before the contents being protected is reached though.", "It will generally give you double the rated time at a certain temperature/depth but it will not double the temperature or depth rating itself. e.g. A safe rated for 600 degrees for 30 mins (it will protect your things for 30 mins against a 600 degree fire) inside another safe of the same rating will generally be safe for 60 minutes. This is because the time it takes heat to transfer through double the amount of material is roughly double (not ELI5: steady-state heat conduction is inversely proportional to material thickness). If they were exposed to a temperature of 1200 degress however, both safes would fail almost immediately. This is because the material can not stand temperatures that hot and would melt. You can imagine the same scenario for a safe within a safe both having a 60m depth rating for 30 mins. They could withstand 60m for 60 mins but at 120m your things would get wet immediately. This is because the pressure of the water at that depth is much greater than the material was built to withstand." ], "score": [ 5, 3, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gxk5k70", "gxk70re", "gxk533v", "gxk5fxw", "gxl7w17" ], "text": [ "It is not grounded if you use the meaning connected to the earth. A connection to earth is not required for the electrical system but is a practical way to have a common reference level and possible return part of the electrical system. The frame of ISS will be what is defined as ground ie 0 voltage. This is exactly how it is done in a car where you do not have anything conductive that connects it to the ground.", "Lots of eli12 in this thread. I'll take a stab at lowering that to 5 'grounding' is basically needed to ensure that everything is at the same 'electrical level' (voltage).The hazard of not grounding something is that if the electrical level (voltage) is different in one place compared to another and you touch both, it becomes level by going through you (not good). So as long as everything you touch is all the same level it won't go through you because there is nowhere for it to go. As long as everything in the ISS is all connected to the frame so that it is all the same level (voltage) you are safe. This is why if a utility truck touches a power line and a worker gets out and touches the truck (high level/voltage) and the ground (low level/voltage) at the same time the electricity goes through their body and shocks them badly. If their co-worker JUMPS onto the ground and is never the bridge between the two levels (voltages) at the same time, they will be safe. The important thing isn't dirt, it's that everything is the same 'level' of electrified.", "A ground is an equipotential plane. As long as you understand that voltage is a difference in potential then you quickly understand that the reference ground can be anything. (Doesnt need to be earth).", "The same way parts on aircraft or your car are grounded. Ground doesn't necessarily mean there's a giant spike driven into the ground and things are electrically bonded to it (it does in buildings) it means that's the reference to which voltage is compared with and considered neutral. On aircraft and on cars ground simply means it's electrically bonded to the chassis.", "Everything is connected to the frame of the station, so has an equal reference voltage. Relative to the earth the station could build up a lot of charge. However the ISS also has something called a plasma contactor unit. This allows the station to fire small amounts of charged gaseous ions into space and remove any charge it has built up. This is useful during spacewalks and docking to stop arcing between separate entities." ], "score": [ 97, 33, 12, 7, 3 ], "text_urls": [ [], [], [], [], [] ] }

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{ "a_id": [ "gxl0gr0" ], "text": [ "You car has a centre of gravity - this is the point where you could balance it on a pin. Your car also has a centre of grip. This is the point at which you could push the car sideways and it would move sideways without rotating. When you go around a corner, the mass of the car resists this and you get an outwards \"force\" as you go around the corner which I'm sure you've felt. This force effectively acts at the centre of gravity. If the centre of mass is in front of the centre of gravity, under hard cornering you end up with understeer. This means the car turns less than the amount you've turned the steering wheel. This is pretty easy and feels natural to react to, you just turn the steering wheel a little bit more and everything is fine. If the centre of mass is behind the centre of grip, then you get oversteer. This is quite dangerous unless you're a great driver since the car turns more than the steering input. This means it's very easy to suddenly spin out of control especially during an emergency swerve. Perfectly centering the centre of mass over the centre of grip is ideal, but passenger weight, the amount of stuff in your boot e.t.c means practically it would be very easy to improperly load the car and make it dangerous to drive. So because of this most cars put more weight at the front (engine). Supercars that put the engine at the back are generally really \"mid engined\" as in the engine is towards the middle of the car. They also have huge rear tyres to move the centre of grip backwards. These cars don't have to worry much about cargo or many passengers, so it's easier to align the centre of mass and grip for excellent handling. Edit: this is why a blowout on a rear tyre is more dangerous than a front tyre" ], "score": [ 13 ], "text_urls": [ [] ] }

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{ "a_id": [ "gxniash" ], "text": [ "The problem is due to the fact that tenths cannot be accurately stored in a binary floating point representation. Thus, every number with a decimal contains a bit of rounding error, which typically isn't shown. Typing 0.1 doesn't yield a value that is *precisely* 0.1, and similarly with 0.2 and 0.3, but the error doesn't scale linearly with the size of the number (it honestly doesn't scale at all). E.g. the error in 0.2 is not twice as large as for 0.1 just because 0.2 is twice the size of 0.1. If you want precision, you have to use integers, not floating point numbers, or a specific decimal formatting that gets around this problem. Alternatively, use a programming language that's actually intended for computational work, like FORTRAN or MATLAB or whatever." ], "score": [ 7 ], "text_urls": [ [] ] }

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{ "a_id": [ "gxpo4f5", "gxpnucz", "gxpohxz", "gxpon4q" ], "text": [ "To make sure they work. Theory is all nice and good, but they want to make to make sure it actually works. Going by theory alone is trying to learn to swim by reading a book.", "To make sure that the design works. Nuclear weapons are quite complicated............ except for the one dropped on Hiroshima which was never tested they were so sure that it would work. To test the affects of the weapon. How much radiation? How much fallout? How much blast damage? How far will the blast damage be? And of course to let everyone know that they have nukes.", "How do they know their simulations are correct? A lot of these simulations require that the numbers are calibrated to match the actual physical properties. And these properties might not be the same in an actual nuclear explosion as in very simple lab tests. The US military do have more experience then other militaries with deploying ordinence to combat troops that works on paper and therefore would not need proper testing. For example the WWII era torpedos were expensive and they therefore opted not to test them in live exercizes before the war. The previous generation torpedos had worked admirably and these were just upgraded versions. They were tested and calibrated in specific test locations with dummy explosives so they could be retrieved easily. But as the war became a fact several submarines and torpedo bombers tried in vain to sink Japanese ships without even so much as a glancing blow. The best they could do was to dent the hull of a few of the enemy ships. The problem with the current nuclear test ban is that no country actually know for sure that their bombs actually work if they are called upon. They have done all their simulations, inspections and even dummy tests. But nobody knows if these can actually be trusted.", "In addition to making sure they work, there is also the psychological component (deterrent) of telling other countries they do, in fact, have a working nuclear weapon. Plus simulating a nuclear weapon takes a pretty massive amount of computing and some countries simply can’t afford or have embargoes preventing them from getting that technology legally." ], "score": [ 11, 6, 4, 3 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gxpziy3" ], "text": [ "This is one of the coolest patents I have read. The multifuel engine is based on a diesel engine. The problem with using lighter oils like gasoline and ethanol in a diesel engine is that it will detonate too soon, before the piston is at the top. There are a few changes they have done to prevent this. Firstly there is a mechanism to adjust the injection timing depending on the fuel. This was quite revolutionary at the time using mechanical systems but is now pretty much standard on all engines. But they also use a bit different injectors which does not spray the fuel in such a fine mist but instead coats the hot piston in a film of fuel to evaporate. This makes the injection timings much more similar between different fuels. Another issue is that diesel is its own lubricant so injectors and the fuel pump is actually lubricated by the fuel. So they had to change these to be lubricated by engine oil. The disadvantage to all these changes is that even though the engine can run on all fuels it will run quite badly on every fuel. Fuel consumption is high, it is underpowered for its size and it burns though lots of engine oil. They do run better on diesel then other fuels so this is usually what they use. However the concept is that in an emergency situation where diesel is unavailable they can use other sources of fuel and just mix it into the fuel tank. Especially if the engine is already warm it should be able to run on almost anything. Military vehicles do often have multiple fuel tanks they can switch between and it is a good practice to keep some \"good\" fuel in a seperate tank to make sure the engine is able to start and warm up before switching to the fuel tank with the dirty fuel." ], "score": [ 15 ], "text_urls": [ [] ] }

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{ "a_id": [ "gxseqvq", "gxspwij", "gxssyxi", "gxseq8e" ], "text": [ "Torque is the ability for a vehicle to do work, such as the twisting force applied to the crankshaft. Horsepower is a unit of measurement on how rapidly that vehicle is able to perform that work", "Imagine spinning a roundabout. When the roundabout isn't moving, you can start the roundabout off really quickly with a hard push. That hard push is the torque you apply to the roundabout. When the roundabout is spinning fast you have to move your hand fast as you push. Horsepower tells you how fast you can push. It's the rate you can put energy into the system, how much energy you can add per second to the system.", "Torque * RPM = Horsepower A gearbox exchanges rpm and torque. As a consequence, if the gearing is appropriate, there is little difference between a small, fast engine and and a big, slow one with the same horsepower. Generally, ships, trucks and trains do have high torque but that is almost entirely because heavier, slower motors require less maintenance than light, fast ones. That makes them are preferable where the motor needs to run almost constantly and weight isn't much of an issue. \"Best in Class Torque!\" is a pure marketing gimmick that only means that that vehicle has few other redeeming qualities.", "They have different dimensions: Horse*power* is power: Watts, Joules per second. Or Newton*meter per second Torque is Newtons * meter... and well a quite basic unit so if I'll try to break it down more to ELI5... Torque is \"force over distance\" like turning something around an axis. Horsepower is more generic as energy over time. For instance how much heat is dissipated from an object. Or a more simple example: A heavy crate, say 100kg, is lifted 3 meters up over the time of 5 seconds. The work done equals about 600 Watts (which is the same dimension as HP. 600W is about 0,8 HP). So if one would lift the crate in half the time the power would be doubled. Torque doesn't describe this, it's just the force exerted over a distance at one particular point in time." ], "score": [ 5, 4, 3, 3 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gxt4dej" ], "text": [ "Desalination uses a lot of energy and costs a lot of money build and run the facilities. It would cost so much and use so much power that the cost would make farming using it no longer a profitable venture." ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gxt91br", "gxt7f7h" ], "text": [ "For some reason that has zero scientific merit, people lose their minds at the thought of eating genetically modified foods. Somehow they gained enough political influence for labeling to indicate if their product contains these foods. So at some point in the supply chain the company that makes the yogurt bought a plant or product that has been genetically modified.", "Most likely there is corn syrup in it that originated from corn that has been genetically modified. Whether or not you think that's something to be alarmed about is up to you." ], "score": [ 22, 19 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gxte48i", "gxteebh" ], "text": [ "The primary reason is the human eye and brain has evolved to be able to see more hues of green than any other color. So the minor differences in light intensity the night vision can pick up are clearer to the user.", "A lack of color variety lets us see shapes and details better, this is why some cats and dogs can see much better at night than humans despite being colorblind. Humans can also differentiate more shades of green than any other color, allowing the goggles to provide more details." ], "score": [ 19, 4 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gxvvc92", "gxvvltm", "gxvyb2d" ], "text": [ "Printed Circuit Board (PCB) is the first part of a Printed Circuit Board Assembly (PCBA). A PCB has all the wires connecting various electronic parts printed on one or many layers of the board. It also has metal pads for components to be soldered on. A PCB becomes a PCBA when the electrical components and connectors are soldered onto the boards.", "It's basically just a way to simplify wiring. You can connect two components with wires, but when you have 10 different components (capacitors, processors, ram, fans, etc.), trying to use individual wires to connect all of it gets real messy, real fast. A PCB is basically a piece of plastic with metal lines that act as the wires, but they're not wiggly and tangly. The PCB also lets you clip in components so they all stay in place, rather than a bunch of components thrown into a box that might pull free from their wires if the box gets bumped or turned upside down. \"PCBA stands for Printed Circuit Board Assembly and relates to the component placement onto the bare board or PCB.\" PCBA just means the PCB + the components attached to it.", "Others have adequately answered. Just wanted to add that you'll often see PCB expressed as PWB (printed wiring board) and PCBA expressed as CCA (circuit card assembly). They mean the same thing, just different nomenclature. I've also seen CCA used to describe multiple cards with board-to-board connectors, so like RAM and your motherboard in your PC. That's an assembly of two PCBAs connected directly." ], "score": [ 12, 7, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gxx1oiw", "gxx23r8", "gxx26bz", "gxx12z9" ], "text": [ "Essentially, the RON rating on fuel refers to the resistance to detonation. In a combustion engine you want a controlled burn - one that spreads smoothly from the point of ignition outwards. If the fuel detonates randomly you get something called knocking or pinking, which sounds unpleasant and affects efficiency. Most cars work absolutely fine with the cheapest fuel. This is because the conditions that encourage pre-ignition, mostly high compression, aren't present. The engine computer also monitors for knock effectively by using microphones, and adjusts power and fuel mixes to prevent knock. In very high powered engines fuels with greater resistance to pre-ignition mean the engine can operate efficiently with higher pressure in the air/fuel mix. These cars will still work with standard fuel because the engine computer will suppress performance, but they will be more powerful with higher octane fuel. However, most engines don't operate in ways that take advantage of higher octane fuels. It's like eating out of a bucket rather than a bowl. You can still eat, but you don't get any benefit from it. Eating out of a bucket is only useful if your meal doesn't fit in a bowl.", "It all burns, but at different speeds. Some cars need a faster burn, some cars need a slower burn.", "Not all engines are the same some are made for performance, reliability, economy and consideration is taken for where the engine will run and their fuel quality. Generally the type of fuel is based on the way the vehicle will be used sports/racecar= super specific for best performance owner wants the most out of it, all the way down to agricultural equipment owner wants to pay the least for fuel and get the most out of the engine.", "Not the most scientific answer but basically the octane rating on fuel is how heat resistant the fuel is. When fuel and air go into an engine (cylinder) they are compressed and then a spark is created to ignite them. If the octane rating is too low the fuel may ignite prematurely, which would in turn force the rotation of the engine in the opposite direction and damage the internals. Perhaps a gif of how a 4 stroke cycle works will help visualise that. Hope that helps" ], "score": [ 9, 8, 3, 3 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gxxff8t" ], "text": [ "Laser cutters rely on the laser being focused down into a small point and pulsed quickly to blast away material. If you were to take an unfocused 1000W laser and shine it onto a 1m x 1m hunk of aluminum then you'll get some hot aluminum and nothing exciting happens because the power density is 1000 W/m^2 If you focus that laser down so all 1000W of laser power are focused into a circle that's just 0.5 mm in diameter now you have a laser with a power density of 5 GW/m^2 and the aluminum in the path starts to behave differently. Since focusing down the laser makes it form two cones that touch at the tip when seen from the side, the focal point (where the tips touch) needs to be inside the material for thicker pieces so you can cut all the way through and not just etch the top. The power density is sooo high that the material in the path heats up, melts, and gets blown out of the way by the pressurized gas around the laser before it can transfer much of the heat to the surrounding material. The laser itself just does the melting for the most part, but the machine as a whole can effectively cut through a material with the aid of a laser, thus laser cutting." ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gxx7sul", "gxx7an6" ], "text": [ "The pipeline operational controls weren't hacked, it was all of the ancillary systems. Customer management, orders, logistics, etc. The pipeline was shut down because they couldn't track who was buying what from where and for what price.", "The pipeline functions weren’t attacked, only the company’s main office. They shut down the pipeline while a 3 party investigates." ], "score": [ 18, 5 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gxxc1d6", "gxy9i1v", "gxxgy4o" ], "text": [ "A battery is a device that stores chemical energy and converts it to electrical energy. The chemical reactions in a battery involve the flow of electrons from one material (electrode) to another, through an external circuit. The flow of electrons provides an electric current that can be used to do work. When you connect the battery to a lamp and switch on, chemical reactions start happening. One of the reactions generates positive ions and electrons at the negative electrode. The positive ions flow into the electrolyte, while the electrons flow around the outside circuit to the positive electrode and make the lamp light up on the way. There's a separate chemical reaction happening at the positive electrode, where incoming electrons recombine with ions taken out of the electrolyte, so completing the circuit.", "Because a closed circuit isn't closed in terms of energy. Energy is leaving constantly be it through the hum or heating of the wires, the bulb the circuit is lighting up , the engine its turning, whatever.", "A single battery is actually two things. A material overloaded with electrons and a material that attracts and absorbs electrons. The circuit provides a path for the electrons to go from the negatively charged part of the battery to the positive one. It's basically just pouring energy from one half of the battery to the other, but it does something we want along the way, like pass through a filament and light up a flashlight." ], "score": [ 4, 3, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gxxdka7", "gxxfabq" ], "text": [ "The only question you should be embarrassed to ask is. \"Can I ask stupid question?\" 110v and 120v are so close that they are essentially the same thing. Most electronics in the states are designed to work from ~105v-~135v. Electronics should be labeled with what power they were designed for, often listing it in ranges like \"100-240vac 50-60hz\" I'm assuming you're in the states, common power here is 120v 60hz.", "There is no real world difference. Appliances and tools will run essentially the same off of both. Amps will be your limiting factor. Trailer to trailer,, you should be fine choosing either one.. Think of volts like water pressure, and amps like water volume, and watts like the volume of water flowing through a hose." ], "score": [ 6, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gxxfixh", "gxxex0w", "gxxf6fv" ], "text": [ "Putting diesel in a gasoline engine will lead to the engine not running. Diesel is thicker than gasoline and will clog up the fuel pumps, filters, and fuel injectors. You also can’t ignite diesel with the small spark from the spark plugs. The engine won’t run and you’ll have to purge all the diesel from the fuel system, but there won’t be lasting damage. Gasoline in a Diesel engine is a different matter. Adding gasoline to diesel lowers diesels flash point, making the engine prone to premature detonation and this will cause damage to the engine. The gasoline will also break down more of the lubricants in the Diesel engine, causing more wear and faster failure.", "The engine technologies are completely different. Gasoline engines literally ignite the fuel through a spark, Diesel engines ignite the fuel through compression and heat.", "The fuel ignites at different points, and the engines work in different ways. Diesel won't flash from a spark plug, so it just won't burn in a gas engine. Gas will flash too easily in a diesel engine. So it won't keep a diesel running." ], "score": [ 29, 12, 4 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gxxsfnu", "gxxryu6" ], "text": [ "Space elevators are not standing on the surface but rather tethered to the planet. They are so large that they would extend far enough into space that the pull from space would counter gravity keeping the elevator in a stationary position with no need for it touch the ground. The tethers would keep it stable to a single area as it would be moved by wind or pushed with little effort. The size of space elevator and the material requirements make it impractical to really construct it. Also no know materials could sustain the forces in the middle of the elevator to prevent it from getting ripped in two.", "Gravity is stronger at the surface end, pulling that end to earth. Centripetal force, the force of the earth's rotation, acts to fling the outer end to space. Between the two forces, the space elevator stays \"upright.\" That's the theory, anyway. Currently-known materials aren't strong enough to stand up to the strain, and would tear apart." ], "score": [ 8, 6 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gxxyet2", "gxy0399" ], "text": [ "Wireless network connectivity is greatly impacted by the materials in the walls / Ceiling / floor between you and the device you are connecting to. Basements typically have more metal between you and the outside which can completely kill the signal at the wall.", "Because the signal basically uses line-of-sight. Inside a building, you may have a few inches to a couple feet of stuff besides air between you and the tower, even several rooms deep inside. Meanwhile, being even a few feet below ground, that could change to tens to hundreds of feet of earth, which is full of various metals and such that are great at disrupting and blocking the signal." ], "score": [ 6, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gxy3v18", "gxy560n", "gxy91ym" ], "text": [ "Every molecule of fuel burns a certain amount of oxygen, and releases a certain amount of energy as it does. It's easy to add a lot of fuel to the cylinder, so much fuel there isn't enough oxygen to burn it all. A turbo is just an air compressor that squeezes more oxygen into the engine so you can burn more fuel and release more energy, making the engine more powerful. The difference between a turbocharger and supercharger is that the turbocharger is driven by exhaust gas spinning up a turbine, and a supercharger is driven by a belt or gears directly by the engine.", "There are two aspects to a car's engine. Its torque, and its speed. An engine which spins faster can generate more nyoom, even if the force of the engine is no higher. This is due to the magic of gears. However, for turbos, the speed of the engine does not get any higher, so all we care about is the force inside of the cylinders; the force on the pistons. This force is generated by the explosion of gasoline and air within the tubular cylinders. If you want more force, you add more gas, until you run out of air for that gas to burn with. If you keep adding gas at this point, you're basically just dumping it straight out the exhaust unburned. So, how do we fit more air into the cylinder? We *could* make the cylinder bigger, but that would require a whole new engine block and all sorts of other modifications. What if, instead, we squished the air down so we could fit more of it into the same amount of space? That way, we can burn more gas and apply more force on the pistons without actually making the engine any bigger. This is what both turbochargers and superchargers do. Superchargers use an air compressor driven directly by the engine. Turbochargers use a compressor powered by the motion of the engine exhaust - both have their own advantages and disadvantages.", "So to start with - the most basic point is - an engine goes faster (or produces more power and torque) if it burns more fuel. So if you keep the engine size (combustion chamber size) the same - the only way to burn more fuel is if we force feed it with more fuel. But only fuel does not burn - it needs air (oxygen) also - hence we need to force feed it with air also. The former is done by fuel injectors and the latter by the turbocharger / supercharger. A turbo just pushes more air into the engine and with the extra fuel being injected by the injectors - the engine burns more fuel producing more power / torque and runs faster." ], "score": [ 17, 10, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gy0ucg1", "gy1cq5e", "gy1mr30", "gy3tlva" ], "text": [ "Red lights at night save your night vision. If you turn on a regular light, it can take an extended period of time for your eyes to refocus when you shut it off. That’s not the case when using red lighting.", "I was a navigator in the U.S. Navy for a few years. I had to read charts (maps), write in logs, and read stuff on the bridge lit in only red lighting. Took awhile to get used to, for sure. My initial assumption was that we wanted the ship to remain as dark as possible from potential threats, which is partially the case. And as others have mentioned, red light is much easier for your eyes to adjust to in nighttime conditions. Our chart room/office/haven was normally lit, and going in there from red light would nearly blind me, and walking out into red light took *several* minutes to adjust.", "Same reason pirates used to wear eye patches. The lighting from above deck and below deck are often so different that you need to preserve your ability to see in the dark some how. For \"pirates\" it was just keeping one eye always in the dark.", "Merchant navigator here (major container ship carrier), as other says, the red light is a night vision saver and is also often also more dim then the regular white light... BUT there are problems with it: More and more new tech on the bridge, all to be dimmed every morning and evening manually. Some with shit dimmers so you end up covering them instead (non critical equipment). A classic is the toilet, switch on the door so when you open, the red light goes on, but when you are inside and door closed, the white light is back on (I always make the \"pirate\" when going out there ie. closing the one eye) Other annoying light are typically power indicators, bright and undimmely" ], "score": [ 60, 10, 5, 3 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gy1o4js", "gy1cbqf", "gy1a14s" ], "text": [ "There seems to be some confusion in the responses between a wing and a spoiler. A wing, like F1 cars have, is basically an upside down airplane wing, that pushes the car into the ground. At legal highway speeds, a wing has little to no effect. A spoiler is different however. It is used to break up airflow. They are very useful for reducing drag and increasing fuel efficiency. Many cars will have a front spoiler to reduce the amount of air going under the car. Rear spoilers can reduce the low pressure behind the car. You will often see cars with rather flat rears have spoilers to make the rear of the car appear more sloped to the air. Famously, the Audi TT was released without a spoiler. After a number of accidents, it was recalled and a spoiler was added: URL_0", "Spoilers on commuters cars have an entirely different reason than racecars. They dont exist to create downforce, they exist to spoil areas of low pressure that cause drag. When the flow is smooth this is usually a good thing. This is called \"laminar flow\". But on the back of the car the smooth flow causes low pressure as the air goes over the back edge of the vehicle. The spoiler is there to ruin this airflow and reduce the low pressure causing drag on the tail. Thats why the spoilers are shaped differently on commuter cars.", "Spoilers provide downforce at highway speeds. The downforce helps the car stick to the ground, especially in turns. How much depends on many factors. Indy cars provide enough downforce that at race speeds they could literally drive on the roof of a tunnel. On small commuter cars the downforce is still there and helps at highway speeds. But overall the total performance of the car suffers, albeit an imperceptible amount. This is because it adds more drag to the vehicle. More drag equals less gas mileage and performance. And for you speed junkies out there. A big spoiler on a fwd car will most definitely slow you in the quarter mile, and in extreme cases can cause your front wheels to loose grip under high acceleration/high speed situations. The back end of the car is being pushed down which pushes the front end up. This is because these cars were not designed for this. High performance cars have other aero components to put downforce in the front as well." ], "score": [ 23, 8, 4 ], "text_urls": [ [ "https://drivetribe.com/p/remember-that-time-audi-recalled-Ox5qolemROy6BeZrfPa1xw?iid=P20PDsviSJCiWNryxJTFAw" ], [], [] ] }

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{ "a_id": [ "gy1gmvf", "gy1h0zo", "gy1h2zl", "gy1iu2d", "gy1s057", "gy2ujbq", "gy1m1ty", "gy1m0k0" ], "text": [ "Long pieces of plastic which are strong enough to support a house are pretty expensive and heavy; it's easier and cheaper to build a wood frame and then wrap the whole structure in thin layers of waterproof plastic + other waterproof materials to keep everything dry.", "It might not biodegrade but it does degrade. Especially many plastics are extremely susceptible to UV, going weak and brittle in comparatively little time.", "Structural plastic is softer (weaker) and more expensive (or at least it was until the recent lumber shortage), and it's also susceptible to damage from UV rays in sunlight (plastic exposed to sunlight will become brittle and crack and break). Plastic with additives to deal with the UV are even more expensive. We do use a lot of plastic in home construction, just not structurally. Plastic sheeting for moisture barrier, plastic water pipes, plastic (or more accurately polymer) electrical junction boxes, plastic (polymer) wire insulation, kitchen cabinet veneers are sometimes made of plastics, etc.", "Plastic is not biodegradable but it is not particularly strong not it isolates heat very well. Also, since it is not biodegradable, it would make ecological catastrophe.", "Plastic degrades when exposed to UV light, which a building would be. Plastic also doesn't like to hold up to consistent loading; even a slight weight, applied for a long time, will cause plastic to sag. That said, a lot of a building is plastic: the vinyl siding and flooring, the moisture barriers, the glues inside engineered lumber, the insulation; just not the structural elements.", "If it's kept dry, wood will last centuries. And actually gets stronger with age. Plastic would be worse for the environment, a lot more expensive, harder to work with and doesn't perform very well structurally. There's really no reason it would ever be used for that purpose.", "Wood is cheaper. That is all. You could make plastic equivalents to the structural timber used for houses but lengths of 4-by-2 are amazingly cheap. Plastic replacements would have issues to overcome but you can be that, if there was money in it, the industry would find a way. Two that occur to me are that: nailing plastic wouldn't work well and you'd need to change the fixing systems used; and sunlight kills plastic so you'd have to take care to make sure it didn't penetrate to strutural members. Of course using plastic to replace wood would be an environmental disaster but that factor still loses out economics. There's a huge amount of plastic already used in home construction. My house is clad with foamed polystyrene 4\" thick.", "It should be noted that wood used in the construction of houses is treated to make it harder to biodegrade. It may also be protected with a varnish or polycoat if it will be exposed to the elements. The vast majority of wood in a home will *not* be exposed to elements beyond some humidity. There's also not a whole lot of organisms that are good at destroying and decomposing wood that don't require a ton of moisture (like fungi) and usually aren't immediately dangerous as long as you take care of your home even a little bit. Homeowners go through a lot of trouble to prevent the ones that *are* immediately dangerous (like termites) from getting into the home. Houses can survive even pretty substantial natural disasters like flooding and still remain structurally sound. There are centuries-old houses with the original wood structure that are still standing today. The biodegradability of wood just isn't a concern when it comes to making houses out of the stuff, provided you take care of it properly. On the other hand, wood is cheap (current shortage notwithstanding), pretty lightweight, flexible, easy to cut, often aesthetically appealing, sustainable (when properly managed), and ubiquitous in many countries. There's no reason *not* to use wood framing when it's available and affordable." ], "score": [ 45, 37, 10, 9, 4, 3, 3, 3 ], "text_urls": [ [], [], [], [], [], [], [], [] ] }

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{ "a_id": [ "gy6j6pw" ], "text": [ "When you blow on a fan, it spins. If you put one fan in front of another fan, and spin one of them, the moving air will spin the other. If the other is held still, it will still experience a force from the spinning of the first one. If you replace the air with oil, the force transmitted is much higher. If you enclose the whole thing and shape the fans so that the air blowing past the 'output' fan gets recycled into the 'input' fan, you get a much more efficient system - the air doesn't have to come to a stop and so the energy of its motion can be reused. This is the physics behind the torque converter. This final step, of shaping the blades and casing to recycle the moving oil at maximal efficiency, is why the inside of a torque converter looks very little like the fans we started with." ], "score": [ 10 ], "text_urls": [ [] ] }

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{ "a_id": [ "gy6rkft", "gy6u0hw", "gy7am9s" ], "text": [ "“The CO2 breathed by astronauts aboard the ISS is captured by using a sponge-like mineral called a zeolite, which has tiny pores to lock in a CO2 molecule. On the space station, the zeolites empty their CO2 when exposed to the vacuum of space.” Source: URL_0", "On the ISS, filters containing a mineral called zeolite capture the CO2 and then when the filters get full, they're exposed to the vacuum of space which removes the CO2 and the filters are used again. In space suits and in the spacecraft that bring astronauts to and from the station, non-reusable lithium hydroxide filters are used.", "How do they assure the supply with O2 though? Is it just shipped up constantly as a gas or do they get it from another source or something?" ], "score": [ 17, 5, 3 ], "text_urls": [ [ "https://phys.org/news/2018-11-space-station-astronaut-exhalations-earth-based.html" ], [], [] ] }

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{ "a_id": [ "gy7ewpj", "gy7iodf" ], "text": [ "Safety and cost. They are very expensive to run and electricity from the grid is much cheaper. And the risk to the population is much greater in a town than on a ship out at sea.", "Application and security Nuclear reactors run hot, heat steam, ram it through a turbine, then cool it down again. Naval reactors are surrounded by an infinite ideal heatsink (the ocean) so they don't need to waste space on a big cooling tower. There's also scale. The new Gerald R Ford class of carriers has 2 700 MWth reactors. Three Mile Island unit 1 generates 800 MWe or about 2400 MWth just as a single unit. Sub reactors are even smaller with new ones being in the 200-300 range There's also that big problem with security Sub reactors need high power density so they're fueled with highly enriched uranium. Land based reactors generally use 3-5% which is very far away from what you could turn into a bomb. Submarines need to be compact so their fuel is over 50% enriched. Part of the reason for 5% being the limit for commercial reactors is because it's soo hard to go from 5% to 90%, but 50% is already most of the way there" ], "score": [ 5, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gy87rek", "gy87vba", "gy885lk", "gy8a9or", "gy8hhq8" ], "text": [ "Small planes often do carry a large parachute for the entire plane. Larger planes are too fast and heavy for this to be practical, and typically crash during takeoff and landing when it wouldn’t help anyway. Big aircraft also have multiple engines, and can continue to fly to the nearest airport in the event of an engine failure. Mid-flight cruising crashes are extremely rare even among already-rare large plane crashes.", "There are such systems for small airplanes: URL_0 For big ones, the parachute required would just be too large and too heavy. Also, most airplane accidents don't happen in midair, but on takeoff or landing, where a parachute wouldn't have enough time to inflate.", "A parachute large enough to \"safely\" decelerate a plane would be extremely cumbersome to install, maintain, and carry. Many times when things go wrong with the plane, it can still glide. Catastrophic plane crashes are usually in situations where a parachute won't help either. If a plane loses engines a few seconds after takeoff, there's not enough altitude for the parachute to deploy before the plane hits the ground again. If the plane loses control when landing, it's the same problem. Instrumentation errors means that the pilots don't know they're flying into a mountain/the ocean, so they wouldn't think to deploy the parachutes anyway. A parachute is only really useful if the plane has a catastrophic, structural failure, like a wing falling off. These kinds of things are much less common than other failures, because the strength/structure of the wing is (relatively) simple matter, compared to the control and power systems of the plane and pilot training.", "Planes almost never need something like this. Smaller planes operated by less expert people might need it more, and such systems exist for those planes. Commercial passenger planes are the most safe thing you wee in day-to-day life, a parachute wouldn't make then measurably safer.", "Not a practical solution… most crashes are at takeoff or landing, where there isn’t enough height to deploy and slow a falling aircraft. And most commercial flight failures in mid-air are explosions, as planes can fly on a single engine if they lose one. A stall leading to a crash is mostly a small, single plane issue." ], "score": [ 15, 14, 4, 3, 3 ], "text_urls": [ [], [ "https://en.wikipedia.org/wiki/Cirrus_Airframe_Parachute_System" ], [], [], [] ] }

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{ "a_id": [ "gy8w3pl", "gy8vmy2" ], "text": [ "One way Glass isn't really a thing. What you do is have the room you want the observer in much darker than the room the observed is in. The light from the observers room is dim enough to be washed out by the reflections of the lit room thus all people see in the well lit room is there own reflections, meanwhile the light from the observed room greatly overpowers the reflection from the observers room, allowing for easy viewing. You can try this yourself if you have a window or a glass door near a light fixture. Wait until it's night, turn on the light and try to look out the window without leaning against it. Chances are you will see nothing but a reflection. Go outside and then look in. You'll be able to see everything in perfect detail. That's basically how \"One way glass\" works, it's all trickery of light and reflection. There's nothing special about the glass other than maybe one side being polished to amplify the effect.", "From the wikipedia article: > A one-way mirror, also called two-way mirror[1] (or one-way glass, half-silvered mirror, and semi-transparent mirror), is a reciprocal mirror that appears reflective on one side and transparent at the other. The perception of one-way transmission is achieved when one side of the mirror is brightly lit and the other side is dark. This allows viewing from the darkened side but not vice versa. > The glass is coated with, or has been encased within, a thin and almost-transparent layer of metal (window film usually containing aluminium). The result is a mirrored surface that reflects some light and is penetrated by the rest. Light always passes equally in both directions. However, when one side is brightly lit and the other kept dark, the darker side becomes difficult to see from the brightly lit side because it is masked by the much brighter reflection of the lit side.[4] This is analogous to being in your house at night with the inside lights on and being unable to see someone outside, whereas they'd be able to see you perfectly." ], "score": [ 9, 9 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gy9xblg" ], "text": [ "There is multiple way but the general idea is to have equipment along the rail that detect the train. It has to be done at the appropriate distance so the the light have time to blink, gates closing etc. A device that detect trans is called a [Track\\_circuit]( URL_0 ) The simple way is to have have isolated gaps in the rails so not electricity can pass along the rails.You then have a electrical circuit that with a connection to each rail and when the steel wheels of the train roll onto the track they create a short and you have a electrical current between the track. Now you have a signal that tells a train is on the track and you can activate the crossing So you use the two rails and the train wheels as a large eclectically switch. There is more advanced circuits that you use if it is a electrical train and the rails is used and one connector or if the system should handle trains with large speed difference so there is not unnecessary long blocking of the lines for slow trains." ], "score": [ 5 ], "text_urls": [ [ "https://en.wikipedia.org/wiki/Track_circuit" ] ] }

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{ "a_id": [ "gybbgxm", "gybb513", "gybgrvn" ], "text": [ "They exist in commercial kitchens and are called blast chillers. They're incredibly expensive to run and quite large and heavy - the physics of making things cold is far more energy intensive than heating them up. Additionally, household demand for cooling just doesn't exist to any great extent - most people don't cook batch products like commercial kitchens, so they can be cooled in a normal way (spread out over a larger surface area and then transferred to the fridge) without being in the danger temp zone for too long, and anyway, most people aren't as concerned about food hygiene at home as a professional kitchen would be. At best, the demand might be to get your beers cool fast, but a soggy paper towel round them in the freezer generally does the job. Ultimately, all these elements mean that it wouldn't be commercially viable to bring them to market as domestic appliances.", "You can put it in the fridge or freezer depending how hot it is and how quickly you need it cooled?", "When you heat things up, you can apply a very strong heat difference. For instance, when you boil an egg, you put it in water that is about 75-100 deg. centigrade hotter than the egg's original temperature. That's gonna heat the egg pretty quickly. Or when you bake something in an oven, it's not hard to get a temperature differential of more than 200 centigrade. Again, that's gonna raise the temperature of your dish rather fast. If you could put something in a -200 degree freezer, it would cool down pretty quickly too. Trouble is, it's hard to make a freezer that cold. Your fridge runs at about 4 centigrade, and home freezers go to maybe -20. Expensive medical-grade freezers (e.g. the ones used for some of the corona-vaccines) might go down to below -70, and it's possible to go even colder but it gets harder and more expensive. Basically, lots of simple chemical reactions (e.g. burning) and physical processes (e.g. running electricity through a wire) generate heat, whereas drawing heat away is a much less \"natural\" process. You definitely can speed the cooling process up though, even with the small temperature gradients that are available in home settings. Let's say you're wanting to cool down a can of soda. One thing that will really help is to immerse the can in ice water, since water is a much better heat conductor than air. If you can keep the water moving around, that helps too, as this will replace water that's been warmed by the can with colder water. So in theory, you could make an ice-water-circulator appliance for quickly cooling down drinks. The demand for such a product would be very small, though, as you can achieve a very similar effect with some ice cubes and a bucket when the need arises, and most of the time you can just avoid this issue completely by storing your drinks in the fridge ahead of time. It's also not clear how to make this a particularly convenient product, unless it's hooked up to a water source as well as a water drainage system (otherwise it's not really better than a bucket, only with some kind of fan or pump to keep the water moving automatically)." ], "score": [ 34, 4, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gycggo0" ], "text": [ "The difference in sound quality you hear from different sources is called [*timbre*]( URL_0 ) (pronounced \"tam-ber\")." ], "score": [ 6 ], "text_urls": [ [ "https://en.m.wikipedia.org/wiki/Timbre" ] ] }

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{ "a_id": [ "gycc3i5" ], "text": [ "Mars is a long way away, so they don't have good 5G coverage. If you take high resolution pictures, like the New Horizons spaceship to Pluto took, then it takes months to get them back to Earth. If you want video to show in real time on TV, then you're stuck with low resolution and low update rate." ], "score": [ 4 ], "text_urls": [ [] ] }

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{ "a_id": [ "gyg3ew4", "gyg3sh5" ], "text": [ "Sometimes it is flickering because of poor contact with the terminals touching the globe. By knocking it, there is a chance that the fixture makes better contact therefore eliminating the flickering. There is an equal chance that knocking it removes the contact altogether which results in the light not working at all.", "Sometimes the problem is a bad connection and tapping it can fix it. Several elements of the system are essentially metal plates making contact so power can flow from the light socket to the bulb filament. If that contact is weak, or if there is something in the way like dirt or corrosion, the bulb could flicker." ], "score": [ 6, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gyid60s", "gyie92l" ], "text": [ "The RPM measures the engine rotations, not the transmission. But the RPM goes lower because you are going at a speed, lets say 30MPH, and change from lets say 2nd gear into 3rd gear, which is geared higher. So initially, to stay at the same speed, your engine has lower RPMs to be at 30MPH in 3rd gear than it had in 2nd gear. Of course, you can step on the gas to go back up to the same RPM you had before, but you'll be going faster. The input RPM is not fully independent of the gear ratio. Since the power goes through the transmission and ends up in your drive wheels, the RPM of the engine does depend on gear ratio. The wheels will turn faster at higher gears.", "The engine is connected to the transmission directly. The engine flywheel and the transmission input shaft spin at the same speed. In a manual transmission when you change gear the clutch disconnects the engine from the transmission then reconnects the engine to the transmission. This disconnection will result in engine speed falling if you don’t keep your foot on the accelerator. When you change the gear ratio the engine must lower its RPM to match the transmission speed for the wheel speed in the new longer gear ratio. Imagine if you will: an engine at 1000rpm in 1st gear with 1:1 gear ratio going 1 mile per hour. The transmission and the engine are both spinning 1000 rpm to go 1 mile per hour at the transmission output shaft. If I change gears to 2nd gear at 1:0.5 gear ratio the transmission outputshaft will now be going 500 rpm to move the car at 1 mile per hour. Thus I have to reduce my engine speed to 500rpm to maintain the 1:1 ration at the engine to transmission connection." ], "score": [ 9, 4 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gyiu644", "gyj00to" ], "text": [ "They're just painted plastic or aluminum covers for the lug nuts holding the front wheels. As for purpose, they may protect against some corrosion but they are mainly an aesthetic statement by the driver that doesn't go against the policy of the company hiring the driver.", "copied from quora It is simple. Tl:dr - the front wheels and the back wheels are identical, but the front wheels only have the “inner tire”, so the lugs are protruding, where the rear axles have the outer tire installed, covering the lugs up. In order to carry the loads that we carry, many years ago engineers decided that they needed to be able to have 2 tires in a pair on the end of an axle, and so they designed the Dual Wheel. It is a wheel with enough “Offset” (the distance between the face of the tire and the mounting surface of the rim) that the mounting surface ends up next to the tire instead of inside the tire. This allows 2 tires to be put on together with one set of lugs and studs, while keeping a little bit of space between the tires, by having one rim reversed in comparison to the other one. The front end of the truck doesn't carry as much weight (around 12,000 pounds on the front axle, and around 17,000 pounds on each rear or trailer axle, for your normal 5 axle semi in most states), and so it can get by with only a single tire, (and there is really no practical or safe way to have dual tires on the steer axle anyway), and the natural way was to use the same rims as all the rest of the axles, so basically the front wheels are installed just like the inner wheels on the rear axle, with the dish out, and other than looking funny compared to many cars,(Though many cars also have dished out wheels, to give them more space inside for brakes and such) they look perfectly normal among any dual wheeled vehicle!" ], "score": [ 11, 8 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gyj1hbm", "gyj1tbg" ], "text": [ "For the most part things change temperature when they touch other things. If you had a drink that was 70 degrees inside a room where the air was 70 degrees they would both just stay 70 degrees. If the drink was hotter than the air it would it would transfer its heat to the air and become cooler. If the drink was colder than the air, the air would transfer it's heat to the drink and the drink would become warmer. If you could suck all the air out of a room the drink would just stay the same temperature since nothing is taking it's heat away or adding to it (not entirely true). A lot of mugs actually have an inner wall and outer wall with a vacuum in-between to create this effect. Now obviously the inner wall is connected to the outer wall at some point to hold the mug together. Additionally things will radiate heat even if they're not coming into direct contact with anything. So mugs won't keep things hot (or cold) forever, but it can last a while.", "The gap between the inner layer and the outer layer greatly reduces heat transfer, so the heat from hot beverage has a hard time leaving, and a cold beverage is protected from outside heat coming in. The gap is either a vacuum or filled with an insulating material, like foam. A vacuum is a very good insulator because there's nothing to transmit the heat. You'll notice that when you hold a thermos, the temperature doesn't match what's inside. Items cool by radiating heat or conducting heat through a conductive material, like metal. That's why metal spoons get hot if you leave them in a cup of coffee. Similarly, items warm up by absorbing radiated heat or receiving conducted heat through a conductive material. That's why metal ice cream scoops get so cold." ], "score": [ 7, 4 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gyjddmi", "gyjdyu1", "gyjdqkl" ], "text": [ "Huge tanks are suspended in the air so that gravity drives the water downward. These are water towers. The tanks are periodically replenished by pumps, but beyond that they supply all the necessary pressure with gravity. If a large enough leak formed in your pipe - large enough to lose a significant portion of all of the water flowing through the mains pipe - then your neighbor could lose pressure.", "The city water system is pressurized and carried in large pipes. Most often, that’s what’s water towers are doing; they provide the pressure for city water (though there are other ways to do this). Those mains are large enough to serve whole neighborhoods worth of average consumption without losing much pressure. Your typical 1” house main is tiny compared to the 8-10” main that it connects to at the street.", "For a normal residence, water pipes do not get their pressure from any electricity in your house. If your power goes out you will still have water pressure. They are pressurized because the pipes they receive water from (the water mains) are pressurized from the cities water source. When you turn on your faucet, that water main (which is pressurized) sends water through the pipe in your house to your faucet. If you get a leak (or if you turn on your faucet), some pressure is lost from the water main since it has to send some of its water through your pipes to the point of exit. Although it is so tiny, and the water main is constantly being flooded with more water to keep its pressure up, it won't really make a noticeable difference. Within your house you may notice a dip in water pressure however if there are two water uses going at once. For example if you have the shower running and flush your toilet, you may notice your shower's water pressure drop. This is because only so much water can be sent from the water main into your house's pipes. When it reaches your house it has to branch off to all the 'exits' that are open (the shower and toilet). So it has to split the pressure between the two. Here is a great video on the topic: URL_0" ], "score": [ 6, 6, 3 ], "text_urls": [ [], [], [ "https://www.youtube.com/watch?v=ZQKpu-obzlU" ] ] }

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{ "a_id": [ "gypx6nc" ], "text": [ "There used to be all sorts of different shift patterns, and this became a safety issue when drivers got behind the wheel of a different vehicle and used the wrong selection. So eventually the US government [passed a law]( URL_0 ) standardizing on Park-Reverse-Neutral-Drive-Low." ], "score": [ 8 ], "text_urls": [ [ "https://jalopnik.com/why-prndl-5870701" ] ] }

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{ "a_id": [ "gyqj755", "gyql3vy", "gyqj8ap", "gyql9av" ], "text": [ "Generally just a die stamp where they press/form the desired metal blanks into the proper shape using a harder thicker die and several tons of pressure. [Here's a video of how it's made]( URL_0 )", "Like /u/Bloodyneck92 and /u/KahBhume said, you can build it right in.But, if you need to make a non-circular hole in something after it's been formed, you do an operation called \"broaching\". You basically have a specialty cutting tool that, rather than spinning like a drill bit, is pulled through the piece and steps up in size/shape until you get the size/shape you want. [ URL_0 ]( URL_1 )", "A couple ways. Parts could be die-cast. That is, liquid metal is put into a mold which hardens into the desired shape or heavy presses physically press the metal into shape. Holes can also be cut into various shapes using specialized saws and grinders.", "There are a few ways of doing it depending on the material and shape. You can punch it, file it, mill it, cast it, or a combination of different techniques. One of the coolest techniques however is broaching. First you drill out most of the material using a regular drill. They often use an oversized drill making the walls of the final hole rounded from the drill bit which is normally fine and is a nice tell of how they made it. Then they push a square or hexagonal broach through the hole to cut out the corners. If it is a through hole they can push a broach through with multiple cutting surfaces, the first ones the same size as the initial round hole and then they become more and more square or hexagonal until the final cutting surface being the final shape. If it is a blind hole so you can not push a long broach through you need a rotary broach. The setup often seam very complicated with offset bearings and compound tools in a lathe or drill press but it is essentially quite simple. The broach have cutting surfaces around its edge in the shape of the final square or hexagonal shape. It is then pushed through the material but the tool will make sure to wobble the broach around so that it cuts a tiny bit of the material off for each wobble." ], "score": [ 12, 8, 3, 3 ], "text_urls": [ [ "https://youtu.be/RtcYB-mW6i0" ], [ "https://en.wikipedia.org/wiki/Broaching\\_(metalworking)", "https://en.wikipedia.org/wiki/Broaching_(metalworking)" ], [], [] ] }

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{ "a_id": [ "gyr0yk8", "gyr1zq0", "gyr1pqx" ], "text": [ "Aviators weather reports will provide anticipated wind speed and direction at different altitudes, so to some extent you can control which prevailing wind you are in by changing altitude. In general though, you are entirely at the mercy of the wind, so ballon journeys are hops in a single direction planned in advance in accordance with the wind direction.", "They aren't, they go wherever the wind blows. They can control their altitude but they cannot control their direction. Hot air balloons will often have a chase car that follows them wherever they go to be ready to pick the balloonists and their balloon up when it lands.", "You need a good knowledge of meteorology so you can make observations and predict the way the winds travel at different altitudes. A lot of times wind might go around mountains and other terrain features or you might have different air layers with different winds so the air can move in different directions at different altitudes. An experienced balloon pilot will be able to predict these different winds or just experiment though them and find the right altitude where the winds take him where he needs to go. But if you are under the impression that a hot air balloon can travel in any direction the pilot wants you are mistaken. The level of control is enough to land it safely but in order to get where you are going you need to pay attention to the weather forecast beforehand and pick a take off spot carefully so that the wind actually take you there. But this is perfectly fine for sight seeing tours and such." ], "score": [ 28, 4, 4 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gyuyj54" ], "text": [ "It's not. There's a bunch of things going on here, but a propeller is significantly more efficient than other ways of creating thrust. That's why wind turbines look like giant propellers. A turbine does not create thrust (\"wind force\" in your question). But definition, a turbine takes energy \\*out\\* of a moving fluid. Things that make thrust are putting energy \\*in\\* to the fluid. We call those propellers or fans; there's no rigorous definition difference, although in aviation \"propeller\" means \"thing without a shroud\" and \"fan\" means \"thing with a shroud.\" \\*If\\* you don't have a speed constraint, a propeller is the most efficient way to add energy to a fluid. That's why small aircraft, commercial turboprops, and boats all use propellers. They don't go fast enough to run into the speed problem. Commercial & military jets, however, go so fast that the efficiency of propellers drops way off because they start getting near supersonic speeds. That's why they use fans instead. You have to be going a couple of hundred miles an hour, at least, before this becomes an issue. Since that \"never\" happens with wind turbines, they also don't have to deal with the speed issue and they use a design that looks a lot like propeller. It's a turbine, not a propeller, because it's taking energy \\*out\\* of the fluid." ], "score": [ 9 ], "text_urls": [ [] ] }

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{ "a_id": [ "gyv5jcv", "gyv5u1v", "gyv6lep" ], "text": [ "Both force extra air into the engine. A turbo uses exhaust gas to spin a turbine which in turn spins another turbine that sucks in air. More air means you can add more fuel and more fuel means MORE POWER. superchargers do the same thing but instead of using exhaust gas they have a pulley hooked up to the engine that spins a turbine/roots style corkscrew to pull in more air.", "Both are essentially a fan that forces air inside the engine, the more air you can fit in an engine the more power you can make The only difference between the two is how the fan is powered, in a turbocharger it’s powered by a turbine (which is where you get the turbo part) that runs off the exhaust, a supercharger is spun directly by the engine", "Both turbocharger and supercharger are trying to compress air to fit more in the cylinders so you can spray more gas in and get more power out of the same volume of engine. Supercharges are fed by a belt on the engine so they work at full capacity even at idle. Turbochargers are fed by the exhaust so they hurt a bit at idle and only really help at high RPMs A standard [turbocharger]( URL_0 ) is two axial flow turbines bolted together. For the hot side on the left, the hot exhaust is forced in around the edge of the fan which forces the fan to spin and the gas escapes through the middle on the axis(axial fan afterall) that the fan is spinning around. This fan is on the same shaft as one on the air intake that works the exact opposite by taking in air in the center and flinging it out to the sides. Now when the piston opens the intake valve the air rushes in because its at pressure instead of being pulled in by the piston alone. Superchargers come in a lot more varieties. Screw superchargers are basically two intertwined screws with a tiny gap between them. The threads on the screws grab the air and force it down between them into a higher pressure area. Superchargers are nice in that they give you boost at low revs which is good for performance, but also eat up a good chunk of horsepower which hurts fuel economy. Turbochargers extract wasted energy from the exhaust and use that instead of useful energy the pistons extracted so they can be used to improve the fuel economy of engines and let you use a much smaller engine for the same power/torque (see Ford EcoBoosts). Their main downside is not working across the power band but that has been resolved with a lot of modern designs that can move parts on the fly to change the turbo between a low resistance mode for efficient cruising and a high boost mode for high boost when needed" ], "score": [ 9, 6, 5 ], "text_urls": [ [], [], [ "https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Turbocharger.jpg/2560px-Turbocharger.jpg" ] ] }

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{ "a_id": [ "gyw8j6k", "gywkgg6", "gyx0zo9" ], "text": [ "I can't speak to PCI, but HDMI I know. So the data is serial but there are multiple signals. So for example in HDMI there are 3 wires for each of Red, Green, and Blue. Video is made of the 3 primary additive colors, RGB, so each is separated into its own signal. Each signal for Red, Green, Blue uses three pins/cabless for the balanced signal being sent. Balanced signal is a positive, negative, and ground. HDMI goes one way, so there is no \"receive\" going back to the source device. Balanced signals are used to decease interference. So thats 9 pins for the RGB (and audio since its embedded in the video). Three colors, times three signal cables for each. Then there is another set of 3 wires for timing signals. This is used to keep all three colors in sync. So that is 12 pins for the main video. The other 7 pins in HDMI are for various things. One is a low speed serial channel back to the source device for various things like EDID, and HDCP. A few pins for the ARC channel. There is a common ground for those channels. One pin is for 5v power, it can be used by adaptors to power a small chip for conversions, like a HDMI to VGA adaptor. One is for Hot Plug Detect. This is a very simple connection between the source and display so they can tell something was plugged in. In later versions 1.4+ a reserve pin and some others were given double duty to do ethernet over HDMI (100mb). That never really took off. The Wiki page has a pinout list: URL_0 So thats all the pins for HDMI. Why not just 2 wires, a Tx and a ground? History and the advancement of tech. When DVI or HDMI 1.0 came out, you couldn't send the full bandwidth of say 1080p video down one single cable. So it was split into multiple. For example, 1080p video needs 3Gbps of bandwidth. In 2000, you couldn't send 3Gbps down a single cable, you couldn't generate it and you couldn't read it (now maybe it was possible technically in 2000, I'm not sure, there is probably a price and ability to make it mass market consideration in there). Now, the advancement of tech can get 3Gbps down a single coax, like 3G-SDI. That is 1080p over a single wire. You can even do 12G-SGI and do 4k60 down a single RG-6 coax. But as the ability to send higher data rates goes up, so does the use. For example HDMI 2.1 is 48Gbps. Basically the 4 main channels (R,G,B, and clock) all running at 12Gbps (12 x 4 = 48), allowing for 4k120 (see note). USB-C and Thunderbolt are similar. They are serial data streams but you have multiple lanes of data. So each lane may do 10Gbps and then 4 lanes. Note: FYI, SDI and HDMI have different encoding schemes so while 1080p video needs 3Gbps on SDI, its more like 4.5Gbps with HDMI because of various overhead.", "I can't speak to HDMI, but PCIe I know. The simple answer is the analog of water passing in a pipe. Just as the water in a pipe goes 1 part of water (cross-section area) in series at a time if you watched closely. The simple difference of x16 vs. x1 is that you have a pipe with 16x the diameter vs. \"1x\" or \"normal\" diameter. Similar to how a fire hydrant is a very wide pipe, but a bathroom sink is a narrow pipe. Pipes allow water to flow in a straight line, with varying widths. Why is this useful? Some PCIe uses are for graphics cards that need that x16 diameter pipe to display your mind-blowing videos. Some use cases are just a slow wifi adapter that can use x2 or x4 because the pipe requirements don't need as much \"water\" or \"information\" all at once. Getting deeper, PCIe was invented for flexible use cases that were unforeseen at creation. They allowed a way for future uses to continue with the same interface for ease of computer design re-use (i.e. processor design re-use). Yes, it is a \"serial interface\" - but it's actually complex and using all those pins in parallel too. It's actually a configurable set of \"serial interfaces\" in \"parallel configuration\". If you need to know the details of a serial interface, it simply means that the data contains the clock embedded in the data signal itself. There is a \"PCIe Clock\" signal, but that isn't for data collection, just coordination at the low-level and proper reference alignment to ensure the 2x processors that are talking to each other know what is going on. The details are scary, so just reply if you must know. A real system has Processor < - > PCIe < - > Graphics Card (w/ Processor) < - > HDMI < - > Monitor Another example is Processor < - > PCIe < - > Wi-Fi Client (w/ Processor) < - - air - - > Wi-Fi Access Point (w/ Processor) < - > Cable/Fiber/ (puke) DSL", "PCIe is, at its core, made up of a transmit pair and a receive pair (*\"Pair\" is used to denote a \"Differential Pair\", a type of signalling method frequently used in high speed electronics that uses two wires for a single data line--using two wires and a 'differential' signalling method improves signal integrity and allows longer cables to be used*). These transmit and receive pairs can be thought of as two one way roads, one allows travel from place A to place B, and another from place B to place A. Now, when you have 1 transmit line and 1 receive line, this is called PCIe x1, where the number after the \"x\" indicates how many lanes the 'road' has. Think of it as two separate one-lane roads. A PCIe x1 link requires 4 pins: \"TX+, TX-, RX+, RX-\" (A positive and negative transmit pair, and a positive and negative receive pair). A one-lane road can only allow 1 car to drive down it at a time. We'll call this car \"Packet 1\". Packet 1 can travel from A to B pretty quickly, but before the next car (let's call it \"Packet 2\") can use the road, Packet 1 needs to reach its destination. And subsequent cars need to wait for Packet 2 to complete, etc etc. Now, if you ***add*** another lane to the road, now ***two*** cars can drive down it at the same time, allowing more people to travel from place A to place B at the same time. A two lane road would be PCIe x2. Now Packet 1 and Packet 2 can drive from place A to place B at the same time, and Packet 3 and Packet 4 will have to wait for the roads to become free. A PCIe x2 link uses 8 pins. You can keep adding lanes, resulting in PCIe x4 (16 pins), x8 (32 pins) and up to x16 (64 pins). When you have a 16-lane road, you can now have 16 cars driving side by side, meaning you have more room for more traffic, and you can get a larger number of cars moving from one place to another. So while PCIe is considered a type of serial communication at its most basic (PCIe x1), it can use multiple lanes in a parallel-***like*** method to dramatically increase data throughput. \\--------------------------------------- In the case of HDMI, the large number of pins is because there are actually 3 separate serial channels, along with a clock channel. Like PCIe, HDMI uses differential pairs for data transmission (a positive and a negative 'pair' of wires per signal); ***unlike*** PCIe, HDMI only ever goes one-way (meaning each channel only needs 2 wires/pins). Using the road analogy, HDMI is effectively a 4-lane, one-way road travelling from place A to place B. Lane 1 (red channel) only allows red cars, lane 2 (green channel) only allows green cars, lane 3 (blue channel) only allows blue cars, and lane 4 (clock channel) is reserved for police cars that keep all the other cars at the speed limit. As displayed images are made up of the colors red, green and blue, you need to combine the data of the red, green and blue channels while using the clock channel to synchronize the data received by the three serial color channels. TVs and Monitors have special circuits that can compose images based on the data received from these channels, and quite literally fills in the image in a similar way we read text on a page (it fills it in pixel by pixel across a line, then the next line, and the next, until the full image is ready and it then gets displayed). HDMI also has ***other*** pins that are not specifically used for sending image data from a PC to a monitor--these include a special 'power' pin, a CEC pin, EDID Clock, EDID Data, a Detect pin (to detect when something is connected), though these are specialized pins that are not necessarily required for sending serial image data from a device to a screen." ], "score": [ 14, 3, 3 ], "text_urls": [ [ "https://en.wikipedia.org/wiki/HDMI" ], [], [] ] }

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{ "a_id": [ "gyx65su", "gyx6oyo", "gyx60v0", "gyx6ubh" ], "text": [ "Ballast is a comparably cheap way of leveling ground that can support a lot of weight very cheaply. Rocks don't wash or blow away, they allow for thermal cycling, more or less self leveling, easy to repack when they do sag, easy to add new material to. Compared to say a concrete foundation, they won't crack, and doesn't require formwork during construction, and more importantly don't require extensive ground works before it can be placed.", "It is called ballast. The ballast is very stable and does not move whenever a train runs over it. So it will effectively transfer the weight of the train over a much larger area of the ground and preferably all the way into the bedrock. However the ballast is movable whenever there is constant forces. So if the ground moves the ballast will just adapt as the individual rocks will be able to fill any voids and get pushed away from any high spots. Similarly the rails gets longer and shorter depending on temperature and will move on top of the ballast. The ballast also helps with things like drainage and to keep the weeds away.", "Simplified: You need an element to take on the energy from the passing train and distribute it. It needs to be heavy not to just fly away. It needs to be flexible so it doesn't break, which is concrete or solid materials aren't a good idea (at least not with high speeds. You can use it when the train is going slow like at crossings or such).", "The term you’re looking for is [“Ballast”]( URL_0 ) which is a type of [“gravel”]( URL_1 ). To answer your question: the rails shift slightly, and expand/contract as the heat and cool throughout the day. Furthermore, the sit unburdened 99% of the time, but occasionally have to support weights of 1,000,000lbs or more. The layer of ballast keeps the track from moving without firmly securing it in place (which would snap the rail from the nontrivial expansion/contraction cycle). The first link I posted has a solid explanation (which I’m paraphrasing here)" ], "score": [ 47, 17, 6, 4 ], "text_urls": [ [], [], [], [ "https://www.google.com/amp/s/slate.com/human-interest/2013/09/why-are-there-crushed-stones-alongside-rail-tracks.amp", "https://en.m.wikipedia.org/wiki/Gravel" ] ] }

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{ "a_id": [ "gyyg1ur" ], "text": [ "Drywall is pretty unstable - it crumbles easily. So, if you put a (plastic) wall anchor in, it does two things: > -Gives the screw something stable to grip onto > -When the end of the screw exits the anchor, it pulls the anchor backwards, spreading into a T-shape that grips the back of the drywall" ], "score": [ 8 ], "text_urls": [ [] ] }

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{ "a_id": [ "gyzx1xi", "gz01a92" ], "text": [ "They actually are in many vehicles. Hemi is a trademark on an expired patent, and most vehicles use similar heads. Many vehicles also use double spark plugs.", "Most things that are mandatory on a vehicle relate to safety, except a few mandatory emissions components like a catalytic converter. But for the most part, environmental agencies just dictate a certain standard like X fuel efficiency or under Y emissions by Year XXXX. How manufacturers get there specifically is left up to them. Hemi heads have given way to active heads which lean on the idea of circular shapes but aren't pure just circles as they're designed to swirl and tumble the charge to create even better efficiency, so pure hemi heads are *not* the best design. These active heads even allow higher compression ratios on lower octane. As for dual Spark Plugs, you can also get single spark plugs that do multiple sparks. But GDI technology is supplanting the need for that. Since you can now arbitrarily decide when fuel enters instead of *having* to be brought in with the air and then compressed with it, along with modern spark timing drawing on decades of design and study on the subject, you can choose to have a high-performance combustion or a nice slow roiling flame front, just enough to keep the motor moving. On top of this, turbo is becoming more and more the norm. All this tech adds up, the Chevy 1.3T EcoTec can produce over 150 HP with an 80c.i. motor, that's nearly 2 horses per cubic inch, that's actually pretty dang efficient." ], "score": [ 3, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gz1n8np", "gz1y5zl" ], "text": [ "In my experience, it's usually the voltage that's trying to move the speaker cone. Or rather, it's the voltage that gets sent to the amplifier, and the amplifier then outputs a different voltage (depending on gain) to move the speaker cone.", "There are different standards based on what you are recording from. CD players, tape players, TV players, mixers, etc output line level, where maximum volume is around 0.3v - 1.4v. Microphones output tiny voltages, somewhere around 0.001 volt. Instruments (electric guitar) put out around 100–300 millivolts. So whatever you are trying to record, you need to be sure to connect it to the correct type of amplifier (if required) before connecting it to your analog to digital converter. Then you will still need to adjust levels in analog until you get levels you are happy with in digital. There is no defined conversion values from volume in the real world, to voltage, to digital value. You use whatever values work for your particular situation. This means if you record two different things with different equipment they won't have their correct relative volumes once recorded. So if you are making a movie and you've recorded dialog and sound effects separately, you are going to need to adjust the levels in your video editor until they sound correct." ], "score": [ 5, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gz62dk4" ], "text": [ "DRS is the drag reduction system; it's basically a flap built into the rear wing of the cars that opens up on long straights, dramatically reducing the aerodynamic drag on the cars and allowing them to go faster than they normally would. The system was explicitly introduced to make it easier to pass, which is notoriously difficult in Formula 1, all to make the races more exciting, and make it a bit more difficult to maintain the lead. It's regulated with a special timing trap at the beginning of the part(s) of the track where DRS is allowed; if you are within 1 second of the car in front of you when you go through the trap, you're allowed to trigger the DRS on your car. It's also disabled by the FIA in dangerous situations, particularly the first few laps of the race, partially for safety reasons, and partially to reward the results of qualifying." ], "score": [ 5 ], "text_urls": [ [] ] }

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{ "a_id": [ "gz78m5l", "gz78hoi" ], "text": [ "That probably won’t help much. The cab forms something called a Farraday cage (at least that’s what I think it’s called), meaning that all charges stay on the outside of a hollow conductor. For that same reason you’re also quite safe from a thunderstorm inside your car. Unfortunately you’re only safe inside of a farraday cage meaning that if you hit a power line anybody touching your heavy machinary is likely going to be electrocuted.", "Push enough juice through anything and insulation won't matter much. Power lines contain enough juice. Death can be caused by superheated metal just as easily as it can be caused by electrocution. As is a fall from power line heights. The desire to have people not whack powerlines is as much in the interest of not destroying power grid infrastructure as it is for saving lives." ], "score": [ 7, 5 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gza8t7h", "gza8ajp", "gzaa1re" ], "text": [ "Diesel engine and gearbox that would match the high speed performance of a petrol engine and gearbox would be much heavier. Diesel engines tend to perform better at lower revs but cannot spin as fast. Petrol engines tend to produce more power at high revs. This is why diesels are used for high load/low speeds and petrol more for high speeds. There is nothing that technologically prevents diesels from being used in sports cars. It is just that lot more money has been spent optimizing petrol cars for racing.", "Aren’t most, if not all, of the Le Mans Prototype class 1 sportscars diesels?", "Diesel engines are heavier, and because of their smaller powerbands they require more extensive (and more massive) geartrains. Thus, the increased efficiency and torque in diesel engines generally doesn't amount to increased performance because of all of that additional weight, and as a result the only motorsport where diesel engines show up is in Le Mans-style racing (where weight isn't as big of a deal in comparison to torque). However, this is starting to change, particularly given that motorsport seems to be moving towards hybrid powertrains (where the diesel engine powerband issue goes away). Further, a lot of the current research on diesel engines is focused on reducing weight, while spark-ignited engines don't really have anywhere to go in terms of power and efficiency." ], "score": [ 5, 3, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gzcqz7d", "gzd11d7", "gzcrief", "gzcqrsw", "gzctgrs" ], "text": [ "In certain parts of the world, there is a layer of water saturating the ground under the surface. This is called the water table. Pretend the water table is 9 meters below the surface. If you then dig a hole 10 meters deep, it will penetrate the water table. Water will flow into the hole, filling it to a depth of 1 meter. Water then can be removed from the hole, which is now called a well.", "Follow up question, how do you know where to dig a well? Are there signs of water being present 9 meter underground?", "Most areas of land on earth have water in the soil. This water slowly flows towards a river or other body of water. This flowing water covers vast areas known as \"aquifers\". If you drill down to the depth of your local aquifer (that depth is known as the water table) the hole you dug will begin filling with water from that aquifer. A well is that hole. Modern wells use a solid well casing with a bottom made of gravel. The water will push up through the gravel in the bottom. and filter out any large contaminated like dirt and then it will be pumped to your house. Older style wells typically jusy line the wall with stones and no cement so the Ayer would flow in from the walls as well. However they would dig it deep enough that the dirt would settle out below the bucket. As cement was developed wells were reinforced on the sides and then the bottom was left as gravel much like a modern well.", "Groundwater. Picture like mini rivers under the land surface. When you dig deep enough, water will either come through and/or seep into the hole. r/hydrology r/hydrogeology", "Speaking of the water table filling the void of the well with water, would this not happen to coffins too?" ], "score": [ 49, 10, 8, 5, 3 ], "text_urls": [ [], [], [], [], [] ] }

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{ "a_id": [ "gzdv3yx", "gzduq0k", "gzduwnr" ], "text": [ "The halting problem asks \"is there a way we can determine for certain a given program will finish or run forever?\" Let's assume that there exists some program P that can solve the halting problem. In other words, P takes in some other program as its input and returns if it halts or not. Lets then make a program Q that takes in a program as its input and does the opposite of what P does, if P says the input will halt then we'll run forever and vice versa. We can write this in pseudocode as def Q(I): if P(I): loop else: return What happens if you pass Q in as the input to itself? If P says \"Q will halt\", then Q will run forever. If P says \"Q will run forever\", then Q halts. This leads to a contradiction as we defined P as being able to solve the halting problem for any given program, but yet it fails here. As such, the halting problem is impossible to solve. There will always exist some program that is undecidable.", "The halting problem is an example of a problem that can not be solved and that can be proven to not be solvable. This has some profound implication for mathematics and computer science, as it can be used to prove that some problems aren't [decidable]( URL_1 ). ************ It goes like this: imagine you have a turing machine (which is basically an abstract computer), that takes as input an other turing machine, a program for it and some input for that program, and outputs wheter the machine run the program to the end and halt or if it get stuck computing forever. So it basically tells us if the input machine ever halts. Let's call this machine *h*. Using *h* we can create a machine *h+* that takes the same inputs as *h*, and loops forever if *h* says it halts and halts if *h* says it doesn't. If we feed *h+* into itself then *h* has to decide if *h+* will halt. But by construction, if *h* decides that *h+* should halt, then *h+* never halts, and if *h* decides that *h+* won't halt, it does. So this machine that can know if a turing machine halt given a set of inputs can never exist. ********* [here is a video with nice animations about turing machines, decidability and the halting problem]( URL_0 ).", "The halting problem is to determine whether there is such an algorithm that could determine for every possible algorithm whether it will keep running forever or stop (halt) at some point. It turns out there isn’t such an algorithm. The proof is to assume that there is and come to a paradox. The paradox is as follows. If the algorithm halts(f) determines halting or non-halting for any algorithm f, then we can build a recursive algorithm g like this: if halts(g) then run forever. So if the algorithm “halts” says that g halts, then g will keep running forever. If it says that g keeps running forever then g halts. The paradox proves that our assumption was wrong and there is no such algorithm “halts”." ], "score": [ 20, 6, 5 ], "text_urls": [ [], [ "https://youtu.be/HeQX2HjkcNo?t=1333", "https://en.wikipedia.org/wiki/Decidability_\\(logic\\)" ], [] ] }

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{ "a_id": [ "gzf3x1e" ], "text": [ "All that stone material acts as a great insulator. It doesn't transfer heat well, so homes and buildings made out of stone like that don't heat up much in the summer and don't cool down much in the winter. It's one of the big benefits to making buildings out of concrete, clay, or stone. Really saves on heating and cooling costs. You'll see these kinds of buildings a lot in hotter environments, especially around the equator. The big benefits to wood are that it's cheap, lightweight, easy to work with, and readily available just about everywhere on the planet." ], "score": [ 9 ], "text_urls": [ [] ] }

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{ "a_id": [ "gzf4t27" ], "text": [ "The physical setup should be self-explanatory. If one gear has 24 teeth and another gear has 12 teeth (of the same size), the turning the 24-gear once will turn the 12-gear twice, just because of the size difference. Now, think about the energy you use to turn the gears, or work. The work you put in, minus the losses to friction, will be equal to the work that comes out; this is the conservation of energy. Work is also equal to the integral of force over distance; more simplified, work is equal to force multiplied by the distance this force is applied. So if you are putting work into turning the 24-gear and the 12-gear is turning twice as fast, the work has to balance out. In order for the work to balance out, the force exerted by the 12-gear must be half of the force you're exerting on the 24-gear. F/2 x 2D = F x D. And the same is true the other way. Each turn of the 12-gear moves the 24-gear half as far, so it must exert a force twice as large in order for the work to balance. 2F x D/2 = F x D. Torque is just rotational force. So the gear that spins faster must produce more torque, and the gear that spins slower must product more torque." ], "score": [ 9 ], "text_urls": [ [] ] }

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