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{ "a_id": [ "glbkmtk", "glcbw8o" ], "text": [ "If the drum was rigidly mounted, your washing machine would walk across the floor and start banging into walls. Washing machines actually have a dynamic balancer (usually a [liquid]( URL_1 )), so that an uneven load will be automatically counterbalanced. Mounting the drum loosely allows a slight imbalance to occur, which flings the counterbalance mass to approximately the opposite side of the imbalance. It's not perfect (and can't be without active computer control, which would be expensive) but it's pretty good. It's a very similar principle to [dynamic tire balancing beads]( URL_0 ). If your load is still really unbalanced, your imbalance has exceeded the mass of the counterbalance. Reduce the amount of weight in the drum (1 blanket at a time) and that should help.", "Maybe the washer's shock absorbers have failed. I had to replace the shocks in mine when it rocked'n'walked itself forward to block the washroom door. (first I had to get back into the washroom)" ], "score": [ 7, 3 ], "text_urls": [ [ "https://tundraheadquarters.com/bead-balancing-tires/", "https://www.researchgate.net/publication/225194935_A_dynamic_model_and_numerical_study_on_the_liquid_balancer_used_in_an_automatic_washing_machine" ], [] ] }

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{ "a_id": [ "glcmshi", "glcmt5n", "glcnugl", "gld7nnd", "glcndua", "gld6q1y", "gldiwzg", "glcn48u", "glcm2k7", "gld8xr5" ], "text": [ "Well it can pretty much be summed up by: they solve problems and make sure stuff is done according to regulations and standards. In R & D engineers will look for innovative solutions to existing problems or look for optimisation in existing systems. In quality assessment, they make sure that the products “performance” is in agreement with regulations and what is advertised. In a factory the engineer is more or less responsible for making sure that everything runs smoothly by addressing small issues before they become dangerously at risk of hindering the production facility. In design, they... well, design pieces / tools / machines/ constructs according to a list of expected properties and with respect to the regulations. There is way too much different occupation an engineer can have to list them all but as I said, it almost always involves solving a problem.", "I work as an electrical engineer. There are different types of electrical engineers. I'm an ASIC engineer. We make integrated circuits. Typically, we design hardware using some kind of hardware coding language, like Verilog or VHDL. In order to make sure our hardware code works properly, we need to test it. These tests are basically simulations that make sure the hardware code does what it's suppose to do. When the hardware code passes all the tests, we then need to convert the code to actual hardware. This is done using two processes called \"synthesis\" and \"place and route\". Synthesis generates all the lego pieces that make up the hardware. Place and route takes those lego pieces and figures out where to put them on the actual die. Once the design has been implemented, we send the design to a fabrication facility and they print out the design in silicon. At this point, the physical hardware exists in our hands. But we're not done yet. We need to do more tests to make sure the hardware works in real life. Just because the hardware worked in a simulation doesn't mean it's going to work in real life.", "engineers are problem solvers with math, science and design foundations. they have unique specialties depending on the job/degree.", "You can classify \"engineers\" into two categories: Formal Engineers (capital E) are recognized as having completed a 4 year Bachelor of Science program at a university. Besides deep coursework in their field of study they'll also be exposed to intro courses in other fields. For example, a mechanical engineer will also have intro courses to electrical engineering, computer science, etc. Formal engineers will often gain additional accreditation particular to their field a few years after graduating. Informal engineers (lowercase e) might have taken formal coursework, or they can gain their education on the job, or be self-taught, or do vo-tech style \"bootcamps\". Informal engineers are often \"engineers\" in title only, and you'll see this title applied liberally in software, sound, process design. In my experience I've had great people for both camps, and absolutely lousy people from both. So the title doesn't really mean much unless you're looking for a very specific kind of job. In terms of \"what they do\": Pretty much anyone can figure out how to build a bridge across a body of water in a brute-force way. What an engineer does is figure out how to build that bridge with the minimal amount of material, labor, and disruption while maintaining a high level of safety and maintainability. This basic idea applies all sectors of engineering. Anyone can learn how to program something in an afternoon and theoretically, given enough time, be able to program anything. But if that's all they learn about programming, their final product will be extremely slow, impossible to maintain, won't scale, and might take several lifetimes to complete. A software engineer might be able to produce the same product in a few weeks and have something superior. In terms of actual work: It really depends on the specific job. But generally you're given a unique problem and asked to solve it, either solo or with a team size ranging from another guy to thousands of people. I might hire one engineer to solve a structural problem with my house, or I might hire thousands (with many many layers of management) to design my next gen aircraft career.", "My bf is a mechanical design engineer. His job is to design new products, or change the design of existing ones, to solve a problem or improve how things are done.", "High level: In one of my first classes in eng school (EE) a professor asked us the students this very same question. His final answer was \"1) optimize processes, and 2) lower costs\". This has stuck with me since.", "Structural Engineer: Design buildings so they stand up and remain inert as possible for their lifetime. You end up specializing in building types a bit - eg: flat slab construction for office and residential high rise, “bridges”, historic preservation, low rise institutional (eg schools and hospitals). I like it. Good variety of projects, very tangible end product, get to see the world being built up close, the profession allows travel - it’s easier to move both nationally and internationally than a lot of professions, IME. Pay could be better... Education requires a strong foundation in math and physics in high school, then an engineering degree (unless you’re in California) that goes into a lot more math, along with application of the math to structural solutions and related fields (surveying, geographic information systems, systems optimization, introductory coding), along with introductory courses to various engineering materials (steel, concrete, wood) along with some low-temperature fluid mechanics and soil mechanics. Most of this is geared around what you’ll be doing if you go into research. If you go into the construction industry most of it becomes “background” that you need to have an understanding of but will literally never use. You could go an entire successful career in design never having to use anything other than the plus/minus and multiply/divide buttons on your calculator. This is true of many professional degrees. Work involves working with an architect to find a compromise between their goal of a column-free, wall-free, slab-free building and one that will stand up, then working out with the HVAC/Elec/Plumbing engineer to work out how badly they can perforate my structure (from their perspective they’re working out how to make a habitable building with all my beams in the way stopping shit from being able to flow downhill. Lots of computational design using structural modeling software, understanding structural systems and lots of understanding of local and national design codes for respective building types and materials, lots of coordination with other professionals on the team. The product of the design process is a series of structural drawings showing exactly what needs to be built - every beam size and location, every column, every slab, every slab opening, and details for every non-typical condition. There’s a lot of technical drawing involved. Once the project is under construction the engineering team has to review a large set of shop drawings produced by the various construction contractor practices to make sure they’re understanding the design drawings correctly, and then answer questions and solve issues that come up on site. Lots of communication with the Project Management team from the general contractor who range from “have degrees on related field” to “left school at 14 and spent 30 years working their way up”. Engineers get a lot of shit about being introverts and a bit weird socially (not entirely untrue... there are plenty of oddballs) but in any construction related engineering field you need pretty good communication skills as you’re going to be part of a large team spanning multiple companies where clear communication of what everyone is doing is essential, and this gets more and more true the further you go in your career. As you get more and more experienced you also end up doing less and less actual engineering. Eg: Starting out your day will look like: 4 hours column design for Project A 4 hours shop drawing review for project B 30 mins meeting with project manager Then will slowly transition to 1 hour consultant meeting Project A 1 hour coordination call with architect Project B 1 hour construction admin meeting Project C 1 hours various meetings with junior engineers on Projects A, B and C 3 hour design Project B and E 1 hour internal project management coordination meeting 1 hour billing, project financials, project admin This will then slowly move to: 30 minutes business development (BD) call with Client A 30 minutes BD client B 30 minutes BD client C 1 hour BD client D 1 hour project financials review (all office projects) 1 hour firmwide leadership meeting 30 minutes office quality control meeting 30 minutes structures practice group leader meeting 30 minutes project review Project E 1 hour fee proposals Projects F, G", "They design how to build things and ways to fix things. Then technicians go physically do the the work. Trust engineers to overcomplicate the explanation!", "Ooh one I'm [qualified to answer!]( URL_0 ) Answer is it depends. There are different fields of engineering (mine is aerospace) and different roles within those fields. Specifically I work in what could basically be described as data crunching and analytics to improve reliability of products currently in service. There are other engineers who do the actual designing. Others who do quality control. Others who do research. I can't get too specific about what I do daily for legal reasons, but I spend time in various software packages and move numbers so they can be crunched or results can be presented to those who make decisions. Generally you start by picking a field aero vs mechanical vs electrical etc. Then within those fields you kinda see what interests you and what job openings are a thing. By the time I graduated I knew what types of positions I would want to gravitate more towards. Hope that helps. Feel free to ask any other questions.", "I’m a civil engineer, more specifically I do utilities (water/fire, sewer, storm drain). I basically do the same thing the Romans did thousands of years ago. Someone above answered it well; practical application of science to solve problems. Engineers design things to work, more specifically to just barely work (anyone can design a storm drain pipe big enough, but you have to know what you’re doing to make it barely big enough). In the glass half full/half empty question, engineer’s answer is, “the glass is too big.”" ], "score": [ 115, 24, 23, 11, 8, 7, 6, 4, 4, 3 ], "text_urls": [ [], [], [], [], [], [], [], [], [ "https://i.imgur.com/WlWdTZ5.jpg" ], [] ] }

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{ "a_id": [ "glclbjb", "glcm1f3", "glckhdc", "glcoj6o" ], "text": [ "This sensor is known as a float, and the name is pretty straightforward. Sucker floats. It is not a particularly precise instrument, but it gets the job done. While fuel may slosh around some, this is significantly reduced by the presence of baffles in the tank. Partial walls that seriously hinder the fast and rhythmic movement of the liquid while taking up very little space. Additionally, a few other systems may be used to get a more accurate readout. This part is speculation, as I've never personally disassembled a gas tank/float, but: Even as it moves around, the average liquid level does not change. If you can slow the movement of the float by some mechanical means, you can prevent it from wandering too much as the liquid sloshes. Again, the device doesn't need to be precise; it just needs to give you a rough idea (within a gallon or two) of the liquid level. This solution would not work if the sensor needed to detect rapid changes in liquid level, but hopefully your gas tank isn't draining all that much in a fraction of a second. Another improvement is to place the float at the center of the tank. During longer periods of consistent acceleration, including turns, the surface of the fuel becomes angles. For instance, during a left turn, the right side of the fuel raises while the left side lowers. The solution may be obvious, when the problem is presented like this. By positioning the float at the center of the tank, it does not experience any significant disruptions from the fuel 'tilting' in the tank.", "A typical modern car has a fuel level sending unit using a mechanical \"float\" at the end of a pivoting rod. It literally floats on the fuel level, and converts the angle of the pivoting rod [into a voltage reading]( URL_0 ). You're right when you say fuel sloshes around. So a modern car will use a microcontroller-based \"fuel gauge damper\" circuit to take suitable averages of the incoming \"noisy\" voltages, and convert that into a stable signal for controlling the gauge.", "It actually doesn't most of the time. In my car I have about a gallon and a half (based on milage) after my tank says empty. Solid life protip. When you get a new car fill up a gas can and see exactly how many miles you get until it actually runs out of gas. Not sure about more modern cars but in older cars it was just a floating sensor that detected how full the tank was.", "Just like the temperature gauge in a car, it doesn't react to short-term changes. The input from the sensor (it's usually just a swimmer) is filtered before you see the results in the gauge. Fun fact: Your engine's temperature goes up and down all the time, sometimes above 110°C, and the gauge will still not show it unless it remains there for a longer period. Manufacturers chose to do this so people wouldn't phone up the service all the time." ], "score": [ 11, 6, 5, 3 ], "text_urls": [ [], [ "https://en.wikipedia.org/wiki/Potentiometer" ], [], [] ] }

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{ "a_id": [ "gldgqi0" ], "text": [ "It's your overall architecture for collecting data, storing it, training models on it, and using those models for real-world tasks. So when you're just learning ML in school/tutorials you usually just download your data file and run your Tensorflow/Keras and that's it. But in real world settings data is coming in all day and you need to write code to handle this (and more): * What source does your data come from? * Where do you store it? * What format? * Is any aggregation/processing needed to make this data useful for ML? * How often do you train models? * How do you test models to make sure they're not broken and far less accurate than what's already running?" ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gldk55i" ], "text": [ "Well \"equal\" is probably not happening. \"Pretty good\" is a more reasonable goal. When they set up all the speakers, they do testing of the resulting sound to find and correct for harmonic properties of the venue. Even as people are listening to the warm-up act, they are fine tuning the equalization to factor in the sound absorbing properties of the crowd." ], "score": [ 4 ], "text_urls": [ [] ] }

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{ "a_id": [ "gldnz7d" ], "text": [ "Petrol and gasoline are the same things just referred to as either or in different parts of the world. A standard bang engine squishes air and fuel to create bang when ignited by a spark. Bang resistance is the ability for the mixture to not bang until the appropriate time while being squished. If the mixture is banged before the appropriate time it can cause issues. Much like drumming off beat. If you hit your drum at the wrong time it will sound bad. Diesel is a different substance that has a much higher bang resistance number since they are used in high bang diesel engines. Diesel engines can produce low power but high pulling force. High pulling force is necessary for towing big things like boats or trailers. Most petrol / gasoline stations have three types of bang residence metrics, But can also vary depending on your area. In my area the following are the most common: 87, 90, and 93. Some race cars use 100 bang resistance fuel because high bang engines make the car go faster Some brands of fuel will add other things into the fuel to help the fuel create more efficient power or help clean your engine too." ], "score": [ 13 ], "text_urls": [ [] ] }

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{ "a_id": [ "glerggr", "glfcbzm" ], "text": [ "For ELI5, it's the cement put between bricks and rocks when building walls and floors. While the bricks or rocks will be complete and dry, mortar is applied while wet, and dries on place. It's essentially cement glue, and holds the bricks in place. It's a little different than concrete, still made with cement and lime, mixed with sand and small stones, appropriate for the use case and aesthetics desired. The ratio of ingredients is what separates ~~cement~~ concrete from mortar, with ~~cement~~ concrete having a lower water-to-cement ratio, and often larger particulates like gravel with the sand. Edit: correction that concrete has lower water-to-cement, because cement there makes no sense...", "The cement isn t some sludge that dries up, then solidify like mud would. Adding water triggers a chemical reaction that changes the composition of the cement and make it hard like a brick." ], "score": [ 14, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "glfkd8j" ], "text": [ "As a building engineer who oversees buildings as they are built and then maintains them when they are complete its rather simple. Most commercial buildings are made with materials that are not drastically affected by the weather. Steel beams, concrete etc.. they rough in the building with these materials until they are ready to seal it up. Windows and roofing etc... then afterwards they finish the interior off floor by floor. If you look at things like the beams after the building is finished you’ll see they are rusty but no where close to rusting through." ], "score": [ 4 ], "text_urls": [ [] ] }

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{ "a_id": [ "glgbe2p", "glgbq4w", "glgc130", "glgbxny", "glgg83t" ], "text": [ "While I'm not sure which particular part of the tower you refer to, I'll give a brief rundown. However, not all electrical towers *are* designed like that. The wire-frame shape of the tower allows it to use far less material than a solid structure while still retaining the strength and rigidity necessary to stand. The frame is composed of struts forming triangular structures, as triangular structures do not experience bending in their bars - they instead experience compression and tension. It is much easier to break something by bending than by pulling straight on it, and so this again saves on material while keeping the tower sturdy. The widened base allows the tower to resist significant sideways forces without tipping; the force that these wires apply to their towers is actually quite large, simply because of how big and long and taught they are. The arms of the tower serve to keep the conductive frame far enough away from the extremely high-voltage power lines that there is no risk of electrical flow between them. The weird corrugated sections connecting the wires to the arms are insulators. They minimize the electrical leakage into the tower, while keeping tension on the wires.", "The transmission line or the steel tower is designed that way to support itself at that high of an altitude. Think of it almost like the Eiffel Tower in Paris. Then all the different \"ropes\" you see are the different phases of voltage (A, B, C, & a ground wire). The different phases have to be a certain distance apart from each other so that you don't have phase to phase faults. This is a quick and concise answer (but not as detailed as you might want 😅).", "There are 3 sets of conductors on each side because in most countries, industrial power is 3 phases. Electricity is boosted to extremely high voltage when travelling across long distances because it minimizes power loss through heat. The problem is, high voltages allow power to jump across gaps in the air on to the tower and eventually through ground. That's why you see those stacks of disks that attach the line through the ground. They are ceramic disks that are non-conductive that maintain the wire's distance away from the tower.", "Well starting at the bottom the base has to be wider than the top to avoid it tipping over as easily. The criss-cross structure is known as a truss structure and is a design that allows a lot of smaller members to comprise a larger structure by setting them up to carry tension and compression loads that oppose the other members to keep the structure rigid. The top of the transmission tower has those huge yard arms to hold the wires. They are spread out so far to prevent arcing between the wires and the big coil spring looking things are insulators to prevent the electricity from transferring into the structure of the tower and shocking people. Again they’re so long to prevent arcing", "It doesn't \"need\" to have that shape. But it does need to: * hold up very heavy cables, thousands of pounds * hold them pretty far apart from each other * hold them very high in the air * be strong enough to do all this while also resisting wind, snow, ice loads * be cheap enough that we can build one every few hundred feet for 1000s of miles Seems like a tall skeletonized/geometric shaped tower with some arms at the top and a lot of internal triangles for strength, all made of cheap metal is a pretty good solution to all those criteria. So many of them look pretty similar to that, although [many different shaped towers within that general theme]( URL_0 ) are in use." ], "score": [ 48, 3, 3, 3, 3 ], "text_urls": [ [], [], [], [], [ "https://i.pinimg.com/originals/d5/f5/50/d5f550c2da3b1a6600f7ec4b0b8e82bb.jpg" ] ] }

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{ "a_id": [ "gliwtup", "gljasm6", "gljcyyo" ], "text": [ "Whistles work by having a slot for air to move through that then hits something that splits the air into two different directions. The part that the 'air splitter' is connected to is made of a material, like wood, that will resonate at the frequencies that the disturbed air will vibrate at, which in turn makes the sound of a whistle. [ URL_0 ]( URL_1 )", "What are you trying to figure out? URL_0 Looks extremely straightforward to make a simple whistle (not tuned to any particular note). Note that the blowing end does need to be mostly closed off. There's no black magic formula here: as you see in the video, the guy doesn't measure anything. All that matters is that the air is directed towards the splitter and that the tube is long enough that the whistle be audible (unless you have a dog then even a very short tube will produce an observable outcome).", "How whistles works: there is a blade that redirect a stream of air inside, then outside, then inside, then outside, etc... How? The inside is a closed cavity, when the air goes inside, it increase the pressure, which quickly push the stream of air on the other side of the blade and make it go outside. When the air goes outside, it catch some of the air from the cavity with it, thus decreasing the pressure, and eventually redirecting the air towards the inside of the blade. The size of the cavity will change the tone. The blade need to be sharp and right in the middle of the incoming air jet. The only exit/entry from the cavity must be through the jet of air so as to deviate it." ], "score": [ 10, 5, 4 ], "text_urls": [ [ "http://www.physics.mcgill.ca/\\~guymoore/ph224/notes/lecture23.pdf", "http://www.physics.mcgill.ca/~guymoore/ph224/notes/lecture23.pdf" ], [ "https://www.google.com/search?client=firefox-b-d&q=make+a+wooden+whistle#kpvalbx=_5z8XYOu1CJSo5NoPrKSCyA414" ], [] ] }

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{ "a_id": [ "gljqivh", "gljs1z8" ], "text": [ "So it doesn't overcharge. Kinda like you can fill a bucket with water fast at first but need to slow down as you reach the top so you don't overfill.", "Think about filling up a bucket, but if you spill too much water the bucket explodes violently. Sure, you can go fast at first but then at the top you better slow down." ], "score": [ 4, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "glk7puz", "glk7h3n", "glkan59", "glkcu58" ], "text": [ "Arches are the best at bearing loads, but are not the more practical. Advances in materials and design make it so we don’t need to use _the best_ system. If a Ferrari is the best for going fast (for argument sake) why would you ever buy a luxury car? Shouldn’t pizza delivery deliver in a Ferrari to save time?", "Because modern building techniques dont rely on tension destribuition in localised spots as instead tension forces are distributed throught the steel beams on the inside of the buildings. Also has to do with regionalism, places where there was such architecture tend to show modern examples of old techniques, in example in Italy and Portugal romanic arches are more comon in the south and gothic arches in the north, in Ohio or Montreal neither are common", "Aches have a huge advantage if you build in a material that has high compression strength but low tensile strength. That means strong if you compress them but week if you try to pull them apart. An example is concrete, bricks, stones you put together with or without mortar The advantage is a lot lower if you have material that can have high compressive and tensile strength. Examples are steel, reinforced concrete. You have a lot of arches in old stone building because that was the only way you could build it and support the load. Today you can do the same with horizontal steel or reinforced concrete beams. There is a relatively well know the quote > Any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands. The general meaning is that building something strong is not hard the problem is if you what to build is at a reasonable cost. For a building, there is also the amount of usable space, windows sizer etc. There is a lot of prefabrication today where you move the part to the building site and assemble there both steel and reinforced concrete. The flat part is simple to make and simpler to transport It is not hard to build stuff that survives earthquakes, hurricanes, and high winds. It is hard to do that at a reasonable cost and having a large internal volume. So arches are a lot less needed today than in the past because we can build strong enough without it at a lower cost. If you see a short arch it is likely for the visual, not the strength. But they are still used when it is the best option like if you build a [concrete bridge with a ]( URL_0 )[445-meter]( URL_0 )[ span]( URL_0 )", "Arches can be good if you don’t care about the depth required for a structure to work. Look at all the buildings you see where there are arches as the primary structural system - the floor to floor heights are **enormous**. This is because you need a huge depth of structure to work, especially around the perimeter. Once we developed structural durable materials capable of taking tension (ie steel) we moved to structural systems that are much more efficient, and require a much shallower structure. Instead of a 20 foot tall arch you can have a two foot steel beam system. This enables high rise construction. Masonry arches, the type of arch you see in buildings, are also very very heavy compared to structural systems we use today - so for multiple floors require enormous foundation systems. They’re also not great in earthquakes - the enormous mass means they pick up enormous earthquake forces, but aren’t very ductile so have bad failure modes when trying to dissipate those forces. The cases where you do still see them are things like bridges where the height of the structure isn’t often a critical concern, and in these cases can be efficient structures." ], "score": [ 25, 17, 15, 4 ], "text_urls": [ [], [], [ "https://en.wikipedia.org/wiki/List_of_longest_arch_bridge_spans#/media/File:Qinglong_Railway_Bridge.jpg" ], [] ] }

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{ "a_id": [ "gllgwxs", "gllf9ta", "gllltl2" ], "text": [ "4WD and AWD have really got mucked up by marketing teams, but if we take the more traditional routes with AWD being always on with a center differential and 4WD being engagable with a Transfer Case in the middle then you can start to see problems For an AWD system with a center differential there is also a front and a rear differential so the wheels can spin at different speeds if they need to incase one gets stuck or is just on the inside of a sharp corner. The Transfer Case does not permit differences in speed between the front axle and rear axle, the average speed of the rear wheels needs to match the average speed of the front wheels, but when you go around a corner this isn't usually the case. If you only use your 4WD in slippery conditions then this isn't an issue because at least one of the wheels will slip on the mud/snow/ice, but if you run 4WD on dry grippy roads then every time you go around a corner there is a lot of twisting force being applied in the transfer case as the front and rear wheels attempt to travel at different speeds, in sharp corners you can hear the wheels skip as they lock up and have to break free from the road.", "when you turn, your inside tire needs to spin at a different speed than your outside tire. 4WD doesn't allow this on pavement because 4WD locks your differential. you scrub your tires and put stress on your drivetrain.", "Traditional user-selectable 4WD systems found in trucks (typically) are designed to be engaged by the user - either via transfer case or by locking the center differential. When engaged, they require the front and rear axles to turn at the same rate. This is great off-road but taking turns on dry pavement results in drivetrain binding/tire skipping/scraping as the wheels try to turn at different speeds while the drivetrain fights it. Naturally this is a lot of stress that doesn't need to happen and can result in anything between tire wear to something on the vehicle giving up. Same reason you should not drive around town with a differential locked. Great off-road when traction between the tires can vary, but horrible when they all have grip and you have to turn. This isn't necessarily applicable to ALL 4WD systems since some may be designed for permanent use and others may have an automatic mode." ], "score": [ 27, 6, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "glmdua8", "glmf4kh" ], "text": [ "As I recall those are not to ignite the engines. They are there to burn off any unburnt fuel that comes out of the engine before the engine ignites itself, avoiding a situation where a large amount of unburnt fuel builds up around the engines before ignition. Which may lead to a fireball or explosion. Edit: typos mostly.", "The Space Shuttle main engines ran on hydrogen and oxygen, the sparkers aren't there to start up the main engines, they're supposed to burn off any hydrogen that gets pumped out in the second while the engine pumps spin up but aren't ignited The Delta IV also runs off hydrogen/oxygen fuel but doesn't have these sparkers. If you watch a Delta IV launch you'll see a big orange/red flame whip up the side as all the excess hydrogen is ignited. This is a lot sketchier on a reusable space shuttle with people on board" ], "score": [ 15, 4 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "glmoq3t", "glmqz2x" ], "text": [ "actually, Most cars use a Inline engine, In a traditional engine, you have pistons that go up and down and that linear power is converted to cyclical power using a crank shaft, which is basically like bicycle paddle, so when one piston pushes down, the crankshaft pushes another piston up and so on. Wenkel thought it would be more efficient to make a engine where the pistons spin on their own axis removing the need for a crank shaft, so he designed a triangular piston which is actually 3 pistons in 1, And since theres no need for a crank shaft to convert the power from linear (up down) to cyclical the power delivery to the transmision is more efficient. So you have engines which are 2-3 cylinder (actually called a rotor in wankel engines) which have a displacement of 1.2 or 1.4L which produce as much horse power as a linear engine 2-3 times its size. so you have a lighter, more powerful engine in a smaller displacement, but at a cost. since the cylinders chambers arent fully sealed, you need special seals on the corners of the triangle or you´ re going to get oil and gasoline leaking in to the exhaust and poor compression/power loss. and it requires oil to be mixed in the the gasoline, also fuel consumption is elaved compared to an equivalent linear engine. and reliability is much lower. basically every time someone has tried to bring back the rotary engine, 80k miles is enough to teach you that rotary engines might be great weight and power wise, but suck reliability wise.", "People...learn the difference between wankel, rotary, and radial. OP clearly meant a wankel engine. The main benefits of a wankel engine are size, weight, and RPM. If you look at Formula One cars, they have piston engines that generally don't produce much torque...but they run at ludicrous RPM ranges with very short piston strokes. At those high RPMs you develop significant power. A wankel engine takes advantage of the same mathematics there. A traditional car engine has reciprocating mass. Pistons, piston rings, wrist pins, and connecting rod all reciprocate back and forth inside the cylinder at high RPM and generate enormous inertial forces while it accelerates, decelerates, stops, accelerates the opposite direction, decelerates, stops, accelerates back the other direction...etc. In rotating objects, Power = Torque X Angular Velocity. You can interpret that as Power = Torque X RPM. There are some conversions required to get the units to match up properly, but the fundamental relationship is true. If you're trying to make a more powerful engine you can either increase the RPM it runs at, or increase the torque it produces. For torque you can either use more force (i.e. turbo chargers, superchargers, nitrous) by making the combustion reaction more powerful, or by lengthening your connecting rods and stroke to give the piston more mechanical advantage. Back in the early days of piston engines, designers prioritized torque. Massive pistons, huge connecting rods, very high forces to drive things like tractors or industrial machinery. The problem is that they ran fairly slow and were huge. A 100 year old farm tractor had lots of torque but surprisingly little power because its engine turns so slowly. Modern engineers prioritize RPM. It saves on materials, decreases some forces (increases others) and makes engines more compact and light weight. We design engines with less torque, but significantly higher RPM to generate more total power, and then use transmissions and gear boxes to convert that power into high amounts of torque through gear reduction. It's a far more practical approach. The rotary or wankel engine you're asking about gets its magic from zero reciprocating mass. The crankshaft is balanced perfectly and can rotate at far higher RPM than a traditional piston-driven engine without tearing itself apart. That means that even if it has a little less torque, it'll generate lots of power because you can safely get the RPM very high. As others have mentioned they're difficult to maintain and have a few key components that are prone to wear and if those components fail it'll destroy the engine. They're also a little costly to produce. Getting a smooth and perfect cylinder wall in a V-8 is easier from a machining perspective than creating the smooth curved geometry of wankel engine components." ], "score": [ 5, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "glmu3ui" ], "text": [ "Plasma is a high-energy state of matter, it's not an energy source. You still need fuel from somewhere to create the plasma. Ion thrusters, which are fairly common on modern satellites, do use plasma as the propellant but they get their energy from solar panels to accelerate the propellant. In chemical rockets it gets blurry because the fuel (and oxydizer) are also the propellant, but it doesn't have to be that way. Fuel = place you're getting energy, propellant = thing you're throwing out the back of the rocket to make thrust. It's possible to use plasma for propellant but not fuel (using today's technology). We don't have any good ways to store plasma for long periods of time." ], "score": [ 10 ], "text_urls": [ [] ] }

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{ "a_id": [ "glmwmwq", "glmvw7g", "glmwofw", "glmynic" ], "text": [ "The sail acts like an airplane wing, moving air flows faster over one side of the sail, making a difference in pressure, and thus a force, pushing your boat along. If there's no wind at all, you're sort of SOL and just have to wait if you don't have a backup propeller. Your second question has an interesting answer that's called [tacking]( URL_0 . Basically you're using that pressure differential thing I said before, and if you angle your sail correctly, you can make progress to go upwind.", "Yes, losing wind makes for slow sailing. But all is not lost! On a small sailboat (dinghy sailors) you can “skull” where you move the rudder back and forth vigorously. This works like fish moving it’s tail to swim. You can also rock the boat back and forth which pumps the mainsail as well. (kinetic sailing) You’ll be surprised how much motion you can get with zero breeze. Larger sailboats have engines. World cruising sailboat tend to have more robust engines, with back up parts for repairs underway, and sometimes full workshops down below. Then again there are always an old salt or two out there, making the world their bitch with no motor, no fridge, a bottle of rum and a pack of saltines. To each their own.", "> How do they work? The resulting force of the two forces wind (pressing against the sails) and water (pressing against keel and rudder) propels the craft forward. Wind force is exerted perpendicular to the sail cloth and water resistance is exerted perpendicular to keel and rudder. > What do you do if you're out in the middle of the ocean, and the wind stops. The boat lies becalmed and cannot move. It will have to rely on having enough provisions and time, a motor or a way to call for assistance. > Or worse, having a wind blowing south, but you're trying to head north. Witchcraft? You cannot sail directly into the wind. You will have to \"beat\" into it, i.e. continuously change your course from northwest to northeast and back.", "As far as how the work? More like an ELI10, but... The science of sailing is the same as the science of flying. A sailboat just does so sideways, half submerged in water. Following? Good! Planes fly through air - their wings are equal size - because they have to be the same strength as they have the same forces applied to them as the plane flies. Boats “fly” though half air (low density) and half water (higher density) so their “wings” are different sizes because one has to be stronger than the other. (Harder to flap your arms in water than air, right?) The Sail and keel are the “wings” of a boat. The sail is big and floppy because the air it flows through is very light. The keel is smaller, rigid and stronger because it flows through they heavier water. These two pieces on a boat are designed to be in balance of each other though - which many may not realize. The rudder (controlled by the driver of the boat) operates the same as the flaps on a plane. (In combination with adjusting your sails) When we turn the rudder and adjust to the wind changes - we are actually “lifting” and “coming down” similar to how a plan does with their flaps. Sailboats never sail directly into the wind, or directly down wind. We need an angle on the breeze to make the boat go and safely. You may have heard the old joke that sailors never point the boat in the direction they want to go? That’s often true! Until we turn engine on. Then we are just another power boat." ], "score": [ 9, 6, 5, 4 ], "text_urls": [ [ "https://en.m.wikipedia.org/wiki/Tacking_(sailing)" ], [], [], [] ] }

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{ "a_id": [ "glrnxx3" ], "text": [ "Another question: Does people in US only (or majority) drinks water from bottles? Or this just happens on movies?" ], "score": [ 5 ], "text_urls": [ [] ] }

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{ "a_id": [ "glszg8k", "glszhn8", "glsz946", "glt4j0c" ], "text": [ "Electric car drivetrains are far more simple. There's a spinning electric motor, some gears, and wheels. The only thing that could go wrong is some bearings or gears going bad, and that sort of thing doesn't happen very often even in normal cars. The electric motor needs no maintenance ever. Internal combustion engines have dozens of small complex moving parts that all wear out over time.", "Piston internal combustion engines are extremely fickle, fragile, complicated pieces of machinery. The whole system is just a big giant block of moving pieces, belts, valves, gaskets, and cranks. There's about a million things that can go wrong, and it takes a lot of effort and money to go fix those things when they do go wrong. The vast majority of things that break in a car is related to all of those parts and pieces. If you can get rid of the piston engine inside of a car then 99% of your potential problems go away. Electric motors are, by comparison, much simpler, more reliable, and easier to work on. I certainly wouldn't say that auto mechanics would go away entirely, but they should certainly have less to do.", "So there are still things like suspension, tires, etc But a lot of maintenance work on ICE cars is due to the engine, transmission, exhaust, etc. Electric cars don’t have any of these components.", "A car on average has somewhere in the region of 20-30,000 parts. Depending on model, who you ask, etc. Most of those parts will be in the engine and engine bay. And those parts in the engine bay are heated up to boiling or well beyond boiling temperature and spun around at 100mph by hundreds of explosions every second. And it will be exposed to this for tens of thousands of hours over the life of a car." ], "score": [ 16, 6, 5, 5 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gltmzlt", "glth6l4" ], "text": [ "A compiler (or interpreter) breaks down each high-level function into a series of low-level functions. So \"X = 2*3\" becomes \"Write 2 to register A. Write 3 to Register B. Multiply. Write value of output register to memory address designated 'X.'\"", "They use a pre-existing program that knows how to translate the high-level source code into machine code, either directly or with some sort of intervening layer of abstraction. Sometimes they do this ahead of time (compiling) and sometimes they do it as they're executing code (interpreting)." ], "score": [ 13, 8 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "glxg0c6" ], "text": [ "They don’t. The only earth quake PROOF buildings are built into the ground and aren’t standing above it. The way they make them earth quake resistant is by making them flexible rather than rigid which is what you might think. A rigid building would crumble apart if shaken but a flexible one would move with the earth and compensate for its movements." ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "glz9s7y", "glz9qsf", "glzsgx5" ], "text": [ "Momentum! Train carts are very heavy, so a little bit of movement makes A LOT of momentum. Between each train cart is a connector called a 'coupling '. The important thing is that the coupling isn't a rigid connection between each side, but instead has a bit of room to move. So when the locomotive first takes off, it's just moving the engine. It'll move a few centimetres and then go ker-CHUNK and engage the first coupling, so the momentum of the engine gets split between the first two carts, and so they have a few centimeters to get some speed. So now there are two carts moving. And they move a little and go ker-CHUNK. The momentum of the two moving carts is much greater than the next cart, so their momentum is split between the three carts and are able to pull it even easier than the previous one, and then again and again and again. So the locomotive engine really only has to start pulling one cart at a time to start picking up speed.", "In addition to the amount of torque and power that train engines produce, there’s also very little friction between the wheels and the rails. This significantly reduces the amount of energy needed to move the train compared to other forms of transport. [This]( URL_0 ) video from Engineering Explained goes into detail about why that it is and how much of a difference it makes.", "In addition to some of what has been described here so far, one of the key features of modern locomotives is that the powerful diesel engines are often diesel-electric or diesel-hydraulic. That means the diesel engine isn't turning a crankshaft that's coupled to the wheels via shafts or gears. They use the diesel to generate electricity and have electric traction motors that turn the wheels, or use hydraulics (much like how an excavator or tank operates...combustion engine driving a hydraulic motor)." ], "score": [ 27, 10, 3 ], "text_urls": [ [], [ "https://youtu.be/Au3U72CX74I" ], [] ] }

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{ "a_id": [ "gm2ybu9", "gm3hw0e" ], "text": [ "In general, coarse threads are easier to start and faster to screw in, while fine threads are stronger for a given base diameter. Having two options as widely available, standardized choices for each screw diameter allows engineers to pick a thread pitch which is most useful in the particular application they are designing for.", "Fine thread is more sensitive to damage, and requires more precision during manufacturing. It also takes more time to screw something on/in. Coarse thread is good enough for most applications. Engineering isn't the art of finding out what works; it's the art of finding out what works just well enough" ], "score": [ 26, 7 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gm3kvz6", "gm4u6ld" ], "text": [ "Because they drive on different sides of the road. The steering wheel is positioned to give the driver the best view of oncoming traffic.", "In Great Britain, they drive on the left because historically, they rode horses and they needed to keep their right arm free to wield their sword against oncoming traffic. In the US, they drove on the right because wagons didn't have a driver's seat -- drivers sat on the rearmost left horse. And the reason they sat on the left so that they could use their right arm to crack their whip over both of the lead horses." ], "score": [ 7, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gm44loh" ], "text": [ "There are a few advantages to stif suspension on a race car. For example when you go around a corner a lot of the weight is put on the outside wheels. If you have soft suspension then the suspension on the outside wheels will get shorter as it gets loaded and the suspension on the inside wheels will get longer as it gets unloaded. This means that the entire body rolls over to the outside putting even more weight on the outside wheels. This means that there are a lot more forces going through the outside wheels and almost no forces through the inside wheels and it is therefore more likely for the outside wheels to lose grip causing the car to slide. And in the worst case the inside wheels may get completely unloaded and the car may roll over on its side. Another reason you might want stif suspension is so you are able to get the chassis of the car as close to the ground as possible exploiting the ground effect for aerodynamic benefits which allows you to go faster through the corners. A softer suspension might cause the chassis to hit the ground during manouvers which reduces the downforce to almost nothing and unloads the wheels reducing the friction forces you can get out of them. It also improves handling in general as the suspension geometry does not change much depending on the forces put on them. But there are also disadvantages to a stif suspension. In straights you do not want downforce as it creates drag and reduce your top speed so a softer can help you raise the car on the straights and then create the optimal downforce geometry as you slow down towards a corner. Also if you have bumps in the track a stif suspension will cause the wheels to lift off the ground in the bumps and you lose traction while a soft suspension can help the wheel mantain contact and you get more traction. So different tracks will usually have different optimal suspension settings and finding the right setting for the track in the current conditions is very important to winning the races." ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gm5b8dq" ], "text": [ "I know this one! The lip gives the end of the balloon more thickness and support. That way the end can be blown up with your mouth or placed over the end of a filling tube easily. Next time you have a balloon cut off that lip and see how difficult it is to put air into it. The lip is made by rolling the end of the balloon down over itself during the manufacturing process. It's kinda like rolling your sock down to your ankle." ], "score": [ 10 ], "text_urls": [ [] ] }

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{ "a_id": [ "gm5esjo" ], "text": [ "It’s about both convention, convenience, and manufacturability. You can certainly find examples of aluminum bottles. Cans of the past shaped differently than cans of the present. Typically bottles will be in the shape of bottles and cans in the shape of cans. You can read about the history of the coca cola bottle shape here URL_0" ], "score": [ 4 ], "text_urls": [ [ "https://www.coca-colacompany.com/company/history/the-history-of-the-coca-cola-contour-bottle" ] ] }

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{ "a_id": [ "gm6ga74" ], "text": [ "In really simple terms, it’s a grate that goes over the opening of the faucet. When water comes out quickly, the little bars on the grate leaves gaps between the many tiny streams of water that come out of the holes, which allows air to get in and breaks up the stream of water coming out of the faucet. If it comes out slowly, the water can quickly recombine into a single stream, which is why turning it on low tends to give you a single clear stream of water instead of the fast foamy flow when you turn it on full blast." ], "score": [ 9 ], "text_urls": [ [] ] }

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{ "a_id": [ "gm75e3t", "gm75y16" ], "text": [ "Every force exerted on something has that same force exerted back on it. Shooting a projectile one direction makes the gun (or cannon) want to move the other way. This could damage the mechanism or hurt/kill the people behind the piece of equipment. Why not design something that has 'give', a system in place to disperse or redirect that force. That is the *controlled* recoil you're talking about. Also, use less gunpowder? These are devices used to deliver kinetic energy, in a destructive way, across distances. Making them less effective on purpose kinda defeats the point.", "You're right that the recoil is energy taken from the charge, but it's \\*not\\* true that much of that energy could otherwise go into the shell. Having large recoil greatly lowers the peak load on the cannon (for whatever amount of charge you put in) and doesn't really do anything that meaningful to the shell. When the charge goes off, you \"instantly\" crank the pressure in the bore up to something very high (thousands of psi). This pushes forward on the shell and backwards on the breech with equal force. The forward force on the shell accelerates it down the barrel, the backwards force on the breech needs to be reacted into the cannon mount. If you allow recoil, the breech can slide smoothly backwards...and temporarily store some energy in the recoil mechanism, lowering the peak load the cannon mount. If you don't allow recoil, you have to send all that force straight through to the cannon mount (and it's a really sharp load, likely to fatigue and break things much faster). The fact of recoil makes the barrel look a little bit shorter to the projectile than it otherwise would, so you are losing a little drive but it's at the end of the barrel where the driving force is already lowest. You can counteract that by making the barrel just a bit longer (it would never need to be longer than the recoil stroke). You also get slightly more expansion of the gas by virtue of the breech moving back, so the pressure is a little lower, but the recoil stroke is typically much smaller than the barrel length so, again, this isn't a major factor to the projectile. The recoil may actually allow you to add \\*more\\* charge, since the mount can handle more breech pressure, and get more overall projectile velocity." ], "score": [ 12, 7 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gm7ew4a" ], "text": [ "The whole filling system is under pressure, so the CO2 stays in the soda.. Befor filling - the bottle is also set under pressure. The filling process is separated in 4 phases: compress, fast filling, slow filling, decompress. Decompressing is a step where the bottle is decompressed slowly to prevent foaming. I hope you get the point, english isnt my first language and don't know all the right terms yet. If you want to see it - search on youtube for PET Filling. Companies like KHS, Krones, Sidel should have Videos to this. You may find it interesting." ], "score": [ 19 ], "text_urls": [ [] ] }

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{ "a_id": [ "gm84l02" ], "text": [ "A PID controller is made up of 3 parts. Proportional Intergral Derivative You then have a target value you want the system achieve and maintain. The distance from that target value is your error. For example if you want a car to drive at 100kph but it’s currently moving at 90kph then the target value is 100 and the error is 10. The proportional part of the controller works as hard to fix the error as the error is big. Meaning if the error is twice as big it’ll work twice as hard to fix it, if the error is half as big it’ll work half has hard to fix it. In the case if the car analogy it’ll work 10 hard to fix the error as the error is 10. The integral part of the controller is similar to the proportional part, but it also has a time component. So the longer an error lasts for the harder the integral part of the controller tries to fix it. Going back to the car analogy working 10 hard to fix the error might not be enough to fix it if the car is going up a hill, but if the error doesn’t get fixed quickly the integral part of controller will realise this and work harder to fix the error. So for example initially it’ll be working 10 hard to fix the error (from the proportional) but after 1 second it’ll be working 11 hard, after 2 seconds it’ll be 12 hard, etc. The derivative part is designed to control how fast the error is being corrected. If the error is being corrected too quickly then it can overshoot the target value. Back to the car, imagine you’re going 90 and the car then decides to go to full power, you’ll go past 100 where it then has to slow down again, but if it slows too fast it’ll drop below 100 and has to speed up, then it goes past 100 and has to slow down, etc." ], "score": [ 9 ], "text_urls": [ [] ] }

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{ "a_id": [ "gm8ltkq", "gm8nv55", "gm8ogfj" ], "text": [ "For a bicycle you are turning a single very narrow wheel without much weight on it. With a car you’re turning a very heavy object with a two much wider contact patches.", "When cars were made without power steering, they had huge wheels, which had to be turned multiple times to reach full lock. This means they had a mechanical advantage both from the leverage of the wheel, but also from the gearing of the steering column to the wheel rack. Once power steering was invented, this no longer needed to be done, the power advantage was done through motors, not design of the wheel. This meant that the steering wheel could be made smaller, making it easier to fit your legs under. Also you could reach lock in a turn and a half, rather than a few turns, making steering quicker and more responsive. But these advantages only worked AF power steering was functional. As soon as the power steering broke down, you are WAY worse off than before it’s invention. Not only do you have a small wheel, and a high gear ratio on the steering column, you also have much heavier vehicles. So modern vehicles are hard to steer without power steering because everything on their design has been based on the assumption you have it. Without it, the car doesn’t function as designed!", "What everybody else said about friction isn't wrong, mechanical steering is heavy but it gets easier to turn when the car is moving, in the case of assisted direction it gets even heavier if you pump or the electric motor aren't moving, that's because now the mechanism design to help you steer is adding to the friction on the floor. If you ever tried to move an electric motor by hand you must've noticed that it tends to resist the motion, that makes the steering wheel heavier" ], "score": [ 6, 4, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gmbcm86" ], "text": [ "Generally speaking? Heavy equipment and levels. More specifically, bulldozers/earth movers rely on either GPS equipment or human surveyors to check the elevation (height) of the land. The old fashioned way involved a sight level (basically a gun scope that's set to be perfectly flat) and a big ruler on a stick. The surveyor would look at the ruler set on a known height (let's call it '10'). The guy with the big ruler walks around and the guy with the scope looks at the numbers. If he sees '11' in one spot, it means that they need to add a foot of dirt. If he sees '9' in a different spot, it means they need take away a foot of dirt. If they're using a gps system, then satellites and/or computers do all work. Some high end equipment uses sensors set to each side of the bulldozer blade and automatically adjusts the equipment to be within a few millimeters." ], "score": [ 8 ], "text_urls": [ [] ] }

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{ "a_id": [ "gmbsej0" ], "text": [ "For analog stuff (1.5mm, 3mm, etc) it's due to smaller devices needing smaller jacks at the cost of audio fidelity (way back in the day of all analog, now all of the different ones are more or less the same quality). Or nowadays optical cables are used for super far distances with no interference For digital stuff (lightning, USB, etc) it's more difficult to explain. For example, Lightning for Apple's stuff is due to them depreciating the 3mm jack but customers still wanting wired earbuds. MIDI is actually not audio per se, it's used to send MIDI data which by itself is a standard digital signal that's used mostly for audio purposes (usually keys on a keyboard being played so it can be recorded and edited)" ], "score": [ 5 ], "text_urls": [ [] ] }

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{ "a_id": [ "gmjl3aw", "gmjl434" ], "text": [ "Quartz vibrates bzzzzz at a consistent rate when electricity is applied. We know how many bzzzzz per second and then use that calculation for maintaining time on a quartz watch.", "Quartz is a type of mineral. When electricity passes through it, it vibrates at a predictable frequency and those vibrations can be measured in a way that you can get precision timing from it. It vibrates 32,768 times per second." ], "score": [ 7, 5 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gmlojji", "gmlp68z", "gmlp0l9", "gmlsa30" ], "text": [ "Answer. You don't sail directly into the wind, you sail across it. Imagine the wind is blowing due East. If you set your sails correctly, and steer, you can go North and slightly West. After a while you re-rig the ship and go South and slightly West. It takes a long time and a lot of work. That's why it was easier to sail down to the Equator, where the 'Trade Winds' blow east and west.", "The sails do not always have to be at a right angle to the hull. Even square rigged sails have the ability to turn around on the mast. So even if the wind is coming from a forward direction they can turn the sails to be able to catch the wind.", "> Everything that I've read online sais that they could sail something like 67 degrees sharp into the wind That does not necessarily apply to square-rigged sails. Tightly close-hauled sailing is really only possible with (at least *some*) Bermuda-rigging. How close to the wind you can sail with only square-rigged sails depends on the amount/angle of rotation you can perform with the spars. Edit: Have a look at [this]( URL_0 ) mostly square-rigged ship tacking.", "You are correct that a square sail is far more limited on its point of sail and can't sail as close to the wind, its better suited for running This is why even \"[square-rigged]( URL_0 )\" ships had triangular bow sails (jibs and spankers) that would help them sail close to the wind. The sails on the bow could catch the wind coming from the side of the boat which pushes the boat mainly sideways(cancelled out by the keel) but also slightly forward, this isn't nearly as fast as running with the wind 30 degrees off of port but most of these ships were super slow anyway. The HMS Victory was quite fast for its era at 11 knots (20 kph) so even if the triangular sails can only move it at 2 knots that's not awful." ], "score": [ 22, 6, 6, 3 ], "text_urls": [ [], [], [ "https://www.youtube.com/watch?v=BxCKGS_bLKI&list=PLefH9tOAGIfYNwHSEz7Yr43njqltX-EsL&index=15" ], [ "https://upload.wikimedia.org/wikipedia/commons/thumb/5/5d/Sail_plan_ship.svg/1024px-Sail_plan_ship.svg.png" ] ] }

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{ "a_id": [ "gmmap1s", "gmmcvxb" ], "text": [ "Engines get hot no matter the weather so the heater pulls air from the engine compartment. That's also why it may take a couple of minutes to get hot air when you start up the car. The engine is still cold.", "A car's heater is a radiator, it pumps very hot engine coolant through a small radiator with of pipes and hundreds of tiny fins, which makes the fins quickly get very hot. It then passes the cold air through the fins. The fins have a very high surface area, so they can heat air quickly as it passes over them. [Here's]( URL_0 ) a picture of the inside. The tubes at the bottom are for coolant flow in and out." ], "score": [ 7, 3 ], "text_urls": [ [], [ "https://images-na.ssl-images-amazon.com/images/I/614sG-DtfDL._AC_SL1001_.jpg" ] ] }

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{ "a_id": [ "gmoiv7r" ], "text": [ "It's a circuit of Capacitors and Induction coils used to smooth the current and voltage. A capacity prevents voltage from changing too quickly, inductivity prevents currents from changing too quickly. If you combine both you force both to take a sinus wave shape because current and voltage switch between both (stored as electrical or magnetic fields) By designing the size of both and connecting them in specific ways you can decide how fast voltage and current can change to filter out frequencies you don't want." ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gmptc5k", "gmq1fan" ], "text": [ "Older systems couldn't rely upon always being connected to other computers. They would have to dial a phone to connect with another bulletin board server and exchange messages. They often only had one phone line and couldn't have a user signed in at the same time.", "You are mixing a couple of ideas. Time-sharing computers used terminals that, if you looked at them, look exactly like a modern PC but they were wired directly to what you would think of as a mainframe. So you would type commands into a terminal and basically wait for your turn to have your commands processed by a central computer. Back in the late 70s and 80s, if you were trying to run your program on a university computer you better be sure it could run in your allotted time otherwise it would cut you off mid-execution. This isn't really a network since the terminal itself, while connected over phone lines, wasn't an independent computer. As PCs became less expensive, the protocols to link *independent* computers became more widely available. This was still before the 'modern' internet because you still dialed directly to another computer to do whatever you had to do, the most common example is doing a file transport protocol. Your buddy at a different university wanted to see your program code so you dialed into his computer and uploaded the text to his/her computer for them to look at. We typically think of the 'modern' internet as being when the first widely available web browser was available and we standardized on the HTTP protocol for websites. For nerds we would say it was actually when BGP was standardized a few years earlier in 1989. Before BGP was standardized you had to do a lot more work to get to a different 'autonomous system', if the computer you wanted to connect to wasn't on the same local network of computers as you that required more coordination. With BGP it was automated." ], "score": [ 8, 6 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gmr3qq4", "gmr48wv", "gmr3l4f", "gmr4pmz", "gmr4fws" ], "text": [ "The energy required to chamber a new round is very small, and this is verifiable as semiautomatic weapons don't lose any significant energy compared to their manual counterparts. It's difficult to describe just how little energy it takes, though a semiautomatic weapon would lose some small amount of muzzle energy compared to a bolt. This doesn't really reduce its effectiveness - a slightly slower bullet doesn't make somebody any less dead. It is also worth note that the energy is often extracted from the gas near the end of the barrel, meaning that this energy would never have gone to the bullet.", "No. The amount of energy used to cycle the gun is utterly insignificant to the amount of energy imparted on the bullet. Similarly, a fixed barrel in a rigid mount isn't any more powerful than a gun that experiences recoil, not in any appreciable way. You can find more variation with your ammunition alone than you will be able to measure between firing in these different scenarios.", "A portion of the recoil force that would otherwise go into your shoulder is used to kick back the bolt. There is a split between that and reduced projectile velocity, but by no means enough to consider a bolt action superior in force of impact.", "With what you're talking about, it's like the difference between getting hit by a car going 60mph vs getting hit by a car going 59.99mph. Yes, there is a slight difference in power but not nearly enough to have a substantive effect on the outcome.", "It is not much more powerful, but a bit. The amount of energy it takes to cycle the bolt is very small compared to how much energy the bullet have when it leaves the barrel. So you do not reduce the speed of the bullet by much by making the gun cycle automatically. In addition to this it is very hard for a gun to use all the energy in the gunpowder to accelerate the bullet. A lot of the energy that is used to cycle the gun is energy which would otherwise not get used in any way. In fact there are automatically loading rifles which only use excess energy and does not reduce the speed of the bullet at all. That being said not all rifles are able to get the same amount of energy from the same cartridge. For example if the barrel is too short or too long the bullet will be slower then if the barrel is exactly the right length. Some guns do not have a properly sealed breach and will vent gas out the back which could have been used to propel the bullet forward. This applies to all but a few exceptional revolvers in addition to some automatic pistols. But the type of automatic rifle such as the AK47, G3 or AR15 does not significantly slow down the bullet in order to run the rifle." ], "score": [ 14, 8, 5, 5, 3 ], "text_urls": [ [], [], [], [], [] ] }

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{ "a_id": [ "gmsrgn8" ], "text": [ "If it was on the mac app store, google would have to build it to a specific standard set by apple" ], "score": [ 5 ], "text_urls": [ [] ] }

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{ "a_id": [ "gmthmh8" ], "text": [ "It's pretty wide at it's base, 90' x 90' I believe. And all concrete as well. With enough internal shear walls placed correctly, it can be very stable. These are thick concrete walls that are places parallel to the way the building would tilt, to prevent the building from tilting. Acompanied by structural elevator cores, which act as shear walls in two directions, the towers are surprisingly sturdy. That being said, all towers sway, some more than others. Apparently you can feel the sway at 432 park, but also in a few of the other tall towers in the city. One of the problems the tower faces at the moment, however, is that the interior construction didn't account for the sway so much, so there's audible creaking in the tower from ductwork, long chases, etc. I'll be curious when the new tower at 111 w 57th goes up. If I'm not wrong the footprint is 40x60 at nearly 1400 feet, whereas I believe 432 park is only 1000." ], "score": [ 4 ], "text_urls": [ [] ] }

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{ "a_id": [ "gmug6vv", "gmvqlhi" ], "text": [ "Without suspending in water, a lot of it will break in transportation. If you try to stack tofu outside water, the bottom layer gets crushed very easily.", "I believe pressing tofu is something western people came up with to make the tofu tougher, more meatlike and easier to flavor/marinade. Pressing the tofu is not a thing in traditional asian cuisine as it's treated as its own thing and not trying to be a meat substitute (in fact dishes like [\"mapo tofu\"]( URL_0 ) serve tofu alongside meat)." ], "score": [ 48, 7 ], "text_urls": [ [], [ "https://en.wikipedia.org/wiki/Mapo_tofu" ] ] }

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{ "a_id": [ "gmv1jfk" ], "text": [ "It's a time delay door switch, meaning it takes a second or 2 before it opens up and de-energize. About the same time to open and throw something in quickly" ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gmv5343" ], "text": [ "power doesn't have to be EXACTLY 50 or 60 hz, it just has to AVERAGE 50 or 60 hz. If you monitor the frequency of the power in your (US) house you will notice that at times it is above 60 hz, (ie, 60.35 hz) and other times it'll be below 60 hz (ie 59.65 hz). When you're generating power, and everything is in balance (load equals generation) the Generator RPM will be consistent, (generally 3600rpm). BUT if you suddenly stop drawing power from the system the resistance isn't there an the generator will speed up, increasing the frequency on the line. Grid deals with this by having very large systems, spread around, so that at any one time it's very unlikely that a significant portion of a single plant's load will be disconnected suddenly. They also have very precise controls so that if the generator RPM starts to increase they can cut back on the driving power to the generator (steam, or hydro, etc), and if the RPM increases too much the system will cut off that generator from the grid and shut it down. The same goes for RPM dipping too low, other than a generator can't put out more than the input driving force you give it. If you are pulling too much for a generator to handle you need to either drop some load, or bring another generator online. A single house shutting off it's breakers will not affect the power station significantly. A single block might affect them slightly. An entire industrial complex suddenly shutting down, yeah that affects them quite a bit." ], "score": [ 5 ], "text_urls": [ [] ] }

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{ "a_id": [ "gmwauu8", "gmvxuy5", "gmw8f0k" ], "text": [ "A lot of people are talking about different programming \"languages\" but that's not actually the core problem with consoles. Until relatively recently, game consoles were not general purpose machines like the computer on your desk. They were very special, custom pieces of hardware, and they had very little in common from one generation to the next. This means regardless of what \"language\" we used, we had to write the code in a very specific way that we knew the target console could understand and run, which was a really quite limited set of instructions that was sometimes very different per console. Say that you have a dog that was originally trained by someone who speaks Spanish. You do not. Provided you could find someone to translate your English into Spanish commands for the dog, you could probably get the dog to \"sit.\" But now instead of a dog, you have a parrot. It doesn't matter if the parrot speaks Spanish. It doesn't matter if you have an English to Spanish translator. The parrot simply does not understand the command \"sit\" in any language.", "The old game is like a book written in a language the new console doesn't understand. When a game is ported, the programmers write a new book that tells the console how to translate the old book. They give the new console both books. edit: u/Xeelef is right, I was thinking of emulation!", "They don't have to start from scratch, but they do have to re-do a bunch of work. The new system will typically have wildly different hardware from the old one, so they have to rewrite a lot of the code that pertains to how the game uses the system's hardware - e.g. what various control inputs do, how to draw everything on the screen, how to play the sounds and music. Let's call that the \"low level\" sections of the software code. But then, a lot of \"high level\" sections of software code – like how the player interacts with characters, swings their sword, etc. – don't have to be changed, because they're just communicating with the low-level code rather than directly communicating with the system's hardware." ], "score": [ 7, 3, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gmwkoua", "gmwk5ak" ], "text": [ "Imagine you have a car. But this car is only driven by professionals who have to train on simulators and renew their licenses to drive every year, and your car has two drivers at all times. And so do all the other cars, but there’s never any other cars nearby. There are people in a nearby building tracking every single car and making sure they don’t get close to each other. And all the cars have at least two engines, and those engines are super-reliable turbines that cost millions of dollars each and are remotely monitored for performance and are always serviced by a team of specialists right on time, as is the rest of the car. And all the critical systems are redundant. And the cars drive in a place where there is literally nothing to hit for many miles around, including above and below it. And every time a car does crash, even a fender-bender, a team of experts investigates every aspect of it and makes fixes to the whole system so it doesn’t happen again. That’s commercial flying.", "Because if you compare the number of people every year who travel by airplane to the number of people injured or killed it is far safer than cars. It does make me wonder why trains aren't the safest because train trashes don't happen that often, but the point is airplanes are FAAAR safer than cars." ], "score": [ 21, 5 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gmxg8i0", "gmxfp17" ], "text": [ "When you tape the outside of the boxes, you're using the tensile strength of the tape. When you tape the inside, you're using the strength of the adhesive, and the tape may peel away from the cardboard.", "Its about the push/pull resistance and support. If you tape on the outside of the box it supports the way the box was folded in. If you taped on the inside the the flaps would push down/out from the weight and separate from the tape.j" ], "score": [ 15, 4 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gmzhj3w", "gmzf7gg", "gmzecoc", "gmzexz6" ], "text": [ "In the case of highways, it’s sensible to balance out what’s called the cut/fill. For example, you can cut through a small hill, and use that material to fill a small valley. Which in turn gives you a flat road to drive on. By re-using all the material excavated instead of taking it off-site, means it might be more cost effective to have a slightly longer curved road which is in balance. Than a straight road that was all in cut. For a mountain road, there is still a certain amount of cut to fill, but more of a focus on following an easier gradient to drive up.", "When building roads around a mountain, the easiest, cheapest way to build that road is to follow the path of the mountain - building a straight road might involve a lot of demolition (which is expensive and difficult), or it might involve a very steep slope, which causes its own problems, especially with large trucks. Following the mountain's curve and only having a slight slope typically ends up being safer and more efficient, since cars don't have a problem following curves like trains do. As for highways and such, they're either following local geography or they're avoiding other current property. If the government wanted to build a new freeway, for example, they'd have to buy all of the land to build that freeway on - and it's often cheaper to curve around properties than try to buy them and demolish them to make room for the straight path. Once you get outside of major cities and into relatively flat land, roads tend to get much straighter, because they can follow a simple path and other people's property is more spread out.", "Because they have to go around private properties, obstacles, terrain and avoid too steep gradients. When there is none of the above, roads are straight (for example deserts or plains in the US) (sometimes the state can buy properties to build straighter roads such as motorways)", "You might not notice it if you are used to driving modern cars with lots of power. However if you have driven older cars or fully loaded trucks that only just have enough power to go highway speeds you might have noticed how much more power is required to climb even a small hill rather then drive around it. So roads will try as far as they can to stay in the same level in the terrain even if this means having a lot of curves to go around all the small hills and dumps in the terrain." ], "score": [ 9, 6, 3, 3 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gmzpj38", "gmzt3wi" ], "text": [ "Battery voltage drops over time. Depending on the battery chemistry (lead-acid, lithium polymer, nickel cadmium, lithium silicone and cobalt or iron disulfide, etc.) that curve can be gradual and resort in diminished performance over time, or it can be quite rapid and result in 100% power output and suddenly dropping to zero. Some battery monitoring devices just look at the instantaneous battery voltage and compare that to what the expected values are, and readout a battery percentage. Others can actually measure the output current and voltage and compare that back to the battery's capacity at full-charge to get a feel for how much energy has been depleted. There are some proprietary techniques out there too. Certainly the most common is just measuring the battery's voltage.", "There are some devices that track power usage over time -- for example, the [Psion Series 3]( URL_0 ) palmtop computer from the 90s [did not include a voltage sensor]( URL_1 ), because of the added cost and circuit board space required at the time. So, engineers measured the power consumption of a bunch of test devices, and then programmed those as estimates into software. However, for modern devices the cost and complexity of adding a voltage sensor is very very small -- so that's by far the most common approach." ], "score": [ 9, 3 ], "text_urls": [ [], [ "https://en.wikipedia.org/wiki/Psion_Series_3", "https://www.opennet.ru/docs/FAQ/hardware/palmtop-psion/series3-part2.html" ] ] }

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{ "a_id": [ "gn0hfgl", "gn0i6qu" ], "text": [ "I had this same question! A helpful optometrist explained it along the lines of- Your eyeballs aren't really spherical, the lens over your pupil makes it kind of poke out. So, it's less like trying to hold a paper plate against a basketball, which would slip all over, and more like putting a party hat on a football, so it kind of wants to sit there and even if you bop it around a little it'll settle back where it was.", "Your eyeball isn’t actually uniformly spherical. The cornea, where the contact lens sits, bulges out a little bit, meaning that the curvature of the area where the contact lens sits is different than the curvature of the rest of the eye. The contact lens is sized to fit the curvature of the cornea, so in order to slide off the cornea the contact lens needs to either deform or pull away from the eye- either of which means that the cornea the “easiest” spot for the contact lens to remain." ], "score": [ 21, 8 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gn1ube0", "gn1ug57" ], "text": [ "There's a brake booster that sits in between the actual lever you press against when you hit the brakes and the hydraulic pistons that deliver braking power to the wheels. It uses vacuum from the engine intake system to basically preload a spring that helps you put more pressure on the brakes. So if your engine isn't running, it's not creating an intake vacuum, which means the booster has nothing to work with. That's a very simplified version. This is slightly better: URL_0", "There is a brake assist drum near the engine. It helps with braking by using the vacuum from the intake manifold of a running engine. If you look on this drum, which is located under the brake fluid reservoir, you'll see a tube connecting the drum to the intake manifold. If the engine isn't running, it doesnt't cause a vacuum, so there is no brake assist." ], "score": [ 10, 3 ], "text_urls": [ [ "https://www.youtube.com/watch?v=wbTUvp-tD5M" ], [] ] }

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{ "a_id": [ "gn5wns5", "gn79s2z", "gn82716" ], "text": [ "It depends what you want to shoot at. It is usually living targets. The thing with living targets is that a perfect but small hole wouldn't kill them. (Considering you don't hit some vital part). It is even better for survival to have clean heat-desinfected hole than stuck bullet inside your body. So how do you send a body to the ground fast and guaranteed? You use the impact force. And that's the thing with soft lead. It deforming means it is passing on all of the force it has. This way broader area of body gets impacted. If you wanted to shoot through metal plate, you may consider some better-shaped tip or some other material. Try researching different tank ammunition for reference. And finally if you wanted to shoot werewolf or other mythical beast, it's best to have bullets made out of silver.", "Two things: - Stronger metal will wear out barrel much faster than softer metal. And there are legal issues for bullets made of harder metal inside softer jacket/sabot, as those combinations are used for armour piercing bullets. - The denser bullet material is, the better its performance, and lead is cheapest high density material. Bullet made from other high density metals (like solid copper) are more expensive.", "Because you generally aren't shooting steel plates and when you are you do use some stronger. Lead is cheap, heavy and because its soft it won't go straight through a soft (flesh) target but deforms inside the target doing more damage. But if you are shooting at vehicles known to be armoured...well it's called armor penetrating rounds for a reason. They're usually a steel or tungsten core in a copper jacket." ], "score": [ 13, 4, 4 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gn71z75" ], "text": [ "As it chops things up there is less to chop and less resistance to the chopping so even though the motor is producing the same power the blades increase in speed." ], "score": [ 9 ], "text_urls": [ [] ] }

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{ "a_id": [ "gn858nc" ], "text": [ "Jets leave white trails, or contrails, in their wakes for the same reason you can sometimes see your breath. The hot, humid exhaust from jet engines mixes with the atmosphere, which at high altitude is of much lower vapor pressure and temperature than the exhaust gas. The water vapor contained in the jet exhaust condenses and may freeze, and this mixing process forms a cloud very similar to the one your hot breath makes on a cold day." ], "score": [ 7 ], "text_urls": [ [] ] }

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{ "a_id": [ "gn8q1ms", "gn905cs", "gn9634v" ], "text": [ "No modern bombs do not whistle. The Germans added the whistle to instill more terror on there bombing victims.", "Modern bombs, bombers, and all military aircraft are made with stealth in mind. You won't know a bomb has dropped until after it combusts or impacts the surface. It is essentially the loud noises emitted are a type of psychological warfare. The noise is meant to confuse and scare the crap out of you, and predictably make you run out of cover in order to increase chances of you actually being hit by the blast or spotted by an attacker. [Roman Whistling Ammunition]( URL_1 ) [Shaojian Whistling Arrow]( URL_2 ) [German Sturzkampfflugzeug Bombers]( URL_0 )", "those who say bombs don't whistle are not totally correct. small indirect fire weapons, called mortars, whistle as they fall from the sky. Any \"bomb\" that has its own propulsion and travels beyond the speed of sound will be totally silent to an observer the moment it hits the target" ], "score": [ 14, 11, 5 ], "text_urls": [ [], [ "https://nowiknow.com/the-sound-of-world-war-ii-planes/", "https://www.scientificamerican.com/article/whistling-sling-bullets-were-roman-troops-secret-weapon/", "https://mandarinmansion.com/glossary/shao-jian" ], [] ] }

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{ "a_id": [ "gn97s8a" ], "text": [ "Thats the mathematical description of state machines. There are finite, and infinite automatons, characterized by how many possible states they can be in. An automaton is defined by the function of wich state x_k and input u cause wich follow-up state x_k+1. Finite automatons are good to evaluate systems with known setups, like traffic lights, infinite state machines are more open ended and are a good approximation of computers (when you ignore a finite size memory) Any more specific questions? The topic is pretty broad." ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gna57k8", "gna6qnx", "gnbhzf7", "gnamuop", "gnac454" ], "text": [ "They do have solar farms like that, not whole deserts mind you, but between building and maintenance costs it can only work for certain places.", "We can but the main issue is energy storage. We could easily power cities during the day with just solar when there’s no clouds. But we need huge batteries to store the energy if you want solar energy at night. It’s hard to make batteries at that scale.", "Places like here in AZ many homes have roof panels. It’s closer to where the need is. Also don’t get me started on how totally screwed up the solar market is out here with subsidies from the government, and then getting charged a fee from your local provider for generating your own energy (looking at you, SRP)", "Somehow the ecosystem hasn't been mentioned at all. Deserts may appear void of life but they are full of it. People shouldn't just go an install 1000's of acres of panels for the sake of powering a city. Even if, you don't factor cost, transmission efficiency, energy storage, heat-losses and maintenance costs.", "1. Energy storage is expensive, solar has the issue that its highest output is not during the period of highest consumption. 2. Deserts while pretty great for solar panels sun-wise, have some issues regarding solar panels. First off, solar panels work best when cool. Second, they require maintenance, and not a lot of people want to live right next to massive solar farms in the middle of fucking nowhere." ], "score": [ 52, 13, 11, 10, 9 ], "text_urls": [ [], [], [], [], [] ] }

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{ "a_id": [ "gnf4etx", "gng5ul9", "gng39d5" ], "text": [ "It is both very simple and very complex. First, it can be helpful to know about an extremely simple type of old-fashioned film camera called a pinhole camera. A pinhole camera is simply a piece of film in a tightly sealed box. On the side of the box opposite of the film, there is a small pinhole that is covered. When you want to take a picture, you uncover the pinhole for a moment, the cover it again. You then take the camera to somewhere dark, remove the film, and develop it. (Developing film involves using chemicals to finish the film, to prevent additional light from damaging the image.) Then, you can look at the film to see the picture. However, you will notice that the picture is upside-down. The reason it is upside down is that the light travels from the light source, bounces off the thing your are photographing, then goes in all directions, but all of the rays, after they bounce off the thing, go in a straight line. Some of that bounced light goes toward the camera, and some of it goes into the pinhole. Each ray of light travels in that goes in can only hit one small part of the film. So, the light that bounces off your subject's foot has to go straight through the pinhole of the camera, and keeps going upward to hit the \"top\" of the film, and the light from the subject's head goes downward to get through the pinhole and hits the \"bottom\" of the film. Each individual part of the subject gets photographed on an individual part of the film. Something like this: HEAD \\ / FOOT BODY - * - BODY FOOT / \\ HEAD Now, you could get a new piece of film, and cut your film in half, put it in the pinhole camera and take your picture. You would end up with two halves of the picture. Then, you could put the two halves together and have the full picture. You could keep cutting it in half and in half again, to where you have hundreds of little squares of film, then put all those little squares in the pinhole camera. (You would have to be careful, and number the pieces, etc. Let us ignore that and just imagine it words as expected.) The light from the subject's toe would bounce off, and go through the pinhole to hit just the \"toe\" part of the film. The light from the subject's head would hit lots of pieces of film in the \"head\" area of the layout of all the little pieces. When you took all the little pieces and put them together, you will still end up with the same entire picture. Now, to get to the actual answer to your question. Replace the hundreds of little pieces of film in the previous step with hundreds of electronic sensors that can see light, and can tell the brightness or dimness of that light. Wire them all up so that each sensor is connected to one of hundreds of lightbulbs on a large board. The toe \"light\" will light up, but will be a slightly different amount than the space right next to it, which would be the shadow between it and the next toe. The \"head\" area of lights would light up, but would show the brightness of the nose and forehead, and the shadow of the eyes and under the nose. Blonde hair would show up brighter than darker hair, and so on. From that, you can get ever better sensors that are smaller, placed closer together, and replace your lightbulbs with smaller lightbulbs that are also closer together to get an even better picture. Lastly, you could replace each sensor with three sensors. Each \"first\" sensor would have a filter over it that only allowed red light through, but would still allow the sensor to detect the brightness of that red light. The second would have a green filter, and the third would have a red filter. On your board of lightbulbs, each bulb would be replaced by three bulbs, colored red, green, and blue. Now, the amount of red light coming from your subject's toe would hit the three \"toe\" sensors, but only the red sensor would see it. Same for green and blue. The board would light up the same combination of red, green, and blue, and you would get a replica of the toe's color. You could then take that setup, and replace the board of lightbulbs with a digitizer that records the values of red, green, and blue light that come from each sensor, and store it to a file. You could then add another digital-to-analog device that could read that file, and turn on and off the lightbulbs on the board to replicate the picture from the \"recording\". Add years of technology advancements, miniaturization, and replace the board of lightbulbs with small LCD/LED displays, and you have the modern camera.", "I found it easier to understand although not as detailed this way: we have found semiconductors that change electrical values according to the amount of light that hits it. We make this sensors in tiny little sizes, so we fit millions (each megapixel is a million pixels) of them on a small square. Then we make lenses to focus the light into the array of sensors and we measure the change on every one of these. Now these values can be stored and translated to different formats and things.", "Before we get to the whole image let's consider a single photon and the detector. The detector is literally a grid of electron buckets. Each electron bucket corresponds to a single pixel in an image. Over the electron buckets is a sheet of a highly engineered material alloy (silicon for visible spectrum cameras). The object your imaging generates a photon which travels to the camera, through the lens (which directs the incoming photon to the detector) and then strikes the detector. Now when a photon hits the silicon sheet it can either be absorbed or reflected. If reflected, off it goes into the void of the detector housing and hopefully doesn't come back to the detector. If absorbed, the photon raises the energy level of the atom in the silicon sheet it struck. But this new energy level is unstable and so it emits an electron. That electron travels through the silicon and gets caught in the nearest bucket. Repeat this process a few million times over each bucket in the silicon and some of the buckets will be really full (cause there were a lot of photons coming from some object), some empty (dark objects), and some in between Electrons have charge, so as the shutter is open the measured charge gets higher. When the shutter closes the cameras electronics measure the charge in each bucket and map that charge measurement to a pixel brightness value. And viola, you have an image." ], "score": [ 10, 3, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gnhar8l" ], "text": [ "The actual density is pretty low so the total energy isnt that high. The magnets are also huge." ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gnjnj8i", "gnjoe3u" ], "text": [ "Texan native here currently living up north, and still in disbelief of what's going on down there Power grids go through seasonal changes to prepare for anticipated needs well in advance, since they're anything but simple circuits- they're a complex network of of generation units all over the grid constantly balancing and sharing their load as efficiently as possible. In the summer, the grid is set up with plenty of generator capacity on standby to cover the load of heavy AC use so there aren't issues with supply. Since Texas winters are comparably mild, the power grid was not configured to carry the extra load of snowed-in Texans cranking up their heat statewide in such an unprecedented winter storm. The cumulative effect is blackouts in areas where power demand exceeds what the grid can supply.", "The heaters are using more energy than AC. There are a couple of reasons for this First off, if it's in the teens I assume people are keeping their homes at 68-70 (at least) This means there's over a 40-degree difference in temperature between the outside and inside. If you keep your home at 68-70 during the summer that would mean it's as hot as 120. The record high in Texas isn't even that high. A higher temperature difference means your heater or AC needs to do more work just to keep your house at the temperature you want. Second, AC is more efficient. AC is literally more than 100% efficient. (which sounds like it violates the conservation of energy but it doesn't) Without going into *too* much detail, all AC does is moves energy. This means it can spend 1 unit of energy to remove 2 units of energy from your house. The only way a heater can heat your house\\* is by using 1 unit of energy to add 1 unit of energy to your house. A heater can only ever be 100% efficient. \\*Technically you can use a heat pump, which is basically an AC in reverse and therefore can also be over 100% efficient but those are super rare at the moment." ], "score": [ 14, 5 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gnjt99o", "gnjvfn5" ], "text": [ "If you spin a magnet around a copper wire it will make electricity. So they use the water falling from the top of the dam to the bottom of the dam to spin the magnet which makes electricity", "An electic motor always works two ways. Either you put in electricity in one end and mechanical motion comes out the other, or you out mechanical motion in one end and get electricity out of the other. A generator is literally just an electric motor running in reverse. You just hook that shaft of that electric motor to a turbine, the water spins the turbine when it flows and et voilá, you have electricity" ], "score": [ 13, 4 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gnk8wfo", "gnk7m2d" ], "text": [ "Electric vehicles do not produce emissions directly, but the electricity that powers them has to come from somewhere. Often that somewhere is fossil fuels burned in a power plant. Those emissions are worth considering. \"Well-to-wheels\" is a way of looking at that process to better quantify what the environmental impact of driving an electric vehicle is. It looks at the emissions that were incurred from the oil well (or coal mine, etc) to getting power to the wheels of the car. When this comparison is done fairly against internal combustion (\"regular\") cars it paints an accurate picture of how electric vehicles stack up against their IC counterparts, with the caveat that electric vehicle technology allows a region to transition into greener power generation technologies at a grid level without worrying about millions of gasoline engines that would need to be replaced to lower emissions. Often, however, this \"well-to-wheels\" analysis isn't presented fairly, where electric vehicles are made to answer for all of the emissions even tangentially related to the vehicle while IC cars are judged only for the gasses flowing from their exhaust pipes. It's wise to view analysis like this critically and judge for yourself whether the analysis is fair.", "Overall emissions. Because an electric vehicle does not burn fuel itself does not necessarily mean it's zero-emissions. The energy had to come from somewhere, and for most of the world it's fossil fuels, which means the power station generates the emissions instead of the electric vehicle." ], "score": [ 10, 4 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gnli0f1", "gnli1go" ], "text": [ "They lift the cab and boom and insert a section of truss....over....and over.... and over agin URL_0", "I assume you are talking about a tower crane. You’re correct in the sense that another crane is required but the extension boom of a mobile crane can actually lift the pieces of the crane quite high. The bottom of a tower crane is bolted down to the ground and sections of the frame and slowly added and attached until the desirable height is reached." ], "score": [ 11, 4 ], "text_urls": [ [ "https://youtu.be/vx5Qt7_ECEE" ], [] ] }

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{ "a_id": [ "gnlua8w" ], "text": [ "The ship will displace water equal to its weight so a floaty box of metal that weighs 10,000 tons will displace 10,000 tons of water But \"displacement\" of a ship isn't just about the ship. The displacement is the amount of water the ship pushes away *when loaded to a specific level*. This actually turns into several different numbers depending on the era and method of measuring but things like Net Tonnage aren't actually about the mass of the ship, it's an administrative measure that goes into port duties. Deadweight tonnage is about the total mass of cargo the ship can carry Regardless, basically never will you see something that actually measures the mass of the metal of the ship. It almost always includes at least drinking water, fuel, provisions, and minimum ballast. And yeah, it's confusing" ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gnn87ls", "gnn8baj", "gnn8sev" ], "text": [ "Yes, there are differences in torque, wear, and failure modes. Slots provide a lot of torque, but can slip out and harm the product. Phillips cam out under torque, so they are less likely to slip. Torx and other fancy styles have higher torque without cam out, but they can wear more quickly. Exotic fasteners serve to make it harder for users to get inside and mess things up, the options are endless.", "Standard slip all the time and are the worse choice. Phillips are better because the cross design makes the screwdriver self-center. Robinson are the best because the square hole is so superior. Self- centering, and the square shape means you can torque the shit out of the screws without the screwdriver slipping. Robinson never really caught on outside of Canada though.", "It does not affect the strength or integrity of the screw. The advantages is purely in the price of the screws and when installing the screw. A Robertson screw have the advantage over slotted screws that it have four surfaces instead of two so it can take twice the amount of force before deforming, and it is also self centering so that the screwdriver is always in the center where you get more torque. So you can apply much more torque to a Robertson screw then to a slotted screw of the same dimension. Phillips screws on the other hand is designed to prevent overtorquing. If you apply too much force to a Phillips head the screwdriver will push out instead of deforming the head of the screw or stretching the threads. This makes it much harder to damage the screw when fastening it then with the Robertson screw. Modern screws use hex drives or torx. These are both six sided which allows you to apply even more torque then with the Robinson screw. The torx do allow you to use more force then a hex drive but is slightly more expensive to manufacture. Hex drives can also be driven at an angle with the correct tool. So if you compare screws with older style heads to the ones with the newer style heads the older styles tends to use a larger head. This is because you need the larger head to get enough torque without damaging the screw. Whereas a newer style head can withstand a lot more torque with a smaller head. But once the screw is fastened there is no difference between the different styles. Edit: Robinson - > Robertson" ], "score": [ 22, 9, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gnppdex", "gnpoxwj", "gnpp3l8", "gnppglr" ], "text": [ "Two big things to start off: there are two major classifications of power lines Transmission and Residential, and power \"quality\" deteriorates the further you are from a substation. The transmission grid operates at very high voltage and typically is far removed from people. If you've ever seen very large towers with trees cut back about 50m, those are transmission lines. They connect your generation to various substations around the country. The substations are essential giant transformer hubs. The substations usually step down the voltage to lower levels and act as the starting point of the residential system. These substations have individual lines that spread out to provide power to most residential and small commercial customers. Most of the residential electrical grids are designed to facilitate small transfers, i.e. moving a few hundred customers from one line to another. This allows your local electric utility to minimize impacted customers during an outage, but it requires the other line to be operational. Usually your electric utility is aware of which transfers they can make and which they can't, but they'll never be able to transfer a complete from one substation to another just because the breakers at the station can't handle that demand. Essentially, each line has a maximum amount of power it can provide, and utilities typically try keep that amount just above normal demand in order to make money. The reason Texas can't provide power through the existing grid is simply that it's not designed to provide power in any direction. The design is based on power being generated at specific locations and relayed out in a set manner. In fact, protective devices are places on the lines to prevent the grid from operating in any other configuration. This means that even if power were available from somewhere else, it would need to be fed into the grid at specific locations in order for the grid to work, and there is no connection available to inject power at those locations. & #x200B; TL;DR: The power grid is somewhat directional.", "The electric grid is old and built with the minimum funds to get it mostly functioning. You wouldent buy flood insurance for a house 100 miles inland. They didn't make it winter weather resistant.", "The connected grids have no surplus power to sell to Texas. They're having their own shortages.", "There are agreements in place and not unlimited excess capacity outside the local grid. So if the scale of the issue is too large, the grid operators will \"disconnect\" the grid so that the problem in one area doesn't spread to other areas too. This is essentially what brown outs are at the more local level. Rather than risking an area wide and unpredictable outage, the utilities do a planned outage - trying to mitigate or localize the impact. Generating heat is a very big drain on electrical power. The bigger the temperature difference and the poorer the insulation, the worse it gets. Electrical grids can also be a bit like freeways, they are designed to handle some traffic but they will gridlock if EVERYONE decided to travel at the same time. This kind of unusual weather might mean poorly insulated houses which aren't a major problem generally become huge issues when people try to keep warm. Since Texas doesn't normally deal with this issue, it is likely that there just isn't enough spare capacity available (unlike in states that deal with very cold weather very regularly)" ], "score": [ 30, 7, 6, 3 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gnqdhb3" ], "text": [ "A regular DC electric motor relies on a device called a \"commutator\" to allow the regular switches in magnetic field that allow it to spin. This is basically a pair of metal contacts mounted on the motor shaft. Current is transferred across to these contacts via stationary \"brushes\", which might be metallic or carbon. A brushless design, on the other hand, uses electronics rather than mechanical means to switch the magnetic field. This means they don't need the commutator or the brushes, and more importantly, means they last a lot longer because brushes wear out over time due to the constant rubbing between them and the commutator. It also makes their speed a lot easier to control. This is why PC fans have been using brushless motors for years." ], "score": [ 6 ], "text_urls": [ [] ] }

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{ "a_id": [ "gnrgjtm", "gnriemp", "gnrp08b", "gnrsru7", "gnrilzq", "gns10hc", "gnrg4l2", "gnrrzil", "gnroqgi" ], "text": [ "The biggest issue has been with natural gas and coal plants shutting down due to equipment malfunctioning from the cold. It wasn't built for extended temperatures THIS cold. The infrastructure was built to withstand the sweltering heat and produce enough electricity to run all the AC. Electricity is produced on a just in time method. If there is a sudden spike in demand, then the plants have to ramp up production in real time. At the same time that power plants started ramping up for demand, they stalled and stopped producing. Demand continued to grow and they couldn't produce enough. The grid can pull from other close regions, but if all the regions have the same issue then you are stuck without power. That's all of Texas for a second day.", "Cause #1: Heating increased demand for natural gas beyond design capacity. Cause #2: Natural gas well heads and infrastructure froze due to lack of winterization causing drop in supply - > electricity generator shutdown Cause #3: Gas supply shortage causes massive spike in spot prices on the open market, impacts ability to economically meet rates (i.e. cost to produce much higher than price to sell) Cause #4: Majority of TX grid is independent due to decision to operate outside of federal regulations, this limits ability to get electricity from neighbors and allowed infrastructure standards below federal levels (e.g. not even Basic winter preparedness both for gas and renewable infrastructure - both are working fine in northern states) Cause #5: we entered a feedback loop whereby people trying to stay warm chased and overloaded available fuel sources for heat generation causing cascading failure in the overall energy supply system Irony #1: wind has actually produced more electricity during this event than it typically does during February. Irony #2: By isolating itself to eliminate federal regulations, TX effectively reduced it's grid reliability and recoverability. While this saved operators a money (a small portion of which was passed on to consumers), it's the consumers who are likely to beat a majority of the cost from the resultant damage (both damage to their personal property and repair costs for damaged energy infrastructure). If you care to, see how El Paso fared, which is not participating in the texas grid vs well almost all the rest of texas. It's a great showcase that while market driven core infrastructure is in my opinion beneficial, market driven infrastructure without (consumer protecting) regulation is a house of cards and in all cases the consumers are the ones who pay for the price of its failure while it's operators continue to take profits.", "They are not experiencing a problem with demand. The problem is the energy companies never bothered to winterize any of their utilities. They wanted to blame wind turbines freezing (yeah like the biggest oil procing state uses mostly wind), but that AND natural gas pipes that fed the power plants froze over. Just nothing there was meant to be used in sustained cold.", "I work in the petroleum industry in Norway. During design of the electrical utilities we have to factor in winterization of the process systems, which means that a lot needs to be heat traced and insulated. Depending on the process you might get slush or hydrates if the temperature gets too low, which in turn can plug pipes and whatnot. Also, much of the gas needs to be \"dried\" which in turn is done through large heaters - and I am guessing the texan ones are not especially winterized. Edit: Electrical engineer so I do very little in the process systems, just make sure they are kept within temperature specs.", "In addition to other correct answers, the reason why the demand is so high is that Texas homes are not designed to have high efficiency heat systems. Rather than a gas furnace for example, they will have a heat pump and optionally heat strips; both of which are not very efficient when it comes to very cold temperatures. As a result, these units are on almost all the time to keep up and some never do. So the power demand is much higher than the system was designed for.", "So many wrong answers here... Texas didn't like the rules the rest of the country laid out for generating power so they picked their ball up and went home, they also closed their property to the rest of the country. If they had followed the rules that the majority of the rest of the country followed for generating power two things would have happened: 1. They wouldn't have lost their power generation in the first place- it's a supply issue, not demand issue. 2. Their friends could help out with any emergency power shortfalls by sending them power (they can't because Texas closed their property to them).", "Not an expert, but a tweet I read pointed out that the usual temperature difference (inside/outside) is about 30 degrees (100-70) while the current difference is more like 60 (70-10). Also the houses are built to shed heat, not hold it in.", "Natural gas has moisture in it, during freezing temperatures natural gas piping can freeze if not winterized. Texas gets a huge amount of power from gas and none of it is winterized meaning supply shortages and blackouts.", "When the AC runs, what’s the typical temperature difference between outside and comfort inside? 30 degrees? When it’s this cold, what’s the difference between outside temp and comfort inside? 60 degrees? Are Texas homes built to retain heat or expel heat? And then there is the issue with the power grid itself, disconnected from surrounding states (only state like that in lower 48), and a deregulated power industry that wasn’t forced to take precautions other power companies take because they’re not under Federal jurisdiction because they opted out of national power grid." ], "score": [ 519, 97, 45, 23, 12, 12, 4, 3, 3 ], "text_urls": [ [], [], [], [], [], [], [], [], [] ] }

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{ "a_id": [ "gnrmbz3", "gnrrfm2", "gns15kp" ], "text": [ "They force the car to say in lower gears rather than shifting up automatically as you accelerate. It's a carry over from the days of manual transmissions where you had the control of remaining in a lower gear for certain situations, like towing or hilly roads. They added that option to automatics as well, but most transmissions/brakes are now so effective/efficient there's less reason to ever use that feature. It's also for 16 year olds driving their mom's subaru so they can pretend to shift like they're in fast and furious.", "They limit the vehicle to the lower gears, which can be useful in some situations where you have high loads or weird road conditions. On a modern vehicle, they're largely unnecessary as the ECU and transmission systems are smart enough to handle traction control and optimal shifting. *However,* they still have one very useful function; engine braking. By forcing the car to stay in a low gear and cutting fuel flow to the engine, your engine turns from an energy source into an energy sink (it's basically just an overengineered air compressor at that point), which can be useful for slowing the car down without having to use the brake pads. This is particularly useful for very long driving segments down mountains.", "Lower gears slow down your car without wearing out or heating the brakes. This can be important when rolling downhill for a long time, especially when crossing a mountain range. If you keep in your regular gears and use the brakes all the time, they might overheat and give out, and then you're on a downhill slopw with no way of stopping. In my country, downhill highways occasionally have [gravel pits]( URL_0 ) in case someone screws up in that regard." ], "score": [ 25, 21, 4 ], "text_urls": [ [], [], [ "https://de.wikipedia.org/wiki/Notfallspur_(Gef%C3%A4lle)#/media/Datei:A7-Notbremsweg.jpg" ] ] }

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{ "a_id": [ "gnskhbs", "gnsk7ie", "gnskjhl" ], "text": [ "Flatheads are trivally easy to machine, and Phillips heads have their own issues, namely that they strip easily.", "Flathead allows higher torque than phillips. Phillips are designed to cam out at high torque. And flatheads are cheaper to produce than phillips", "This has been reposted a few times recently, but first of all, the term you're looking for is screw*drive.* The head part refers to the shape of the top of the screw, you can have a flathead phillips drive screw. Long story short, there are benefits and liabilities to all the different drives. For example Flatdrive screws are hard to pick up with a machine, easy to drive using ad hoc tools like a butter knife, prone to slipping and damaging the surface of the material, don't stick easily to drivers. Phillips drive screws are easier to pick up with a machine, strip easily with excess force, stick to drivers, not easy to improvise a driver. There are tons of other specific drivers that are uniquely more secure (require specialized tools to remove), allow for increased torque, easier to repair, etc." ], "score": [ 5, 4, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "gnswdju" ], "text": [ "All the words aside, the question is fairly basic. Do the regulators prefer a, more or less, permanent x% increase in power price or suffer y% downtime? From an engineering standpoint y can be lowered at exponentially higher increases in x. At some point, there is an acceptability cutoff. It isn't a question of who is better or more deserving, the user bears the end cost." ], "score": [ 3 ], "text_urls": [ [] ] }

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{ "a_id": [ "gntb6ti" ], "text": [ "Short answer, they actually can be if they are heated too hot or for too long Long answer, solder used to create the connections has a lower melting point than silicon, gold, copper, and other components in an integrated circuit. So the solder is going to melt before any damage to the IC happens. However, this is only the case if heat remains below the limit of the IC, if it goes over or if the heat application causes the IC to heat up to that limit, the chip can be damaged." ], "score": [ 5 ], "text_urls": [ [] ] }

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{ "a_id": [ "gntnmbb", "gntnmv1", "gntoijl", "gntnull", "gntnqwm", "gntnu0y", "gntnj5i", "gnu3m1d" ], "text": [ "When water freezes it expands by almost 10%. It does so with an incredible amount of force; more than typical plumbing pipes are designed to withstand.", "Water actually expands as it freezes. The pressure of this expansion can be on the order of 30,000 pounds per square inch. Easily enough to break metal pipes.", "Pipes are not solid, they are full of water that hulks out when frozen. These days most pipes are made from easy to break PVC rather than metal. But even copper metal pipes are relatively soft and easy to break. Older iron pipes when new were tougher, but most are now very old and rusted to the point they too can break easily.", "All of the above, plus metal (like most substances) can become more brittle at lower temperatures.", "Water expands when it turns to ice. Ice is incredibly resilient. Since ice is taking up more room than the water was, it doesn’t actually take much for all that pressure to quickly rupture a pipe.", "When water turns to ice, it expands. The force with which it does so is strong enough to burst pipes open, even thick metal ones.", "Water gets inside/around and turns into ice. When water turns from a liquid into a solid it’s very hard and it expands, cracking the pipe", "As many have said in other comments. When water freezes it expands with tremendous force. This will break plumbing. As the water freezes and expands it pushes out on the fittings and walls of the pipe and will cause it to burst and split. Often you will not notice the break until the pipe thaws out. When it does you may have a small leak or a gusher. This is the primary reason a pop(soda) can explodes in the freezer. You can prevent this by doing a few things. * Drain the lines if possible during cold months * Keep water running, such as a small flow at your sinks * Heating the area around problem spots with heat tape or space heaters (much more costly) There are 3 main types of plumbing in current buildings today. They are copper pipe, CPVC pipe, and PEX pipe. They all react differently under the load of frozen water inside them. Here is a video where a builder tests the different types under freezing conditions. It is an interesting 13 minutes. URL_0" ], "score": [ 35, 17, 11, 9, 7, 6, 3, 3 ], "text_urls": [ [], [], [], [], [], [], [], [ "www.youtube.com/watch?v=OOeBJ8mDr8Q" ] ] }

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{ "a_id": [ "gnvgtf9", "gnvivti", "gnvism7", "gnvhqtl", "gnvtkz6", "gnvzq02" ], "text": [ "Insulation and a smart/prepared layout help A LOT. For example putting a waterpipe right next to the heating water pipe prevents both from freezing while heating is in use.", "It is not uncommon to run water pipes outside the insulation if you do not expect any freezing issues. This is both as an easy way around beams and also makes the water pipes easy to install, inspect and maintain.", "When water freeze, it takes more space than it did as water. As a result pipes freezing is a big issue. But the world is vast. Different places face different problem. Countries that face freezing temperature regularly will put much better insulation in their infrastructure. They'll also use stronger pipes to avoid burst and make regular maintenance when they detect any issues. Place that do NOT face freeze in a regular basis don't put these. Why would they pay an extra cost for an issue that should not happen? It's much more likely that Texan pipes are made to handle HIGH temperature, preventing dilatation from tempering with the pipes. In hot places, you prepare pipe for heat. In cold places, you prepare pipes for cold. Texas is more used to heat than cold.", "If you have no heat then the pipes freeze. Same would happen in northern climates if they lost heat.", "First off, it wasn't \"barely freezing\". I live in San Antonio and the cold started Sunday evening. It was 10F (-12C) Monday morning, 14F (-10C) Tuesday and did not go back above the freezing point until Wednesday morning. That's a long cold snap for this area. Pipes are buried fairly shallowly here due to a layer of limestone near the surface and are not insulated. We dripped our outside hose faucets and did not have any burst pipes although we saw several while driving around the local area.", "Climates that are used to those kind of temperatures are better equipped to handle it. Imagine if you lived in Russia. Would you have the same wardrobe as someone in Jamaica? Likely not! Likewise a house in Texas will be built for very different conditions than one in Canada. When a country is always getting certain temperatures, it will naturally make its buildings and services to not break under those temperatures. If it suddenly gets temperatures that are well outside of normal, they aren't as well prepared and things start to break. If your buildings never needed mega insulation and double paned glass before you're probably not gonna have that available during a rare shift in weather. Heck, a lot of Texans had never even seen snow before!" ], "score": [ 9, 5, 5, 4, 4, 3 ], "text_urls": [ [], [], [], [], [], [] ] }

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{ "a_id": [ "gnwn2dl", "gnwux2b", "gnwovb2", "gnwpfbf" ], "text": [ "The federal government passed some laws saying that it had the power to make states play nice together and share power if one state ever had an emergency situation like this. Texas was like \"We're proud Texans, gotta do our own thing, stick it to the man - can't make us do share something if we can't technically share it!\" and so they went off and made their own power network.", "They refused to be part of the national grid to avoid federal regulations and requirements, like winterizing the grid to prevent this sort of break-down. Money. It really is that simple.", "It seemed like a good idea at the time. As T. Boone Pickens said, \"In the history of America, we've never had an energy plan. We don't even realize the resources we have available to us. Texas is the Saudi Arabia of wind energy in the world, on top of being the Saudi Arabia of oil in the US.\" Power consumption is Texas was engineered as a summer air conditioning problem. There are peak load plants, powered by natural gas, to handle the hottest days. Alas, these plants aren't winterized, because it made them cheaper to build, because winter is the \"low electricity demand\" time of year. Then an ice storm downs a bunch of wires and people need gas to heat their houses and the windmills are all frozen (because winterizing them also would have cost more) and the next thing you know, you've engineered in a failure mode.", "The Federal government has the power to regulate power grids that cross state borders as a direct result of the Commerce Clause. Texas didn't want that, and so they ended up with a grid that's entirely internal to Texas, in order to ensure that the Feds couldn't regulate them. This is entirely in keeping with the idea of Federalism, but it also means that Texas is more exposed to systemic risks because they can't lean on the rest of the US power grid for help like everyone else can." ], "score": [ 46, 19, 15, 8 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gnwy6cy" ], "text": [ "What you’re seeing is called walking induced vibration. This is called a “serviceability” issue rather than a “strength” issue - ie the building is going to stand up just fine, but the performance may not meet the expectations of the occupants. This is often an issue with steel framed floors, sometimes an issue with concrete framed buildings. Walking induced vibration is affected by several factors: 1. Beam span. Less is better. 2. Beam spacing. 3. Beam and floor stiffness. Stiffer is better. 4. “Length” of floor that can vibrate. Longer is better. 5. “Width” of floor that can vibrate. Wider is better. 6. Weight of floor. More is usually better. 7. Damping. More is better. Mezzanines suffer on items 4, 5, 6 and 7. The “length” is the length of floor in the direction of the beams. It can extend into the next column bay if the beams there are in the same direction as line up with the mezzanine beams. They often aren’t. So instead of three column bays (columns are often laid out in a square grid, each square is a column bay, if you try to vibrate the floor in a column bay it’ll shed some into the adjacent bays) length you only have one contributing to reducing vibration. The width can include the adjacent bays in the opposite direction to the length. On regular floor bays this can be 3 or more column bays. On a mezzanine it might only be 1/3 of a single bay. The reduced width makes it more susceptible to floor vibrations. The weight includes all the stuff that’s always on the floor. In regular column bays there are partition walls, desks, etc. mezzanines are usually clear so have less mass. This makes them more susceptible to vibrations. Damping - this is the ability of the floor to shed energy from vibrations. Things like partitions between rooms help this substantially as they absorb energy from the floor trying to vibrate, but mezzanines rarely have any - they’re a minimally damped part of the structure so floor vibrations can build up much more easily. Mezzanines are also often hurt by beam span too - they’re often a longer than usual span, for a nice column free area in the open space below, but the long spans put the natural frequency close to walking speeds, which makes floor vibrations more problematic." ], "score": [ 4 ], "text_urls": [ [] ] }

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{ "a_id": [ "gnxoo0d", "gnxmg7s", "gnxqzhh", "gnxo8jk", "gnxmx0y", "gnxs9ia" ], "text": [ "Under normal atmospheric conditions, water expands to 1700 times it's volume of steam meaning it is a very good way to convert thermal energy to mechanical energy to turn a turbine.", "There really isn't a better way. Electricity is typically made by spinning a magnetic field inside a coil of electrical wire. No matter what the fuel source, you only make power if you can turn the magnetic field. Using steam is the best way to do this - as long as you can make heat, you can use that heat to boil water and the steam to turn a turbine. There are some methods that don't use water - some solar panels just make electricity directly and wind turbines use wind rather than steam - but for most other fuel sources still use steam.", "There are other ways. Gas turbines are basically jet engines sitting on the ground; they're fuel hogs. Supercritical CO2 turbines may be better than steam, but they're still in the R & D stage.", "Solar panels aka photovoltaics create electricity through photochemical effects on silicium-layers other than solar thermal energy which just heats water or oil through heat absorption. When building Power plants with nuclear reactors inside one thing you'll always need is water to keep your buildings cool and safe. By cooling your reactors the water gets hot and creates pressure, so turbines actually are the most effecient choice to convert energy.", "Photovoltaic also go directly from sunlight to electricity. To the question, it is very easy and efficient to heat water to produce pressurised steam and use the steam to turn a turbine. Using the fuel in an engine to turn the rotor of a generator would lead to a lot of power loss and (probably) more maintenance too. \"Most\" electricity power plant can also run at the same power output for long period of time so they don't need to \"speed up or down\" much like an engine would be capable of.", "There are two other ways: the thermoelectric effect and Stirling engines Thermoelectric effect Advantages: zero moving parts, can still work if the maximum temperature is under 100 Celsius Disadvantage: inefficient as all hell, low power Stirling engine Advantages: can still work if the maximum temperature is under 100 Celsius Disadvantage: low power These don't usually find their way into power plants, but they have their uses on space probes, lighthouses, server farms etc" ], "score": [ 21, 19, 5, 4, 4, 3 ], "text_urls": [ [], [], [], [], [], [] ] }

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{ "a_id": [ "gnydhi7", "gnz2jtw", "gnzalny" ], "text": [ "Operators shut down switching equipment that was very close to overloading. Well, \"seconds\" may have been hyperbolic, but this equipment is extremely specialized and there are not huge stockpiles of unused equipment waiting for someone to want it. Losing too much switching equipment might lead to months of rolling blackouts as replacement equipment was manufactured. Most world power grids are susceptible to this sort of thing, nobody has a spare power grid to use for fallback. A large solar storm or coronal mass ejection could fry enough transformers that it would take months for worldwide power to return to normal.", "An electric grid is a balance of push and pull. Most grids right now have little or no storage, which means the grid has to maintain enough flow to feed the demand without exceeding the maximum amount the grid can handle. Because it is a network there is some capacity to buffer by opening and closing distribution nodes and varying the amount of production coming from power plants. You want to do this within a fairly short period of changes to demand-- seconds to minutes, no more. If you have a smaller network like Texas that normally has some number of plants running (let's say ten for the sake of discussion) and one of those plants stops its production, in this case valves and other machinery that moved the gas (which drove the plant's generators) iced up. Now the grid is operating at 90% output. Once this happens, either a percentage of the remaining nine need to pick up the slack by increasing their output, or... you shut down a percentage of the grid equivalent to that plant's output. Either up the output or decrease the demand. Long story short, this sequence of balancing can set off a cascade of ups and downs that ripple through the network as the system tries to maintain the narrow window of balance mentioned up top. If two plants still online try to compensate for the decrease of the plant that went down and overshoot, then cut back and drop under. Then plant five may ice up and things get more complicated. The push and pull becomes the equivalent of a truck that starts fishtailing-- the more the driver struggles to correct things, the bigger the oscillations grow. At some point this push and pull results in a power dump so big that you are in danger of overloading some major piece of equipment, and you have to cut off production entirely and start turning things back on one-by-one. It must be stated that these type of situations are actually somewhat common, but MOST of the time the electricity can be shunted around the network enough to allow the operators to get the situation under control without cutting anyone off. There are exceptions, some very notable, but those are unusual. The other possibility is that so much production went down that the remaining plants tried to take up the demand and ended up overloading their capacity, which would also fry equipment. & #x200B; Either way, once the problem moves from the category of \"evolving, use the network's buffer volume now to correct\" to \"overload imminent, you're f'd\" the only good option is to literally throw the switch and completely knock out the whole thing in order to prevent equipment loss. Then you can start turning things back on in a controlled fashion, though in this case the gas lines feeding the power plants are iced up and can't get the gas they need to turn their turbines, so there is no turning on that can be done. & #x200B; [ URL_1 ]( URL_0 )", "From the [Houston Chronicle]( URL_1 ): > \"As natural gas fired plants, utility scale wind power and coal plants [tripped offline due to the extreme cold brought]( URL_0 ) by the winter storm, the amount of power supplied to the grid to be distributed across the state fell rapidly. At the same time, demand was increasing as consumers and businesses turned up the heat and stayed inside to avoid the weather. > > ... > > The worst case scenario: Demand for power outstrips the supply of power generation available on the grid, causing equipment to catch fire, substations to blow and power lines to go down. > > If the grid had gone totally offline, the physical damage to power infrastructure from overwhelming the grid could have taken months to repair, said Bernadette Johnson, senior vice president of power and renewables at Enverus, an oil and gas software and information company headquartered in Austin." ], "score": [ 486, 75, 18 ], "text_urls": [ [], [ "https://en.wikipedia.org/wiki/Cascading_failure", "https://en.wikipedia.org/wiki/Cascading\\_failure" ], [ "https://www.texastribune.org/2021/02/16/natural-gas-power-storm/", "https://www.texastribune.org/2021/02/18/texas-power-outages-ercot/" ] ] }

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{ "a_id": [ "gnzjybl" ], "text": [ "Redline has nothing to do with power output. The engine spins easier without having to be burdened by the drag of the transmission. You can reach your maximum speed on a bicycle easier while carrying nothing quicker than you can while carrying something on the bicycle with you." ], "score": [ 8 ], "text_urls": [ [] ] }

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{ "a_id": [ "gnzplfq" ], "text": [ "Metal is a crystal structure. All the atoms line up in neat little rows. But these rows aren’t perfect, especially where two “crystals” meet. When you bend and unbend the metal, these tiny tiny little flaws in the crystal end up grouping together. The more bending you do, the bigger these “voids” end up being. As this happens, the metal in the area gets harder but more brittle. It can’t bend as easily because of the voids getting in the way of all the. Structure moving. Eventually it gets so stiff and so weak that it just snaps. Just bending it back straight does not fix metal fatigue. The only real way to get the fatigue gone, forever, is heat it back up to where the atoms can move freely and then re-cool it. (Re-smelt it). It’s all to do with the crystal lattice and how the different areas of Crystal lattice interact. [interesting paper ]( URL_0 )" ], "score": [ 14 ], "text_urls": [ [ "https://www.nde-ed.org/EducationResources/CommunityCollege/Materials/Structure/strengthening.htm" ] ] }

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{ "a_id": [ "go1wnud" ], "text": [ "First... as someone who grew up in south Flordia but now lives in Arkansas, let me just say... if Ft.Lauderdale or Miami ever needs to worry about \"winterizing\" we've screwed our climate past repair. Cash in your chips, because the game is over. So, no. They don't winterize in Southern Florida, although parts of the panhandle might have a light bit of it. Their main concern is hurricanes. That said, as much as the powers that be deserve to be taken to task for the state of the electrical system in Texas, that isn't the whole picture either. Winterizing is more than just something done by the infrastructure in the area. It is done by the population as well. As a Floridian, think of it this way: What if a hurricane came through and no one had made sure they had Non-perishable foods, flashlights, camping stoves, emergency medical supplies, sand bags, ect? What if no one secured their shutters or pulled in their yard decor? What would happen? Even *if* Ft. Lauderdale had built perfectly and all the drainage systems ran without a hitch (keep dreaming), it wouldn't matter because if the power went out, no one cloud deal with it. Part of preping for a hurricane is anticipating that you may loose power and collecting appropriate supplies to deal with that, right? Every Floridian knows that. Preping for winter weather is very similar but the supplies change. In both cases, you need flashlights, med supplies, etc. and you *need to anticipate being without power.* The difference is, in Florida, it won't be 10 degrees out. In Arkansas it will be. So, here, I need to have things like propane heaters, thick survival blankets, HotHands packs and other warming supplies. I'll also need bags of de-icer salt instead of bags of sand. Those things are vital in dealing with freezing weather during a power outage and, like Floridians, your average Texan isn't going to think about keeping them on hand because until the last 20 years, it was inconceivable to need them. Even then, it is still only needed once a decade or so. I'm dealing with the same ice-storm that hit them. I also risk loosing my power and have a ton of ice and snow outside. But unlike Texans, I have the necessary supplies in my emergency stach that they normally have no reason to keep. This compounds the issues Texas is having. Power normally goes out in ice/winter storms, just like it does in hurricanes, no matter what a city does. How you prep and deal with those outages is the issue." ], "score": [ 5 ], "text_urls": [ [] ] }

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{ "a_id": [ "go229dk", "go245wo" ], "text": [ "The pilot/co-pilot/flight engineer model is well known, well-tested, and still highly applicable. It still has to be flown (mostly for landing; takeoff is largely automated). The details of each knob or switch may be different but the larger use case is quite similar. **edit:** also, nearly all of the shuttle commanders and pilots were Air Force or Navy pilots. They already had thousands of hours of experience in that arrangement.", "They were both planes, in the broadest sense. There's a certain set of information that's relevant to flying any plane, so if the information is the same it makes sense to choose a UI layout that's known to pilots (many astronauts start out as jet pilots) already. And there's also a limited amount of layouts for \"we have to fit a hell of a lot of flip switches onto a panel\"." ], "score": [ 16, 5 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "go30j9w", "go37kfz" ], "text": [ "It could be a few things. The shower cartridge night have something wrong with it or the mixing valve could be bad. You can look up these terms on YouTube. I think I remember some videos by \"This Old House\" that covered this topic. They are pretty good at explaining like you're five.", "The cartridge in you shower limits how the temperature of the water that can come out to prevent scalding. It always mixes cold water in to some degree. Your tap can draw exclusively hot water without any cold mixed in." ], "score": [ 5, 3 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "go3rddp", "go3r4m7" ], "text": [ "\"Space debris\" is a continuum. The frequency of a piece of debris is directly related to the size of that debris - small particles are significantly more likely than huge chunks of matter. Satellites and space stations are just built with enough external shielding to survive the constant onslaught of tiny particles (mm scale and below). Larger objects than that are **actively tracked**, and if something is on a collision course with a space station we have enough of an advance warning to move the station out of the way using its onboard thrusters. These happen every so often, maybe once every few years. Also, there's not actually as much space debris as you might think. Space is a big, big place. Even down in low-earth orbit, the chance of getting pummeled by space debris is only really a concern for very long-lived projects like the ISS that survive in orbit for many years. And this is the \"high risk zone\". Out in the far reaches of geostationary orbit (many times the altitude), space debris is a non-issue. This is where most satellites live, especially communications satellites.", "Think about how huge the earth is at the surface. Expand that sphere several 10s to 100s of miles. We’re taking about *an insane* amount of area. It’s still a concern, but not a constant danger. When a potential impact is seen through tracking, satellites and stations can use thrusters to move out of the way" ], "score": [ 12, 10 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "go4bwva", "go4b3k7", "go4bdqp" ], "text": [ "It's like packing a room full of people, when the room is empty it's easy for people to walk in. After a certain point people keep bumping into each other and it's harder to squeeze more in.", "Think of it this way, when it's at 0% there's full of empty seat for the electricity to be in but when it reaches 80% they would have to go out their way to find those empty seats. Or a slightly disgusting analogy, after you take a dump, your first wipe would clean up most of the mess but the subsequent wipes would clean up lesser and lesser until your final wipe where its barely anything but it gets you to a 100% clean bum", "The charge flows to the positive charged plate (cathode) of the battery to be stored. The charge is positive and naturally wants to flow away from the positive charged cathode. Getting positive charge is easier to do when it is empty. Once the charger reaches ~80% the positive charge increases enough to push back on the flow of additional charge entering. It still will fill, but at a slower and slower rate." ], "score": [ 47, 13, 12 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "go571dv", "go65lxw" ], "text": [ "A battery's voltage changes with its charge. A 12v car battery might go as low as 10 volts when dead or as high as 14 when topped off. By measuring the voltage and knowing the battery type, the battery's charge can be estimated. This is, however, imperfect and especially as the device ages it becomes inaccurate.", "There are 2 methods to calculate the remaining power in a battery, and they're both kinda inexact. One is measuring the voltage of the cell(s) and approximating or looking up on a table how that voltage corresponds with a given amount of energy remaining, but it's also dependent on many things like the temperature, and how fast you are drawing current. The battery cell is undergoing a chemical reaction to make up the electrons that flow through the circuit. The chemicals can 'wear out' by degrading and breaking down to non-useful unreactive products. There can be physical damage, etc. For most people, however, this estimate is close enough. Eg. An alkaline 1.5v AA battery starts at around 1.55v, and is completely depleted at 0.8v. You can then take a measurement and cross multiply to know how much of that 0.75v envelope is remaining. Another method is to (approximately) count the electrons that the battery has produced, and again knowing the characteristics of the battery, you can say how many are remaining. Applications like electric cars and quadcopters use this, where by monitoring the current consumption as well as the voltage, they can ascertain how much charge is left. A 1000mAh battery measured drawing 1000mA for 0.5 hours has about half left. Some drone pilots display their consumed mAh in the headset so they know not just to watch the voltage count down, but also 'this 1000mAh battery has been depleted of 900mAh, best come in to land', regardless of the voltage remaining." ], "score": [ 69, 21 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "go5fcca", "go5ddx7" ], "text": [ "Jet engines are built to eat a good sized bird and fail safely, they don't have to keep working but they have to shutdown safely, the expectation is that the other engine will be enough to get the plane to a safe runway which is generally the case. Double bird strikes are pretty rare as long as you don't fly through a flock of geese, they show up on radar and are avoidable. Any grate in front of the engine would be heavy ($$$), restrict airflow hurting engine performance ($$$), and could potentially make the bird strike worse if the bird takes a piece of the metal into the engine leading to a catastrophic failure of the engine. Jet planes going down due to bird strikes is pretty rare, they lose an engine from time to time and airports have methods in place to keep the birds out of the area, but for the most part bird strikes aren't damaging enough to justify expensive additions that make every plane more costly to run all the time.", "I would assume that it would either then eat the mesh or the grate would prevent enough air to properly work" ], "score": [ 7, 4 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "go6dv7m", "go6e5l7", "go6exsv" ], "text": [ "Helicopters are powered by a big engine which moves at a fixed speed. They change their blade angle to go up and down or roll. Drones use electric motors, which can easily change speeds quickly, and so they can use multiple rotors and change speeds rather than adjusting blade angle.", "Helicopters are powered by turbines (or sometimes piston engines)...either way you need a very complex, expensive, and (relatively) heavy transmission to get that down to rotor speed and you want as few of those (and as few engines) as possible. That drives you to one, maybe two, rotors. To get the required maneuverability, you put in a ludicrously complex hub & hinge system to allow you to adjust the angle of each blade in real time as it travels around the circle. Drones are powered by small direct-drive electric motors fed by batteries. These are really easy to directly connect to the prop...no heavy transmission. The battery is the heavy part, so you have minimal batteries but you can have four (or six or eight) motors & props with relatively little penalty. Now you can control the vehicle just by altering the speed of different props...no messy hub & hinge setup required. The obvious question, then, is why not build helicopters like drones. And that's where we're headed but, right now, we can't anywhere close to even medium helicopter power from a battery. It's the same reason that the only electric airplanes are really small ones...the power plants aren't there yet. But it's not a coincidence that the raft of electric \"air taxis' in development all look like big drones, not small helicopters.", "They don't helicopters have 2. One is pointing sideways and offsets the torque from the main rotor. Drones/quadcopters have 4 that are 2 sets of contra rotating propellers, they speed up or slow down to adjust position." ], "score": [ 16, 8, 5 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "go7v362", "go7v5zp" ], "text": [ "Former automotive engineer. It's programmed into the speedometer to show that you're going faster than what you are, and increases slowly as you increase your speed. We had it set so that when you were showing that you were doing 70, you were actually doing 65.", "It will be a percentage. If it stayed at 3mph then when you stop it would still read 3mph, but that doesn't happen. At 0 mph your speedometer is 100% accurate. As you increase speed it will deviate more and more. Use a GPS speedometer app on your phone and check how far off it is at 50 mph. Speedometers by law are allowed to be a little off, as long as they read a little fast just like yours. If it is way off you can have it adjusted." ], "score": [ 7, 5 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "go8donu", "go8dhgy", "go9ayh9", "go96ybi", "go8ired", "go9b5fe", "go9ibvi", "go8lv3q", "go9d6uo", "go9fx0g", "go9g0xe", "go9ct3p", "go9iiue", "goaa94h", "go9rme7", "go9co4n", "goa4g5d", "go9bao9", "go9ph4a", "go9l27o", "gob8g2r", "gobfbeu", "goa9zlg" ], "text": [ "Roads have a slope limit, called the road's grade. If the road is too steep, it will be unsafe. Mountains are natural features, and they are often more steep than this. So, to go over a mountain, you have to make a very long road to maintain the grade limit. You can do this on the mountain, with a series of switchbacks. Unfortunately, switchbacks are also dangerous and significantly increase travel time. This longer road is also much more expensive. At some point, the economics of tunneling through the mountain are cheaper than the long road in terms of construction costs plus all the time/fuel used to traverse the road. Engineers usually build the cheapest solution, even when it's a tunnel through a mountain.", "Because then highways would be like rollercoasters and be super dangerous to drive on, and impassable by larger heavy trucks. Imagine you're going 65MPH on the highway then suddenly there's a hill going up at 30º", "Weather and ice conditions will also play a role. Even if the hill isn't too steep it can be an unnecessary slope in an area with terrible winter driving conditions. The hill can be moved, an idiot cannot be taught how to drive on ice. Ft. Worth taught us that recently", "They used to. It faster and better driving to blast through hills, though it costs more, obviously. Often there will be 2 routes, the old hilly route, and the new tunnel. No one takes the old route.", "This is both an engineering and an economics question. Good answers here on the engineering reasons. The economic answer is that tunnels probably cost more to build, but reducing auto accidents and saving driving time have more economic value over the life of the tunnel.", "Come to California, where because of earthquakes we build over mountains instead of through them. Everything takes longer and the roads are shittier and more difficult to drive.", "Lots of good and right answers here. I'll just add that if an engineer can achieve something equally with an explosion or using other means, he will choose the explosion. Just sayin' EDIT: OK OK... I'll be honest... explosions will be used when possible. Its just so cool!", "I have a fun colloquial fact (never found any actual data on this) People have been building roads for millennia, check out the Egyptians and the Romans. I was told that before we knew these hard science engineering type math numbers for road grade. It was just a matter of trusting the animals the pulled wagons and carried loads. So by allowing the animal it's choice on where to walk while pointing in the right direction it would instinctually walk what we now accept is a safe road grade %. In a situation where you ran into mountains you then understand why we have many many miles of winding twisting roads trying to get over that mountain while respecting that natural road grade limit. If you want to save miles and miles of winding roads up and over and back down guess what you do? Build a tunnel or just blast a valley through the mountains. Of course this level of risk in engineering is something that modern humans mastered much better than our ancient counterparts but I bet there's some cool story out there of a brilliant commander who tunneled through a mountain pass to surprise an enemy force!", "Great easy-to-understand treatment about road design in general: URL_0 He addresses your specific question beginning at about 7:55.", "The composition of the landscape is also a factor. It's a lot easier to blast through loose earth and hills than it is solid granite or sedimentary layers like shale that won't be structurally sound even after reinforcement. Spent my childhood in Colorado and western South Dakota. You'd be AMAZED at the number of crazy roadways when a \"simple\" tunnel would suffice.", "Its cheeper to blast hill tops for back fill. You need both cut and fill to prep for a road so they are able to use the environment around the road to make a better road.", "It comes down to the fact that if you don't blast through hills, your roads have to either go up and down a lot, have a lot of curves, or both. The more curves you have and the more you have to go up and down, the slower you have to drive. A lot of curves and up's and down's also means that the road is longer than if it goes in a practically straight line, so even if you could drive at the same speed, it would still take longer. Another Problem if the road goes up and down a lot is that it's a lot harder on the cars and trucks driving over them. Think of when you're on a bicycle. What wears you out more, the straight, flat bike bath, or the one that goes up and down and has a lot of curves? Well, the same applies to the cars and trucks.", "My ex boyfriend in NZ used to bitch and moan all the time about how the roads there snake around mountains when places like Switzerland get all those neat tunnels going straight through, it's just cheaper though", "Go drive across Costa Rica sometime. You'll know exactly why. You might want to bring some Dramamine.", "Many roads are built to be \"more level\" to save fuel and meet modern fuel economy standards. Or so I once heard. Railroads in my area are so much more level than the roads next to them. Hilarious to see actually.", "Dynamite is cheap and the underground road will require less maintenance compared to something up a mountain that will get pounded by all kinds of weather.", "Confucius (might have) said, A house is only as strong as its foundation; A wise man builds their house on a slab of rock, rather than stilts", "ELI5 version: it costs less money to dig a hole through the mountain, then to build a road going all the way around it. Everyone likes to save money 👍", "Explain like you're five? Obviously because it's cheaper.", "Too steep. My dad had to excavate the entire tip off of a hill because cars would stall trying to climb it. Had to rebuild the entire highway after he cut the hill down", "I like to think about it this way. Yes, it takes some effort to shave the cap off the top of a hill so the road can be lower and straighter. But just think how much gas it saves in the long run for ALL the cars that will ever pass through there not to have to waste the energy of climbing up the hill only to come immediately back down on the other side.", "I see a lot of good answers in the comments, but I need to add one thing. If the roads/railways generally sit higher up, meaning ”cutting” less through the landscape with hills etc, the noise pollution would be way worse. Imagine heavy traffic going over a hill on an otherwise relatively plain landscape, the noise of the traffic would reach very far and affect the people living nearby a LOT more than if the road went through the hill.", "I actually work for a company that build roads in mountainous region. Besides economics, there are few other reasons 1. Weather - there are mountains where it snows all year round. It becomes unmanageable in winters and these kind of roads are usually closed for 5-6 months during the winter. 2. Safety - some hilly roads are prone to mudslides and avalanches. 3. Time - roads in mountains take a lot of time to traverse, if the road is an important connection between two points, usually a tunnel can decrease the time by hours." ], "score": [ 12104, 1591, 422, 196, 171, 72, 57, 55, 34, 22, 15, 11, 9, 7, 6, 5, 4, 4, 3, 3, 3, 3, 3 ], "text_urls": [ [], [], [], [], [], [], [], [], [ "https://youtu.be/9XIjqdk69O4" ], [], [], [], [], [], [], [], [], [], [], [], [], [], [] ] }

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{ "a_id": [ "go95mzu", "go95pn8", "go968i9", "go98cub", "go99n5h" ], "text": [ "Insulation is the big difference. In cold climates, people uses a lot of insulation to keep the cold out, same pipes, but protected from freezing due to insulation.", "Texas rarely sets temperatures this cold, and as such, pipes in many parts of the city and in many homes weren't insulated to the extent where they could handle largely stationary water at such temperatures for multiple days", "When water freezes it expands. This expansion cannot be realistically constrained by anything other than very heavy duty highly specialized equipment. In water pipes it causes them to crack and burst - the steel is nowhere near strong enough to stop the expansion. The pipes are freezing because they’re not insulated, so can freeze more easily. They’re also in buildings that have completely lost heating so are able to freeze while inside - normally this is only an issue for things like vacation homes or if you’re going to be away for a prolonged period in winter - and then you drain the pipes and turn the heat off. No water = no bursting. But it’s difficult to drain pipes in a property you’re occupying as then you lose your water supply and can’t flush the toilet, and even then - it’s not something that’s usually a risk in climates like Texas.", "I'd say it's different codes for different regions...our houses in Texas are built to keep heat out, not in", "Even the most expensive pipes can't deal with the water freezing. They will burst, unpredictably and probably at many different locations at the same time. There is also that thing, of course, where frozen water is...you know...not really in the best interest of the service provider. You can't sell frozen water to your customers, since it's not going to move anywhere. It's a pretty poor business model, to not be frost-protected. That said, It all boils down to statistics. Where I live, it's codified that water pipes must be below 6 feet (further down, if the top layer is pavement) to prevent the frost to reach down to them. It *rarely* reaches down that far, which is why that is the requirement. And I assume that is what happened in Texas too. Their standard has been questioned by nature, and now they have to pay the price for that. It will happen again, in three generations or something like that, and no-one now living will be in the active workforce then; the memories of this one freak spike in the statistics will be long forgotten once everyone agrees that it obviously doesn't happen particular often..." ], "score": [ 41, 10, 9, 3, 3 ], "text_urls": [ [], [], [], [], [] ] }

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{ "a_id": [ "go9dcrl", "go9e7yz", "go9ezn9", "go9e8lw", "go9mf7i" ], "text": [ "The blackouts in Texas were “intentional”. Meaning that the blackouts we saw were intentionally triggered by grid operators. The people that monitor and run the power grid. They did this because the grids ability to produce power was falling dramatically due to power plants failing in the cold weather. So to prevent the damage that would come from a failure blackout where the system itself actually breaks down on its own due to the intense demand and stress it’s under, they intentionally just pulled the plug. Because it’s way easier to wait for things to get better and then plug back in, then for the plug to get completely fried and have to do repairs on everything. The “seconds and minutes” quote is just saying how much time the operators thought they had before that catastrophic failure would have happened, basically saying “yes we pulled the plug and intentionally caused several days of power outages, but it was to prevent a failure that would’ve taken months of repairs”", "It's important, in a grid power system, that the generating capacity and the electrical load are balanced to one another. There's a scenario called \"cascade failure\" which is very bad. If one of the stations on a power grid fails unexpectedly and stops providing power, then all the systems that are plugged into that system are still trying to draw the same amount of current, but they're drawing it from fewer generators. This loads those generators more severely. And if they were already operating at the edge of their capacity too, then it's more likely that one of them will respond to the load spike, by failing too. And the more stations that fail, the worse the load imbalance becomes for those still online. Like I said, this situation is very bad. In the best case scenario, failsafe systems will just shut the generator down when overloading like this. But if that doesn't happen, there can be all kinds of damage to the system and it might not be safe to start up again until that damage is addressed. To avoid this situation, one of their last resorts is called 'rolling blackouts', where they simply disconnect bits and pieces of the grid to try and keep the load balanced.", "...maybe like you are 10 or 15.... Power grids require a balance between *power produced* and *power consumed* at any given moment. Power is produced \"as it is needed\" almost instantaneously. It also requires all of the generation plants to produce power at exactly the same frequency (60hz) with the power peaks (the sine wave) precisely aligned (i.e. \"synchronized\"). There are many generating plants of various sizes doing this in a coordinated fashion on a grid like that in Texas. This balance is fairly easy to maintain (waves hands...) when the power consumption is below what the power generation systems are maximally capable of producing. However, when more power is consumed than *can* be produced by the generation systems, the generation plants struggle to keep up - like a car that is climbing a hill with the accelerator to the floor - at some point, it simply can't go faster no matter how much more \"gas\" you give it - the car's engine has reached its maximum output. When generation plants reach this state of maximum power output, then they begin to slow-down (not run at 60hz any longer), and they don't necessarily degrade gracefully - some plants slow faster than others and their frequencies can become \"un-synchronized\". A grid with unsynchronized generation sources is fighting itself - instead of the generators \"pushing\" and \"pulling\" the electrons precisely in unison (i.e. being *synchronized),* they begin to \"clash\" - one generator is \"pushing\" while another is \"pulling\". The machines that produce electricity are ***massive*** \\- some of the largest machines man has ever constructed. When they begin fighting each other, very bad things can happen - explosions, fires, and general mayhem. When the grid approaches this state, the utility companies are forced to either ***shed load*** (reduce the power consumed on the grid by creating intentional blackouts), or watch the equipment (generators, turbines, transformers, etc) destroy themselves.", "Well described. Some components of the grid are custom built and/or have long lead times to procure. Think large transformers, underground cables etc. Take them out and large chunks of the grid are not coming back for months. Easier to shut them down temporarily.", "Lots of good answers here about synchronization. Another big issue is black start and I’ll talk about that. Your car battery is used to start up your car’s gasoline engine; once the car engine is running it is powered by burning gasoline. Same thing for all thermal power plants — they need a source of energy to start up initially and then they burn coal, natural gas or whatever to run. Since the grid is tied together by wires, in most cases a plant ready to startup uses electricity from the grid itself to get going. If a bunch of power plants in an area all go off-line at once, then there might be no unit left to start up the other plants, and that is a big problem. So in an emergency when a bunch of plants are tripping off-line, the grid operator starts “shedding” customers to make sure that some units keep running. This is the difference between “rolling blackouts” and “blackouts.” A blackout like this is the “months long” issue mentioned; when this happens, it takes a long time to get everything running again. Two related points: power plants usually have batteries to run critical systems, but those batteries don’t have enough energy to start up the power plant. If a true blackout happens, there are some power plants which have huge diesel engines which they can use to start up the bigger plant. Useful in an emergency but there are other issues which mean it’s better to avoid getting to the point where you need this." ], "score": [ 21, 5, 5, 3, 3 ], "text_urls": [ [], [], [], [], [] ] }

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{ "a_id": [ "goa7yke", "goa1iuw", "goa4ncs" ], "text": [ "It's a hen and egg problem. No power = no computers, valve actuators, pumps, etc. = can't start the power plant = no power. Normally, if a power plant goes down for some reason, you can rely on \"the grid\" (which are just other plants) to provide power in order get it running again. But if *everything* is down, you can't get any power, so a well-planned grid has \"black startable\" plants that can start with no external help (e.g. by having enough batteries or diesel generators on site, or by not needing much external power by design, such as hydro, where one could in principle crank open a valve by hand to start it). Once these are back up, other plants can use that power to start up themselves again. IDK what's wrong in Texas, but \"weeks to months\" to recover from a total blackout seems excessive to me. Here in Austria, operators train for having the national grid back up and running after max. 24h after an EU-wide grid failure. [source, in german]( URL_0 )", "Turns out power plants also need electricity to work. Normally they provide electricity for themselves but if they aren’t operating and they can’t tap into the electrical grid, then things get complicated when starting them up.", "A black start is another saying for a cold start. In most types of mechanical systems, all individual operations are initiated with an operation that is already functioning. In a ship for example, if you want to start the main engine, you use the air that was already pumped into the tanks. If you want pump more air into the tank to start the engine, you active the compressor which is powered by the generator. If you want to start a generator, you turn on all the parts which are operated by shore power, etc. When the starting the engine, the fuel is already warmed up by the boilers/heaters. However, if absolutely everything is shut off, then you have to go through several steps to get everything back on. The first action is activating the prime mover. The prime mover is type of mechanical device that requires the absolute bear minimum to start. This prime move could be a battery operated device, a hand crank, or an air power starter from which you can manually hand pump the air. Then, step by step you must reactivate each part of the system. This can take a while. A lot of systems need to accumulate heat or pressure, so it certainly isn't an instantaneous process." ], "score": [ 9, 3, 3 ], "text_urls": [ [ "https://orf.at/stories/3197056/" ], [], [] ] }

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{ "a_id": [ "goadfsh", "goac88g" ], "text": [ "I did this kind of work! the first step, the good ol' fashioned Mark 1 eyeball. Every couple years an inspection crew can go out and do a visual inspection to check for signs of degradation (like concrete cracking and spalling, rust stains, rusted out metal units). Even if they thing they want to inspect is in hard to reach places, they'll go and look at it with whatever they need to use to get there. The company I worked for specialized in rope-access, or rappelling down the side of the structure like someone rappelling down a mountain. The would head to the top, sometimes with hundreds of feet of rope, and work their way down the sides. Obviously not every situation is going to need to be that intense, and a lot of people are starting to incorporate drones to take pictures/videos, but nothing beats getting there and looking at it yourself. based on the observed conditions, it might be determined that further inspection is necessary. This could stem from things that're relatively simple like taking a core of the concrete (drilling a hole into the concrete and pulling out a section so you can see how it is holding up internally. or a structural engineer could do a structural analysis based on the observed degradation and using estimates for how much each member has been weakened. or, in some cases they could actually do a load analysis. Say take something like a bridge that you're a little concerned about(generally only done for smaller bridges that can go a long time without being looked at, major bridges like the Golden Gate bridge have engineers on staff who are constantly monitoring the structure, this is more for like your small two lane bridge over the local creek). Go out there one day, close down the bridge, and then place a known load on it like a container filled with XYZ pounds of water, and measure how much the bridge flexes/displaces. and use that gathered data to work out how well the bridge is working compared to when it was first constructed.", "You check for cracks in the structure and signs of corrosion or distortion. You may also do laser or optical measurement to check that the various parts are still in alignment and don't show signs that the substructure is moving." ], "score": [ 26, 5 ], "text_urls": [ [], [] ] }

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{ "a_id": [ "gob1nr7", "gob246v", "gob6d4d", "gob1it0" ], "text": [ "Spacecraft aren't trying to go *up* so much as they're trying to go *fast.* Most of the time when you launch to space, you're trying to stay in space for an extended time and not immediately fall back to Earth. This means you need to move horizontally at such speed that the curved surface of the Earth drops away beneath you faster than you can fall towards it. This condition is called *orbit.* It takes around 7.8 kilometers per second of sideways speed to maintain Low Earth Orbit, which is where the vast majority of a rocket's energy goes. This is about eight times faster than the world airspeed record for a jet aircraft. If you tried to accelerate to orbital speeds within the atmosphere, the crazy amounts of drag would slow you down in the same way that space capsules brake during re-entry—enveloped in superheated plasma that threatens to destroy your craft. For this reason, you need to get above most of the atmosphere before pitching over and accelerating sideways—but being above the atmosphere means no air for your jet engines. Since only a small fraction of a rocket's energy is spent on gaining altitude, it doesn't make much sense to construct a hybrid jet-based launch system when you can just carry a bit more fuel for the rocket engines instead.", "> Wouldn't it make more sense to have an aircraft with conventional and high altitude jet engines and a rocket booster in the tail? Some rockets do this, for instance Virgin Galactic is trying to do this with their own rocket, though they are only aiming for suborbital flight. The problem is that most of the energy spent on a rocket is not for the rocket to go up, its for the rocket to go sideways. Being at a high altitude helps, going fast helps, but usually you aren't going anywhere near fast enough to achieve orbit with a plane. The problem is that to achieve orbit you would still have to strap a massive rocket to the body of a plane, far bigger than any plane can handle. At that point, it just becomes easier just to have the rocket launch from the ground, since after all very little of the rocket energy is spent on going above the atmosphere.", "Orders of magnitude differences. * highest altitude for a plane is about 49,000 ft * lowest altitude for orbit is about 528,000 ft The highest plane ever could only get itself to 10% of the way there, with literally 0 lbs of payload. * Fastest manned plane ever is about 7,200 km/h * Slowest orbit is about 28,000 km/h The fastest plane ever could only get itself to 25% of the speed needed for orbit, again with literally 0 lbs of payload. So combined you'd have use the fastest, highest plane ever built and somehow make it carry multiple times it's own weight in just fuel to get the rocket the rest of the way up. No matter how you calculate it, a rocket is faster, lighter, and operates higher than any plane ever built. Thus, it doesn't make sense to use a plane instead of just a slightly larger rocket, especially since you still need a rocket either way. That's all before you consider the volatility of the rocket parts, and you know, the incredibly volatile fuels used.", "Be cause you're only saving like 11 miles tops of the trip by using a conventional craft since wings rely on atmosphere. The ISS is 250 miles up and that *still* isn't quite enough to not require regular adjustments via attached spacecraft to not plummet into the ground, thanks to gravity. Plus that aircraft needs to carry the tens of thousands of pounds of fuel needed to get that high conventionally (and get back home), and then an additional tens and tens of thousands for the rocket. May as well just put that energy into going straight up from the start instead of at an angle." ], "score": [ 32, 5, 4, 3 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gobs533" ], "text": [ "Using three way switches, [like this]( URL_0 ). Instead of having an on/off position, each switch has two positions. Each position in one switch is wired to a position in the other switch. When both switches are switched to \"matching\" position, the circuit is complete and the light turns on." ], "score": [ 12 ], "text_urls": [ [ "https://upload.wikimedia.org/wikipedia/commons/d/d0/3-way_switches_position_2.svg" ] ] }

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{ "a_id": [ "gogrxe0", "gogo7l7", "goh028p" ], "text": [ "The thickness (called gauge) of a wire depends upon how much current it carries. Cables delivering signals as opposed to power use very low currents. There would be no benefit to making the cables thicker. They would only be more expensive and less flexible for no benefit.", "Possibly (as thicker wires have a lower resistance), but they'd also be a lot more expensive. If you make a wire twice as thick, the volume goes up x4. This means the cost of the metal will also go up x4. The thickness they are is fine for most use cases. Just don't mangle them by wrapping them tightly around your arm! Do yourself a favour and learn how to coil cables properly :)", "They are as big as they need to be for the specs of the signal-loss and power. Same as roads, you could turn your street into 8 lane road. You could handle more cars (power) easily but would make the other things more inconvenient. You wouldn't do this unless there are good reasons due to the cost (money and resources)." ], "score": [ 11, 6, 3 ], "text_urls": [ [], [], [] ] }

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{ "a_id": [ "goh6r83", "goh6xd0", "goh6wj1", "goh6vkf" ], "text": [ "Against a smooth, hard surface racing slicks work great. The second they get wet or dirty they're trash. The point of tread is to move water, sand, mud, and other debris out from under the tire so it can make good contact with the road.", "racing slicks are made for dry, flat track surfaces where there's more rubber contacting the pavement. for normal driving conditions that may include rain or snow, you need tread so the tire will grip better and not ride on a film of water. the grooves on normal tires let the water run through and keeps the tire contacting the road surface.", "Treads don't have more grip in dry conditions. The treads are there to give water somewhere to go (which is why Formula 1 cars go to treads in the rain). Slicks are grippy on dry, clear tracks.", "They have some downsides. Any water or gravel on the road and your grip is screwed. If the tires are cold your grip is screwed. Perfect asphalt with warm slicks and you're stuck to the road though!" ], "score": [ 24, 8, 5, 4 ], "text_urls": [ [], [], [], [] ] }

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{ "a_id": [ "gojs8sc", "gol359u" ], "text": [ "You have some incorrect assumptions going in. The biggest factor in power is the displacement (total swept volume of all the cylinders) and the biggest factor in efficiency is the compression ratio. A high compression 6 cylinder can be much more efficient than a low compression 4, and could have more or less power depending on the compression and displacement. A Formula 1 engine is only 1.6L (about the same as a small straight 4 in a car) but it can put out over 1000 hp. A truck V8 is typically larger displacement than a car V8 (larger cylinders and/or larger bore and/or larger stroke). What matters is how much fuel you can burn, which depends on how much air you take in, which is displacement. And how much power you can get out of that fuel, which is compression ratio. You absolutely can have a v6 that's proportionally bigger and has the same displacement as a V8. If they have the same compression ratio, they'll have about the same power and efficiency (minus some more complicated effects related to the extra stuff to make the cylinders work). The size/number of cylinders is mostly about smoothness (more is generally smoother) and speed (many small cylinders can go faster than a small number of big ones).", "It depends on the purpose, and generally how many rotations per minute and torque you want to get out of it. Do you want a low-revving engine with a lot of torque, like for a truck to haul things? So let's take a V6 engine for this purpose, 4 liter total capacity of the cylinders. It would have large-diameter pistons and a long stroke, allowing it to produce a lot of power for each ignition in a cylinder. It would have a lot of torque, but wouldn't be able to rev very high because of the huge masses going back and forth long distances. But what if want to race instead? We want a high-revving engine. So instead of 6 cylinders we use 12, but with the same overall 4-liter capacity. So now that the capacity is spread among twice the cylinders, they are smaller with a shorter stroke. This engine can rev higher, producing more horsepower. This is the configuration used by a lot of old Italian supercars, although they were often much smaller than 4 liters. The original Ferrari V12 was only 1.5 liters (very tiny little cylinders), but it produced about 120 hp back in the 1940s. I didn't hear about four-cylinder 1.5 liter engines' on the market putting out that much horsepower until the 1990s due to advanced engine technology. > A 4 cylinder is going to be more fuel efficient than a v6 because less cylinders = less fuel being used by the engine. Not necessarily, for a given power output. You can have a 2.5 liter 4-cylinder and 6-cylinder. That's a little on the large side for a 4 and a little small for a 6. But that 6 is likely to produce more power than the 4. The big savings here in keeping with 4 is in weight of the engine and cost, and less weight generally translates into using less fuel because you're dragging around less stuff." ], "score": [ 16, 3 ], "text_urls": [ [], [] ] }

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