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Here's the classic:
Question #1: If a 747 is sitting on a conveyer belt as wide and long as the runway and the conveyor belt matches the exact speed of the wheels moving in the opposite direction, can the plane take off?
Here's the new part:
Question #2: Is there a speed that the conveyor belt
could move to keep the plane from taking off?
Saffir–Simpson scale
https://en.wikipedi...%80%93Simpson_scale
[Voice, Dec 06 2024]
Do this thing to the wheels and it’s not taking off.
https://youtube.com...si=wgdRRGYUOg1FDm86
Do it before the jet has time to accelerate forward. [doctorremulac3, Dec 07 2024]
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the answer, my friend, is lying in the wind |
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I always answered that the plane would take off, reasoning that the treadmill would pull enough air along with it. Others, not having reasoned that far along, assumed I just don't understand physics. The same has happened to me with the "open refrigerator in a room" question. It has a motor: of course it's going to heat up the room. What pisses me off the most is when I think a question like that through, give the "wrong" answer, and then support my answer and people think I'm spitballing to get out of having answered wrong. It really twists my willy. |
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Question 2 depends on whether something is keeping the plane from moving backwards, such as its engines. If the plane doesn't move backwards then it will face ever-increasing wind as the treadmill pulls air toward it. If the friction on the wheels exceeds the power of the engines before take-off it will need some extra help to not move backwards. |
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Do you mean linear speed or rotational speed? |
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Also vertical speed. If the treadmill rises with the plane as the plane reaches takeoff air speed has the plane taken off? |
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//Do you mean linear speed or rotational speed?// |
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That first one isn't mine, and I'll just say that was my question exactly. Rotation is stated in RPM, so when you say "speed of the wheels" you're talking about linear whether or not that's what they meant when they wrote this. |
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As far as the floating treadmill that is a new take on this and kind of gets to the point that this nerdy quiz can actually get kind of fun. For instance, can you ask questions that make the puzzle maker confused? |
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This question represents a failure to understand why aeroplanes can fly. All flight occurs as a result of the difference in moving air pressure above and below the wings due to their curved shape. Planes are literally sucked into the air. No matter how powerful the engines are, if the plane doesn't move relative to the air, it's not going to fly. Of course, if it's a Boeing, it's time in the air may be relatively short and have a catastrophic ending. |
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what [xenzag] said, or Kansas through <theircompetitor> in the first annotation |
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I reiterate, I was talking about air being pulled along from the movement of the treadmill. //as the treadmill pulls air toward it// |
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if a Cat 5 hurricane provided a continuous wind in a perfect direction, an aircraft would not need a runway to take off |
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//This question represents a failure to understand why aeroplanes can fly.// |
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No, a wrong answer represents a failure to understand why airplanes can fly. Your evaluation represents a misunderstanding of how questions work. |
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Anyone get how the treadmill can keep the jet from taking off? Here’s a hint: it can. |
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// if a Cat 5 hurricane... // |
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An interesting proposal.
1. Place airplane in hangar. Start engine.
2. Open hangar door. Increase prop speed to move airplane out into the oncoming wind.
3. Once clear of the hangar pull yoke back and plane rises upwards. |
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It really can't, there are engineering and funding limits that prevent a conveyor belt being built that big. |
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the rotation of the of the wheel is mechanical, and unpowered. I fail to see how the speed of that rotation is relevant in any way. it's rotating because the plane is moving, not the other way around. So there's no scenario where it robs the plane of motion. |
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Unless it acted as a breaking agent with its friction coefficient being so high that it slowed the plane |
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Think of one of those devices where they show cars as they revv up while standing in place |
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Such a device would make no impact on a plane taking off. Only somehow acting as a break would. |
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But to complete the logical experiment, a car will NOT take off even if in theory it would have on the road -- because it's not getting airflow so the body can't act as a wing |
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lol there's nothing else either the treadmill acts as a break or the plane takes off |
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Right, so to answer question #2, how could the treadmill keep the plane from taking off? |
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any speed that prevented free rotation of the wheels would work but could be compensated as power continued to increase, ultimately friction is not sufficient and actually plane would STILL take off. But assuming ideal friction conditions then it would be anything that keeps plane speed under takeoff speed, adjusted negatively |
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like it doesn't have to be zero, just has to be slower enough than the plane and thus breaking the wheels |
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Okay, here’s the answer: the treadmill goes from zero to fast enough to cause the tires to explode before the jet has any time to accelerate. A few thousand miles per hour or so should do it. Then the tireless wheels are destroyed by the treadmill burning out the bearings so the wheels fall off and what’s left of the landing gear gets ground to pieces till it collapses and the plane crashes onto the treadmill that’s now become a jet grinder where it too is torn to pieces. |
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//how could the treadmill keep the plane from taking off?// |
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At a high speed the wheels can't spin fast enough. The plane starts to move backwards on the treadmill, meaning the air picked up by the treadmill isn't moving fast enough relative to the plane to lift it off. This doesn't apply if some other force is countering that friction, but the friction increases with the speed. At some point the wheels will explode and the plane will be resting on its landing gear supports. Then unless the plane is being pushed forward against the friction and stabilized it will start to move backwards at the speed of the treadmill. The only air flow is the air moving somewhat slower than the treadmill, so a plane moving backwards with that wind can't take off. |
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Exactly. We think of the wheels as being frictionless but that’s not the case, especially if you start spinning them beyond their design limits. Let me find a video of rubber wheels being spun so fast the expand and eventually explode. |
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I’ll add this, I’d have a spinning kinetic energy module get up to as many RPM as possible then grab the treadmill causing it to accelerate so fast the tires basically get destroyed instantly before they even get a chance to turn. |
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Didn't Mythbusters do this one? |
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So the "solution" is to destroy the plane? That's like saying "the solution to this maze is to burn the maze down & walk straight out".
Also, "the conveyor belt matches the exact speed of the wheels moving in the opposite direction" is impossible (ignoring the "so fast everything explodes" scenario) - as the plane has (or gains) forward speed relative to the fixed frame of the conveyor, the conveyor can NEVER match the speed of the wheels as the wheels have the plane speed as an addition to the conveyor speed.
AND, if the conveyor moves fast enough that there is a large boundary layer of air moving with it, that will HELP the plane take off, not hinder it. |
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//the solution to this maze is to burn the maze down & walk straight out// |
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That's this conundrum solved. |
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If the wheels and landing gear disintegrate and the engines and wings are smashed to pieces, the plane’s takeoff will be iffy, regardless of any air moved by the treadmill. |
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The propulsion system pushes against air not a runway. Gain enough thrust and a friction-less runway will still allow for take off. |
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Move an infinitely long runway in reverse just a bit too fast for the plane to make headway and it will eventually push against enough air and still take off... unless you wreck the plane with the runway like you said. |
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I remember when I read the first one that I didn’t write, I was confused because it was like, “Are they asking if turning the wheels in some direction with a treadmill affects the tons of thrust from the engines?” |
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Good follow up question after the first one to help illustrate the answer might be “How about a plane on pontoons taking off moving upstream against a raging river?” Give an example where it might NOT be able to take off if the water were moving fast enough relative to the power of a say a little prop engine, then point out the difference in friction between a set of massive pontoons getting slammed hard with tons of water and a few wheels on lubricated bearings. |
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Make it a learning thing. |
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Can I ask you guys a question? |
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I don't want to post it as a thing of its own and I wouldn't normally ask on almost anybody else's postings, but I hope [dremulc3] is amenable. |
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I keep seeing these test your IQ tests popping up. |
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Every once in a while I will take one. |
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I ace them every time. 100%. One time I fed my dog and took a shit before finishing and still aced their test with a run under 97% (according to them), of the applicants. They then want money to authenticate my score. |
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I never finished high school. I survived.
I have no idea how smart or stupid I am on the academic scales. |
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Any of you guys know a legit way to find out without getting bilked? |
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Sorry to hijack your posting for that request [drmlk3]. Minor segue. |
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I took a MENSA entry tests many years ago and not only got a high enough score to join, but scored the correct answer on the bonus question: “Will you give us money to join MENSA?” |
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The first test in qualifying for MENSA membership is in proving that you have not completed any tests for joining MENSA. |
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I recently asked ChatGPT to compare my writing -- who would it pick. |
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It gave me Vonnegut, Terry Pratchett and Douglass Adams. |
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So I'm even more sure I'm a genius. |
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The IQ tests are a scam to get a subscription. Or in other words, a way to prove that even smart people will let their egos get the better of them. |
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//The first test in qualifying for MENSA membership is in proving that you have not completed any tests for joining MENSA.// |
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So anybody who takes an IQ test is stupid. Well, that gets a 100% for originality at least. Taking it is one thing, paying money afterwords is another. |
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Back to Earth for a second, IQ is an interesting thing. First of all, it can be of little or no relevance if we're talking about applicable utility. It's a facility that was inherited and the only way to gauge its usefulness is by how effective its application in the real world has been. The real test is the efficiency of the transmission of this raw potential to figure things out correctly. It's like the horsepower of an engine. If there's not an effective transmission system, it's useless. I call that "latent intelligence vs applied intelligence." The transmission analogies would be hard work, attitude, organization, planning etc. |
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I'm more impressed by a lower IQ person with drive and determination that does amazing things than I am of a high IQ person that sits around pontificating and judging others all day while their "inferiors" make the world work. |
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it makes one hell of a difference statistically. It makes very little difference individually. As you would expect from a statistical measurement. It winds up both reinforcing and explaining our prejudices. Not justifying, mind you -- explaining. |
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Exactly. A high IQ, a dime and a time machine will get you a cup of coffee, but ironically, if you want to design a space launch system you'll do better with the cumulative works of a high IQ bunch. |
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