The correct answer. The question doesn't actually provide us necessary information to be able to answer it. It's meant to be impossible and annoy people.
The wheels will either overcome the coefficient of friction or explode from centrifugal forces, and then the plane will take off like it had skis or pontoons.
The plane pushes the air through its engines which generates force needed to push the plane. The wheels spin at the rate the plane is moving forward the conveyor matches speed.
The conveyor's speed on wheels CANNOT create enough force to slow the jet engines on the plane as they dont need the wheels to do anything other than hold the plane up. They are basically just their to roll.
The jets move the plane the wheels go faster the conveyor goes faster then the plane takes off. Many of you might be thinking, "how when its sitting still on the conveyor" its not... it is moving down the conveyor. Thankfully the conveyor was said to be as long as a runway and the plane reaches speed needed for lift...
The thing is, in order to move forward, assuming the wheels don't skid, they need to spin faster than the conveyor belt. It's a necessity of how wheels work, regardless of force.
The mathematical answer here is that the speed of both the wheels and the conveyor immediately approaches infinity as the plane starts moving. Mathematically speaking, the plane can't take off, not because it is being slowed down or anything, but because a forward moving state of the plane is mathematically impossible, even as the wheels and conveyor spin at infinite speed (because it's still equal). This is to say the plane won't be there struggling to take off, the next moment where the plane accelerates just can't happen. Effectively, time can't progress.
Physically speaking, as the wheels and conveyor belt accelerate towards infinity, there will be an equilibrium where the friction of the wheels' bearings completely counteracts the thrust of the engines and the plane stays in place. If this were a real situation, those bearings would melt from the insane heat (this is assuming the hypothetical conveyor can handle this speed). With that said, if we allow a strong enough headwind, then the plane can just take off at zero ground speed, lifting off vertically, since this hypothetical wind is as fast as the plane's required airspeed for takeoff.
Yeah, pretty fucking insane to come to the conclusion that it's mathematically impossible because their speed would become infinity instead of just, you know, wheel slip.
But wheel slip would slip violate the idea that the wheels are moving at the exact same speed as the conveyor.
The engines could push it forward and the wheels move faster, or they could skid and move slower... but they basically couldn't possibly match, which is an assumption of the question
I think that's the point, the conditions in the question are not possible. The speed of the wheels and speed of the conveyor cannot be equal.
That's a condition that cant exist.
You would find that the conveyor, based on its size, would generate enough wind needed for lift at speeds that would be needed to seize the bearings. So even if you mathematically work this question, the plane takes off.
Depends on the mechanics of the engines and wings. Even if the plane is forced to stay perfectly still due to infinitely spinning wheels against infinitely spinning treadmill, that treadmill itself would generate airflow, or at least it would be compatible with airflow. Airflow under the wings lifts the plane. It could easily takeoff or at least should be possible and that's not getting into different airplane architectures where the jet itself provides the necessary airflow without needing the plane to be moving relative to the ground. Which this isn't, but would be another way to bypass
The wheels are free-spinning. They don't put a backwards force on the plane when they spin, or if they do it's a tiny fraction of the force of the jet engine and is easily overcome. All the conveyor belt does is somewhat increase the rate of the wheels spinning as the plane is accelerated forward via the engines.
As others have said, at some point the plane doesn't care if the wheels are spinning or not, it's going to move forward. The wheels will just slide instead of spinning
ok, but sliding also has friction. and work lost in non-relativistic cases is proportional to the belt speed.
so you can always increase the belt speed enough to lose all turbine power.
You can increase the speed, at some point fluid dynamics will simply force the wheels to hydroplane on thin air. Aerodynamic Levitation. The thin film of air that the conveyor drags with it will seperate the tire from the conveyor and the plane will slide along the surface.
The plane takes off just like normal, only difference is the wheels spin twice as fast as they otherwise would. This has basically zero effect on the plane
Fair… kind of. The air will push the plane forward regardless of the treadmill so the speed of the plane will generate lift with the air. So… yeah I missed a step
The tyres aren’t doing anything on a plane. They just spin freely. the tyres contribute nothing to a plane’s acceleration, they’re just holding it up. It wouldn’t matter if they were spinning backwards, the jet engines will provide the thrust and the wings the lift. It doesn’t matter what the conveyor belt is doing.
Yes it can. A plane generates lift by having the air pass over the special shaped wings which turns horizontal force into vertical force. It doesn't make any difference whether the plane is moving forward at 300 km/h, or the wind around it is moving backwards at 300 km/h.
The conveyor is the one that needs to match speed with the plane. The plane will start moving forward regardless of what the wheels or the conveyor are doing, and even if the conveyor perfectly matches wheel speed the whole time, the plane will inevitably just start sliding on the conveyor surface.
The jet engines will take care of that. They will push lots of air out the back very fast. This will make plane go forward, which will allow air to go over wings. Wheels are only there to reduce friction.
The issue is the question is worded poorly. The conveyer will never “exactly match the speed of the wheels” once the engines thrust start overcoming static forces.
Freely spinning wheels means plane starts moving forward, wheels spin to match its speed, if the conveyer tried to match the speed of the wheels, the wheels would then have to go faster to both match the conveyer and keep up with the momentum of the plane, which makes the conveyer faster, which makes the wheels faster etc etc
There's the third option of "the conveyor moves so the wheels don't spin at all", but that would require the conveyor belt to move the same speed and direction as the body of the plane, and I doubt that's what anyone meant.
It’s a somewhat ill-posed problem that misrepresents the physical system. The idea is that the treadmill always matches the speed of the wheels. This can’t actually happen, so it’s hard to intuit about what would happen if it did.
In a slightly more real system, the plane receiving any forward impulse would cause a feedback loop between the speed of the wheels and the treadmill until the wheels were going infinitely fast or exploded.
In a slightly more real system, something funky beyond my understanding of physics would probably happen as the wheels approached the speed of light and that might affect the outcome.
In a slightly more real system, skin drag on the surface of the treadmill would eventually give the plane enough airspeed to lift off even if the treadmill successfully prevented it from gaining any ground speed.
Except the treadmill isn't at 50 mph, its speed rises as the plane tries to go forward, it matches the angular velocity of the wheels exactly ( v = ω × r ).
So the wheels spin freely until the bearings melt.
If we are imagining a runway sized treadmill that can hold a plane for a thought exercise, I believe it would also imagine frictionless wheels. In that case, they do not impart any force onto the actual plane, and the force is produced by the jet engines pushing air out the back.
The plane pushes off the air, so the conveyor belt would not be physically capable of holding the plane in place. It will just make the wheels spin faster.
The wheels spin faster in one direction, and the conveyor belt spins faster in the opposite direction. The plane itself remains stationary, regardless of the engine thrust.
The engines are pushing against the air, they don't care what the wheels are doing. The wheels are only there to minimize friction. In this scenario, they're coming into play if the wheels spin so fast that they melt the bearings.
But if we're assuming a runway size treadmill, I think we can assume frictionless wheels, which means it doesn't matter how fast they spin.
With that logic, the plane could be chained to a post, and once the engine are up to speed the plane would lift off of the ground.
These aren't rockets, the engines have to care what the wheels are doing; they don't have enough thrust to lift the plane from a stationary position.
The next time you're at an airport, watch the planes from a dead stop; they start slow and build up speed down the runway. As the plane moves forward, air travels faster over the top of the wing than underneath it, creating lower air pressure above and higher pressure below. The conveyor belt would prevent any speed increase, thereby preventing lift.
I literally test engines for a living, I know what they're doing.
And as far as the wheels are concerned, why would rockets be different from jet engines? They are both exhausting thrust out the back, does it matter if it's from atmosphere or if it's from a chemical reaction? Neither one affects the wheels.
Rockets, as well as planes, start off slow and gain speed. That's how Newtonian physics works.
The problem is that you're ignoring his position. No-one is debating what the engines do. They push against the air, yes. shavertech is saying that 'the conveyor belt cancels the plane's forward movement' - just the same as if the plane was chained to a building and couldn't move forward, for example.
Rockets, and planes, start off slow and gain speed and then take off, as you said. But if the plane never moves forward then it doesn't have the chance to gain (horizontal) speed.
So the question is, would a plane that never moves forward take off? Or do jet engines that are chained down for testing routinely fly away because stopping their forward movement doesn't do anything?
Sure. Take it up with the author of the original question.
The reason this is always so controversial is that it is predicated on an impossible condition (the belt matching the speed of the wheels). And for some reason instead of recognizing that, everyone assumes that "wheels don't make the plane go" is the missing information.
It depends entirely on what your assumption about the "conveyor is designed to move at the same speed as the tires" means.
If you assume it means the treadmill moves backwards at the same speed the plane moves forwards then the plane moves forwards and takes off with the wheels spinning twice as fast as normal.
If you assume the treadmill exatcly matches the rotational speed of the wheels and you also assume the plane has infinite thrust. then when the engines kick on both the treadmill and the wheels accelerate to infinity and everyone dies in a fiery cataclysm as they both breech the speed of light and tear apart the fabric of reality. But if you ignore that part (or don't assume infinite thrust) then the plane would not move.
It's a problem designed to cause arguments because everyone assumes everyone else is using the same baseline assumptions they are and further assumes everyone else is just dumb for not agreeing with them.
You dont need infinite thrust for the fiery explosion situation to happen. As soon as the plane starts to accelerate, the treadmill will start speeding up, but since this does nothing to impede the thrust of the plane, it will just continue to accelerate to infinity.
If you assume both the treadmill and wheels are perfect in that the treadmill can accelerate infinitely and the wheels can spin infinitely with no resistance, the plane takes off anyway because no matter what the treadmill does the wheels will just spin faster but since they have no resistance that will do nothing to the plane. If you assume the wheels can fail, then the treadmill will start to spin infinitely until the wheels fail and the plane breaks down and explodes. If you assume the treadmill is at all realistic, then it will require time to spin up and it will probably not be able to spin the wheels to the point of destruction before the plane takes off.
There is absolutely no situation whatsoever in which the plane is simply held in place. Either it takes off, or the treadmill is so powerful that it destroys the plane. Its a simple question of forces; the engines of a 747 impart over a meganewton of thrust, in order for the plane to hold still an equal force must be impacted on the plane from the opposite direction, and there is no way you can impart a meganewton of force on the body of the plane through its wheels without either the treadmill or the plane failing.
Its tempting to take the "fully ideal" case and assume nothing can break, but if you do that, numbers just end up going to infinity immediately. As i mentioned previously, the simplest, most ideal model for the wheels assumes that they have no resistance between the wheels and the plane, which means no mechanism whatsoever by which the treadmill can impart any force onto the plane. You just get infinitely fast wheels and treadmills which isnt a very satisfying answer to the hypothetical.
The wheels on a plane don't drive, the thrust from the engine pushes the planes bulk forward, the wheels underneath can spin at one hundred miles an hour and that plane would still take off.
The conveyor belt and the wheels don't matter. Since the forward force is generated by the turbines and not the wheels, the plane is simply dragged forward and the wheels are forced to spin faster than the conveyor belt.
The myth busters did this myth with a much smaller plane. The plane still needs enough runway to take off though. So if in front of the conveyor belt is just a big wall or something, the plane will move forward until it hits the wall.
The original problem is the belt will match the speed of the wheels, and the belt is as long as a runway.
In the original problem as described the plane will take off.
The second paragraph is a discussion on variations, since the problem is already answered in the first paragraph.
Now that you understand why this entire problem is stupid,
Here is my take:
Vb (belt speed ) Va (airplane speed) Vw(wheel speed)
We get: Vb=Vw
And we can make a simple equation to describe Va: Va=Vb-Vw
But by combining the 2 equations we get Va=0
So we can mathematically show that the aircraft can’t move.
Now we actually have to find a way to make sure a situation like this can exist:
We can do this by adding a moment of inertia to the wheel, so what’s basically is happening is the airplane is pushing against the belt that is pushing with the same force back, and only thing that is accelerating is the wheels and belt, o made a diagram below:
"The airplane/treadmill problem...contains a basic ambiguity, and people resolve it one of a couple different ways. The tricky thing is, each group thinks the other is making a very simple physics mistake. So you get two groups each condescendingly explaining basic physics and math to the other." -the xkcd guy
It's funny, mythbusters did an episode on this ages ago and literally the first sentence they said was "well of course it would take off, this is stupid" and lo and behold it did
If you bring up that mythbusters episode, be prepared for people to say the experiment proved nothing, because Adam himself still gets messages about it.
In fairness, they didn't really test anything that was fully in the spirit of how some interpret or describe the meme. They couldn't build a conveyor or really match the impossible mechanics of a thought experiment because it can't really be built as described. It's just not possible.
No it wouldn't. The aircraft is under 4 different forces at any moment. (Under a simplified model) T the thrust is necessarily be equal to the drag (D) generated by the conveyor belt on the wheels. This is the basic hypothesis of the problem. The speed of the conveyor belt equals that of the wheels. This means that theres a non-negotiable fact that the aircraft remains stationary. Other forces are the weight of the aircraft and the force equal to it which is the reaction of the wheels against the ground.
Now since the aircraft is stationary relative to the earth and therefore the airflow, there's absolutely no lift whatsoever, the aircraft won't take off.
Yes the speed of the wheels itself doesn't matter but the conveyor belt makes the aircraft stationary.
If that were to happen in real life i would assume since in reality the engines are a few meters above the ground and the drag is mainly transmitted through the main gear, that either the wheels would pplop or the nose gear would give up due to high anticlockwise torque (if we take the image as reference)
because thrust from engines is entirely independent from airspeed. Given that jet engines effectively suck air in and push the air out faster. If the airspeed mattered for the engine's forward thrust, then they'd never start up or move to begin with. 0 + 15 = 15, so you have jet exhaust pushing against the air behind the engine. All that needs to happen for take off is for the thrust of the engine to outpace the friction of the conveyor, and it'll move forward and take off.
I think the drag from the wheels is only insurmountable if the pilot forgets to disable the brakes. The moment they release the brakes, wheel friction suddenly becomes a tiny component of drag, and the equilibrium is broken, allowing thrust to win.
Yeah technically friction within the bearings of the wheels exists but if we’re assuming a conveyer belt that can perfectly match the wheels’ speed, i think it’s only fair to write off ball bearing friction.
If it's the ground speed of the wheels rather than their rotational speed that the treadmill matches, then there's no issue: the rotational speed will just be twice their ground speed, and the plane will have no issue moving forward.
T the thrust is necessarily be equal to the drag (D) generated by the conveyor belt on the wheels. This is the basic hypothesis of the problem. The speed of the conveyor belt equals that of the wheels. This means that theres a non-negotiable fact that the aircraft remains stationary
You are misunderstanding how planes work. Imagine a small scale. The plane generates thrust by accelerating air backwards, so the forward thrust is acting on the propeller/jet. Imagine pulling an rc plane down a treadmill that is accelerating. No matter how fast the treadmill gets you can still pull the plane forward (until it gets too fast and the wheel bearing melt/tires blow).
I am a pilot. Airplane wheels do nothing. How fast theyre spinning means nothing.
But "up to speed" is relative to the ambient wind speed, if the plane is stationary for everything other than the motors and the wheels, this will never happen
The engines aren't literally accelerating though, acceleration requires a relative position on earth, and it is stationary, the blades of the turbo are accelerating, yes, but the engines themselves are only accelerating relative to the belt of the treadmill
To clear things up, the point is that since the wheels aren’t what’s pushing it forward, the conveyer belt is irrelevant. It will move forward even though the wheels are being pushed against as the wheels aren’t necessarily for the forward thrust to get air under the wings. It won’t be kept in place by the conveyer belt
Oh we're working from different interpretations of the question I see, i took it as absolute speed of the wheels relative to the earth, i.e. the speed of the plane, you guys took it as the speed the wheel turns, like the speed of the point of the wheel in contact with the conveyor?
More so just that a conveyer isn’t able to stop a plane due to how it’s propulsion works. Its like dragging a toy car across a conveyor belt. The wheels are going to be spinning in the opposite direction of what would propel it forward, but it has no real impact on you dragging it because the force is coming from a source other than its wheels
Even if it does that, it just means the wheels spin faster and faster as the plane accelerates forward but that doesn't put any force on the plane itself. So either the plane takes off or the wheels fly apart and the plane and the conveyor destroy themselves.
When the plane moves. The engines accelerate the plane, this cause the air to move over the wings, this generates lift. I do not see how the belt changes any of this
You're saying this causes air to move over the wings, but it doesn't, air is not moving over the wings at any point, air is moving through the engine but the inlet of an engine is in front of the wing and the exhaust is behind the wing
I'm not quite sure what part you're getting stuck on but nothing prevents the plane from moving. The plane will accelerate like normal, and depending on the interpretation of the question, the wheels would be either stationary or about twice as fast as normal, but otherwise nothing changes. I'm not sure why you think the wheels are so important when a plane can literally take off with the brakes locked and the wheels not moving an inch (ignoring the likely popped/burning tires lol)
It's a trick question because the conveyor belt can't make the plane stationary in any realistic setup. Even if the conveyor belt is going 1000 mph backwards, the plane can still take off almost like normal, as long as the wheels don't break.
The rolling resistance of the wheels is roughly independent of the speed at which the wheels are turning, so if it takes F units of force from the engines to make the plane start going forwards on a normal runway, it will still take about F units of force from the engines when the conveyor belt is going at 1000 mph. So the wheels will start to turn faster than the conveyor belt regardless and the plane goes forwards.
Because the jets just push the plane forward into the wind, it's that wind that causes the plane to go up, if the plane is not moving forward relative to the wind, it won't go up
That's the ground contact of the plane. We're assuming a magic conveyor here that can push an entire plane back with hundreds of kN of force pushing the plane forward
Because it's not the jets themselves that give the plane speed, its the air rushing by.
Compare running freely to running on a treadmill. If you run freely outside, air rushes by right? If you run on a treadmill, you move with 0 velocity relative to the earth, thus no air rushes by.
Yeah but the treadmill will not stop the plane from moving: imagine you're on a treadmill with roller blades tied to a rope. You'll be able to pull yourself forwards along the rope regardless of how fast the treadmill is moving.
It is a question wrongly put. The engines move the plane by pushing on the air, not the ground. If the ground is moving fast enough that the wheels are generating enough friction to keep the plane still then the wheels will break and eventually, melt. At the point they are liquid they will no longer be able to stop the plane from moving anyway.
What nobody ever mentions about that interpretation is that the conveyor belt and tires would need to be able to spin up to an infinite speed without tearing themselves apart/creating a singularity.
The problem is that the interpretation where the speed is 0 is physically impossible. The treadmill would need to spin to infinity since the wheels are independent from the source of acceleration (the engines).
Think of it this way. If we shrunk the scenario down, and the little plane was on a little treadmill. If you pulled on the plane with a rope, while the treadmill was moving under the wheels, could you still pull the plane?
Yeah no I know, I'm just saying if they're entirely wrong it's still "an interpretation" so my question was answered (I am the commenter like 3 comments up that asked "what interpretation [...]")
(Also technically if you account for friction from the wheel bearings you can reduce the required speed to a finite amount, but then you'd probably just break the wheels)
IT is not. The wheels are. That's like holding a wheel on your finger against a treadmill and then claiming you're travelling at 20mph. The rotation of the wheels is completely irrelevant to the movement of the aircraft, other than reducing resistance relative to just sliding on metal skis or something
Right, but why is Va = Vw - Vb? The airplane is being accelerated by the engines, which work by pushing air back, if the wheels affected the speed of the aircraft they wouldn't be very good wheels
it comes from basic Newtonian physics and from describing the wheel speed.
on a normal runway, Vb = 0 so Vw = Va thats prety understandable
on a a belt moving at Vb the speed between the belt and the aircraft is Va + Vb
so when we describe the wheel speed on the belt we get Vw = Va + Vb
then we just solve for Va and we get: Va = Vw - Vb
even in a normal aircraft the wheel speed is always directly related to aircraft speed. (and they effect the speed of the aircraft because they have mass and moment of inertia) but in the real word, we don´t have magical treadmill based on the airplane wheel rpm.
The issue is that Vw isn't a constant, the airplane is moving independently of the wheel speed, Va is the constant (as Va is determined solely by engine power, assuming wheel bearing friction is negligible). Vw would just be equal to Vb + Va, whatever those two happen to be
The speed of the airplane relative to the ground affects the speed of the wheels, not the other way around
First a bit of nitpicking, Nether are a constant. They are 2 variables, and they are mutually dependent through a rolling constraint. That’s quite well understood part of mechanics, and it works both ways and always did. It really doesn’t matter where the driving force/moment comes from. If One is slower, the others one also has to be slower. And wise versa. Just like 2 meshed gears doesn’t meter which one is driven, the gear ratio is still the same, and if one slows down the other one will always slow down as well.
Only reason I didn’t do it in angular velocity is because I wanted to keep it more simpler. And describing it properly would be annoying.
But let’s do it properly right? (Spoiler we will get the same answer)
v (velocity of the aircraft relative to the belt)
va (aircraft velocity relative to origin)
w (angular velocity)
r (Wheel radius)
vb (belt velocity relative to origin)
What we described in the original as wheel speed Vw is just w*r
So we will rewrite it as vb=w*r (1)
The rolling constraint says: v=w*r (2)
And clearly v=vb+va (3)
Then we will combine (1) and (2) =>
v = vb (4)
And if we combine (3) and (4) =>
vb=vb+va =>
0=va
Any other way you try to describe the wheel speed, you will always get va=0 from it.
And you can even find a force that will oppose the motion IRL, it’s the moment of inertia. and as the belt will be accelerating the wheel. The belt will be pushing the airplane back with the force identical to the thrust force from the engines.
Here is a diagram to show: how you could calculate the wheel acceleration nesasary to cancel out the thrust force:
It doesn't matter. The moment the wheels are moving, it's being pulled backward by the conveyor. The jets don't make it fly, movement through the air does. It doesn't matter if the engine is going fast enough to accelerate to 300mph, it's not moving through the air and the wings don't get any lift.
Why would the wheels being on a conveyor belt stop the plane from moving? The wheels will simply spin faster until they melt and are no longer a problem.
Now that you understand why this entire problem is stupid,
Here is my take:
My assumption: wheel speed is base on rotational speed of the wheel, not its linear motion and the thread mill is moving against the direction of the plane.
I made these assumptions, because all other options are trivial.
Now assuming infinite friction so the wheel can’t slide,
Since the wheel speed is instantly matched by the wheel speed, Vb (belt speed ) Va (airplane speed) Vw(wheel speed)
We get: Vb=Vw
And we can make a simple equation to describe Va: Va=Vb-Vw
But by combining the 2 equations we get Va=0
So we can mathematically show that the aircraft can’t move.
Now we actually have to find a way to make sure a situation like this can exist:
We can do this by adding a moment of inertia to the wheel, so what’s basically is happening is the airplane is pushing against the belt that is pushing with the same force back, and only thing that is accelerating is the wheels and belt, o made a diagram below:
The phrase “exactly match the speed of the wheels, moving in the opposite direction” is intentionally misleading and this problem is unsolvable. It’s known to be unsolvable.
Ask yourself: direction opposite to what exactly? If you think you know the answer, it’s coming from an assumption you made and not the wording of the question itself.
Whether the speed is rotational or translational - it affects the outcome. I, for example, first assumed it was rotational, meaning that the jet (or any part of it other than a point on a wheel) would not move relative to a point on the ground and therefore would not experience airflow. However, this could cause the rotational speed of the wheels (and the treadmill's speed) to approach infinity. If it's translational, the takeoff works (in theory).
Plane doesn't move (except for wheels)
Wings don't move (by extension)
Wings basically are irrelevant for this scenario without airflow
Engines don't produce enough thrust to lift this plane without wings (~1MN vs. several MN)
In other words, 100% of the kinetic energy goes into the wheels spinning faster and not moving the whole plane. Or, if the wheels rotate one circumference, the belt the plane was resting on has moved back one circumference of distance (already shown by animation though).
I know that this interpretation is the rarer of the two perhaps and am not trying to say it's the "right one."
The wheels are what I'm hung up on, I disagree with the interpretation, but I would still like to understand what people who don't are arguing
I think the question that's raised for me is how do we get a scenario where this translate into 100% of the energy produced by the engine going into the wheels?
I don't see how the wheels spinning backwards prevents the plane from taking off. The backwards pressure on the plane from the treadmill would never equal the engine thrust.
The treadmill would have to be exerting backwards pressure significantly over what it would take to be only equally counter rotating the wheel, surely
I feel like the only way that interpretation makes sense is if you imagine the brakes are on
i just re-read the scenario, and I think it might just be because the setup is physically impossible. The "matching the exact speed of the wheels" part implies that the conveyer belt can keep accelerating until the rolling resistance equals the force created by the engines
The thing I don’t get about this is. Why would this affect the speed of the plane at all. The plane wheels free spin they wouldn’t move the plane backwards. That’s like expecting a shopping cart with a rocket strapped to it to stay still just because you sat it on a treadmill going the same speed as it backwards. ITS NOT GLUED TO THE DAMN TREADMILL, FRICTION CAN ONLY APPLY SO MUCH FORCE
Mark Rober has a video where he puts a model plane on a treadmill and it sorta doesn't go anywhere. Take from that experiment what you might. I think those that interpret the conveyor as conteracting any forward motion of the plane are think along that line. As the meme is worded, some take this as a recreation, but then the question/meme is worded to make people make snap assumptions. Actually building an experiment as described in the meme is impossible. So it will continue to be argued about.
Wouldn’t this result in the plane struggling to move as the wheels spin freely until they break at which point the plane would fall?
I say this because the plane has to move to get lift, and with the conveyor belt pushing it back slightly it would probably not be able to get enough quick enough (despite still moving against the conveyor belt by dragging the wheels).
A bit off topic, but I've heard that there was a place that had an engine in the wheels...
it was not to move the plane on the ground tho, it was actually to spin the wheels right before landing, because in most planes, hen you land, the wheels aren't spinning until they touch the ground, and when that happens, friction is so high that it burns part of the wheels, so they need to change them very often, and adding an engine to spin the wheels would help with that. It didn't really help, landings still burned part of the wheels, not as much, but still wore them down, and adding an engine there is really, really complicated, so that's why it isn't used in most planes
Holy hell a lot of people in here are extremely confident with only half an understanding of physics and how planes work. The external force pushing the plane forwards comes from the engines, which are NOT the wheels, so the wheels will just be moving faster (along with the treadmill) as the plane itself is propelled forwards by the engines until it is going fast enough to have enough lift for takeoff. The plane will still love down the runway, as the wheels are there to reduce friction, not speed the plane up on takeoff. It would just result in the wheels and runway turning MUCH faster than the wheels would normally turn for takeoff, it wouldn't keep the plane stationary
the conveyor belt doesn't modify the speed of the air around the plane though? it'd just make the wheels spin twice as fast, but the plane's airspeed will still be the same as if the conveyor wasn't there
It wouldn't. It's sitting on the conveyor, sitting meaning stationary. So if the plane is stationary it can't lift of. The moment it starts accelerating, it's no longer stationary and thus break the premise of the question
But it isn’t stationary. The plane engines are on.
Assuming no friction, the issue present here is that the conveyer can only match the wheels if the plane is stationary. Any force that doesn’t require pushing off the ground breaks that.
However simultaneously it asks if the plane can take off. But plane engines generate force doesn’t push off the ground, thus breaking the previous requirement.
Either this asks if a plane will take off when the engines are off, which obviously no but also completely disregards the existence of the conveyer and means that “will the plane take off” is incredibly misleading as it makes anyone assume the plane is trying to take off which means engine power.
Or it is literally asking something logically impossible. Making no more sense than asking if a car A will overtake car B when car A is going faster than B but B is going as fast as A
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u/qualityvote2 🤖Suspected as Bot🤖 6h ago edited 21m ago
Good news, the community has decided that this IS an antimeme!