What is Digg?914 Comments
- Otto, on 10/12/2007, -24/+264Planes don't move by applying force to turn the wheels, like a car does. The forces produced by the engine act directly on the body of the plane itself.
So the treadmill would have little to no impact on the movement of the plane down the runway. All that would happen would be the wheels spinning twice as fast as normal. - inactive, on 10/12/2007, -175/+306Are you guys ***** retarded? You need wind over the wings to fly, and putting the plane on a treadmill doesn't put wind over the wings.
Holy *****, you people should just shoot yourselves. - Otto, on 10/12/2007, -8/+100>>>"A lot of you seem to be forgetting that it's a 2 stage system for that plane to take off."
No, it's not. Airplanes don't have engines hooked to the wheels. The wheels are free wheeling, the only thing hooked to them is brakes, and those aren't used much.
Airplanes derive all of their motion, whether in the air or on the ground, from the engines pushing the body of the plane against the air surrounding it. Jet engines take in air at the front and expel gasses at high speed out the back, thus thrusting forward. Propeller engines suck air in front and push it backwards, thus thrusting forward. The wheels provide no thrust whatsoever.
The force is not applied to the wheels. It's applied to the body of the plane. - feylanks, on 10/12/2007, -33/+117monolith2 - you (and all the people digging your comment) have a poor understanding of this. OF COURSE JUST SITTING ON A TREADMILL WONT GENERATE WIND AND THEREFORE ANY LIFT. ***BUT*** the plane will not "just sit there" because the treadmill will not keep it in the same place. it will continue accelerating as if it were not on a treadmill because
(READ HERE NOW NOT LATER NOW)
the treadmill doesn't detract from the ***** jet turbines or props pulling or pushing the plane through the air.
damn you people and your poor understanding of the world around you. - mt066, on 10/12/2007, -3/+55It's hilarious how much this is pissing everyone off.
- butch81385, on 10/12/2007, -15/+64The plane will take off.
Simple explanation:
Treadmill has no effect on the body of the plane
Physics style explanation:
Force exerted by treadmill => pure Rotational Kinematic Energy of the wheel
Force exerted by engine => pure Kinematic Energy of the plane.
More detailed answer:
The treadmill is acting tangent to the (assumed) free-spinning wheel. A force acting tangent to a free-spinning object can not cause any force on the axis, only a rotational force causing the object to spin about its axis. Therefor The only thing that the treadmill can do is cause the wheels to spin.
The engines on the other hand, are causing a thrusting force which is acting on the wings (or whichever part of the plan that the engine happens to be connected to. Since it is rigidly connected, the force is carried by the member it is connected with towards the CoM (Center of Mass). This transposed force on the Center of Mass causes an accelerations (F=ma). Basic physics principles will explain why and when a force can be translated to a different point. If you read and understand these principles you will note that the force can be translated from its origin to the CoM in a rigid body. Note, also, that on a free-spinning object, a force acting tangent to this object can not be translated to the axle which is the only part of the wheel assembly that is considered to be part of the rigid body of the plane.
Hence, if you use the basic theory of F=ma you will note that the sum of the forces acting on the rigid body of the plane is the thrust and only the thrust. Therefore, the thrust is directly proportional to the acceleration without regard to the force of the treadmill.
Now that was in a "perfect physical world." Very few things change when converting that logic to the real world. These are the following forces that should be taken into account:
Force of friction due to the wheel touching the ground: This can be assumed zero as the tire in both the stated question as well as in real life does not slip relative to the treadmill. If the tire did slip (as if it was locked up) the tire would be considered part of the rigid body and the force of the treadmill would effect the CoM and thus the acceleration. Whether the plane would be able to take off in such a situation would depend on the coefficient of friction between the locked wheel and the ground (very similar to how a seaplane is affected by the water it is in).
Force of friction due to rotation of the wheel about the axle: Most people would agree that a spinning wheel, especially if properly lubricated and fastened as it would be on a plane, causes very little friction on the axle. This friction, however, will add a force that is counteracting the thrust. Once again, though, for this force to cause a plane to not reach take-off speed, the wheel would have to have very high friction, and even then it would still depend on how powerful the engines are (once again, imagine a seaplane and the friction/drag caused by the water, yet it is still able to take off). Therefore, except in extreme rare cases, this will not substantially affect the motion of the plane.
Drag force: The plane is submitted to drag force caused by the air whether it is on a treadmill or not. Airplanes are built with aerodynamics in mind as to minimize this drag force. The only difference might be if the treadmill is causing a velocity in the air, however this would be similar to a breeze in the wind which would cause higher drag forces, but also would move more air over the wings causing higher lift forces. Therefore, in this problem this can also be assumed zero.
Hence, even in a non-perfect physical world, the plane still has a very overwhelming net force moving it forward.
A demonstration for the skeptical to prove that the plane moves:
Many people do not or can not understand the physics and believe the plane will still not move. To prove that the plane will move forward, try the following experiment.
Take a yo-yo (a free spinning one that will not automatically wind as it spins) and unwind the string. Now roll the yo-yo across the table by pulling the string. That is, in effect, how the plane would move on a normal runway: an external force not connected to the ground. Now, to make a moving runway, place the yo-yo on a piece of paper. While pulling the string in one direction, pull the paper in the opposite direction and note the results. It will move in the same direction that you are pulling. Also note that if you pull both slow, it may feel harder to pull than on regular ground. This is due to the rotational friction discussed earlier. However, if you increase the force with which you pull, you will also discover that the higher the "thrusting" force, the less of an effect the rotational friction has on the movement. To further this experiment, you can try replacing the normal string with fishing line to lower the friction even more, or by using ball bearings. Remember that a proper plane wheel will be greased and have relatively low friction.
A demonstration for those who do not understand the translation of forces:
Take a bicycle and turn it upside down to rest on the handle bars and seat. Next, take your hand and push on the front wheel at mid height of the wheel. you will notice that the wheel will not rotate and the bicycle frame may move. Now take the same wheel and push tangent to the wheel in any direction. You will notice that the closer you get to tangent, the more of your force that is turned into rotation and the less that is turned into a force on the frame. If you were able to push perfectly tangent (which is basically what the treadmill is doing) you will see that it has all of its force turned into the wheel spinning and none of it acting on the frame of the bicycle.
For those wondering my credentials: I am a senior in engineering at Penn State University, but 95% of this material was covered in my first two years of physics while in high school. The other 5% comes from the other 3 years of physics in college as well as the 3 years of Engineering Mechanics (that 5% being the non-perfect world scenario).
I hope that this clears up any misunderstandings about this problem, and if you made it this far in the post: congratulations. If you made it this far and still don't believe it will fly, go outside and play sports or find something else to do because you are too stubborn to learn physics.
To the creator of the meignorant: Stop spamming your digg as well as your website on forums such as www.techimo.com - seandaly, on 10/12/2007, -24/+73@Monolith2
Are you serious? I kept looking at your comment trying to find some sarcism in your response but alas, it is you that is the retard.
And those of you digging him up are just as retarded!
A planegenerates forward momentum with the "THRUST" of it's engines, wjereas a car generates forward momentum by applying force to spin the wheels, propelling the vehicle forward.
If you put a car on a treadmill and match the speeds, the car will go nowhere because the treadmill countering the wheels spinning would cancel out any forward momentum that would be gained. If you speed up the spinning wheels even .00000001% faster than the treadmill, the car would move forward, albiet very slowly.
Since a plane engines generates thrust whether it has wheels or not, one could assume that it wouldn't really matter how fast the treadmill was moving in the other direction, the body of the plane would not really be affected. (there would be a little bit of force applied by the treadmill, but it probably wouldn't be noticable to the pilot). As soon as the plane was moving fast enough where the air moving over the surface of the wings is providing enough lift, the plane will take off, regardless of how fast the wheels are spinning in the opposite direction.
Simple answer: Yes, the plane will most certainly take off, although someone should warn the pilot that he's on a treadmill! - falstaff, on 10/12/2007, -18/+62Since so many people are having a problem getting it:
A person or a car on a treadmill will remain stationary. An airplane on a treadmill, no matter how fast the treadmill moves, will move forward. The wheels of an airplane spin as fast as the airplane is moving through the air. If you put a treadmill under them, they'll move as fast as the plane through the air, PLUS the speed of the treadmill.
If you want to stop an airplane from taking off, you'd have to put it in a huge wind tunnel which is speed-matched to the thrust, to cancel it out.
Airplane is to wind tunnel as car is to dyno as person is to treadmill.
It's a trick question, people. You can't keep a plane stationary on a treadmill. - seandaly, on 10/12/2007, -10/+46@nsmike:
As strange as this sounds, you're incorrect.
It IS actually the air flowing OVER the wing, not just under it, that provides lift.
If you were correct, than you should be able to create a wing that was perfectly flat, angle it so that the front edge was a bit higher than the back, and it would provide lift. If that was the case, the ancient Egyptians would have flown thousands of years ago.
Wings are shaped so that when air travels across them, a low pressure zone is created above the wing, and a high pressure zone is created below the wing.
It's not just the force of the air pressure pushing up from the bottom of the wing. When you achieve a low pressure zone above the wing, you essentially create a vacuum. What happens when you hold a vacuum hose above a coin or some other object? It's lifted up.
We could go into more detail and talk about Laminar Flow, but that's another topic.
~s - lazycat, on 10/12/2007, -3/+38http://i83.photobucket.com/albums/j319/lazymalecat/Fly-NotFly.gif
- WarpFox, on 10/12/2007, -6/+40SOMEONE CALL THE MYTHBUSTERS
- cbasst, on 10/12/2007, -6/+35theoretically yes.
- togra, on 10/12/2007, -8/+35Ha, ha. So many stupid people making themselves look even more stupid by the arrogant way they make their incorrect assertions - Monolith, Spisska.
"There are four forces at work on a fixed-wing aircraft: Thrust, Lift, Drag, and g. When those forces are in balance, the plane does not move." - incorrect for a start - if the forces are in balance it means the plane does not experience any acceleration in any direction, not that it doesnt move.
Falstaff is right - whether the plane takes off or not depends on the relative motion of the plane against the air. The wheels on a plane are freewheeling. The engines of the plane will push it forward throught the air so the plane will generate lift, regardless of what the treadmill is doing. The treadmill does not exert a force on the aircraft (except maybe a slight increase in drag) as the wheels move freely. Therefore the plane will fly.
Anyone who wishes to argue against this is free to do so, but you are wrong. - IEatHamburgers, on 10/12/2007, -11/+37I'm sure your comments are completely valid and probably true, but there is no way in hell that I am going to read all of that.
- Lososaurus, on 10/12/2007, -3/+27Of course it will, dumbass. Why do you think aircraft carriers always turn INTO the wind? You get air moving over the wings, it's going to create lift, regardless of how that air is being moved. That was actually a problem with the 'flying pancake', the plane's self lifting body would generate so much lift that it create nearly enough lift to take off when it was just sitting on the deck of the carrier(or tarmac) with a solid headwind.
- polterbyte, on 10/12/2007, -2/+24If you search for "airplane" and "treadmill" in Google, you will, likewise, get several discussion threads with similar content. I babelfish'd some pages pointed by you, and the content is always the same:
First 5 to 10 posts: "No, it won't fly, because if it is standing still, the air will not flow under and over the wings, creating the necessary difference in pressure".
Next 5 to 10 posts: "You guys are wrong: the wheels aren't responsible for the movement of an airplane. It is not the wheels that propel it, but the force exerted on the air. The reaction to that force will propel the plane forward, no matter what surface it is standing on, and no matter if the surface is standing still or moving."
Remaining posts: Huge discussion ensuing from people who don't get Newton's Third Law against people desperately trying to pound sense into them.
Oh, and at least the first thread you pointed is just a regular forums, visited and maintained by regular folks, not by "best Russian professors". - zionKing, on 10/12/2007, -5/+26@monolith
"Are you guys ***** retarded? You need wind over the wings to fly, and putting the plane on a treadmill doesn't put wind over the wings.
Holy *****, you people should just shoot yourselves."
I stand by my original answer -- YES the plane flies. I bet you feel pretty cool now. I hear physics books are on sale at half.com. - allengeer, on 10/12/2007, -2/+22So a good way to think about this is think that you have a plane flying forwards at 100mph.
and right below it you have a treadmill going -100mph. Keep in mind the plane is flying, not on the treadmill. Given that the wheels are free to spin, when the plane touches down (with the equivalent engine thrust as when it was flying, and no breaks applied) on the -100mph treadmill what happens?
The wheels will spin backwards, but the plane will continue on past the treadmill, because the treadmill contributes no retarding force to the forward motion of the plane. The same goes for the plane as its trying to take off! And take off it will. - renzien, on 10/12/2007, -4/+24Here is a simple way to look at it, and I am so tempted to make use of my caps lock key for once...
We aren't talking about a car with wings (i.e. the engine is moving the wheels)
Without the treadmill it would lift then fall when it lost momentum, etc, etc, etc.
We are talking about a plane with engines on the wings.
It does not need the ground to gain momentum, nor do wheel rotations matter. - Lou3000, on 10/12/2007, -9/+28IT WILL TAKE OFF. Why are people digging up comments that say it won't, did you fail high school phsyics?
Yes, you need lift for a plane to take off the ground, but first the plane has to gain some airspeed. That is why we have runways.
Since you are thinking like children, think about it like this. When you play with your Hot Wheels in your room and you are pushing your cars around, what is making the car go forward. The wheels or your hand? It is your hand. You could spin the wheels as fast as possible, but if it is still in your hand then nothing is happening.
The engines on an airplane are doing the same thing, they are moving the plane regardless of what the wheels are doing. The wheels are simply there to hold the plane off the ground.
But yes, once it gets going fast enough it will have to generate lift, which it will do via airspeed. - pmuschi, on 10/12/2007, -2/+21@bemenaker
Don't think "ground speed", think "air speed". - polterbyte, on 10/12/2007, -2/+19That would be true if nobody on planet Earth knew any physics...
However, the contrary being the case, your "AFAIK" is only useful to quench thirst (provided it is ingested with two glasses of fresh water). - evolent, on 10/12/2007, -9/+26Yep. The wheels will be spinning twice as fast as they would if the treadmill was regular runway, but it'll take off just fine. There is subtlety to it though. I got confused for a bit and I'm supposed to know this stuff as a physics PhD student :)
If it were a car it wouldn't get anywhere, because a car pushes itself forwards by pushing back against the road with the wheels. If you stick a car on a treadmill which matches the wheel speed, then instead of pushing the car forwards, all you do is push the treadmill backward faster and faster, while staying in the same place.
The plane is not pushed forwards by the wheels. The only reason the wheels spin around is because there is a huge-ass force pushing the axle down the runway (from the engines) and then a tiny little frictional force pushing on the bottom of the tire (from the runway) which is just enough to make the wheels spin at the necessary speed.
All the moving treadmill does is to push back more on the bottom of the wheel then is normally the case. Twice as much, in fact, because it's moving backwards at the same speed the plane is moving forward.
It's all about where the plane gets the forward force from. It's kind of non-intuitive because we mostly experience the case like with cars, or like running on a treadmill in the gym, when we get the force from the friction with the ground. - Blazekun, on 10/12/2007, -4/+20In that case yes, but a treadmill doesn't move, nor does the air around it.
- feylanks, on 10/12/2007, -1/+17lazycat, demand your tuition back.
- polterbyte, on 10/12/2007, -3/+18@unabomber
"best Russian professors" of what? Home Economics?
If you have a link to those "struggles", please post it. - labbrat, on 10/12/2007, -4/+18Oh Christ, you are all going to be arguing over this for awhile...last time this was on digg it got >500 comments: http://digg.com/general_sciences/Physics_question:_Can_the_plane_take_off_
- inactive, on 10/12/2007, -2/+16Ok, this is quite simple and I'm surprised how stupid some of you people are. If this was a car then yes it wouldn't go anywhere, but this is an airplane.
As a plane's engines start to engage it is pushing the body of the plane forward over the ground, the wheels are essentially just there to keep the body off the ground and provide less friction. How much the wheels roll and what direction does not affect the direction of speed of the plane's forward movement because the wheels are just free spinning under the plane because the turbines of the jet are applying force directly to the body of the plane, not the wheels.
Imagine sitting next to an automatic treadmill with a skateboard. With the treadmill stopped and with just one hand on the skateboard you can easily move it back and forth. With the treadmill moving and one hand on it you can hold the skateboard still and also move it back and forth. No matter how fast the treadmill moves under the skateboard you can still move the skateboard forward and backwards. why? Because you are applying force to the body of the board and the wheels underneath are spinning unhindered. If you move it against the treadmill for that bit of movement forward the wheels are spinning slightly faster but the board still moves forward.
Same thing for planes, the turbines provide force directly to the body of the plane, just like your hand would provide force to the body of the skateboard. The speed at which the wheels turn has nothing to do with how fast the plane is going or how fast the plane has to go for take off. All the wheel's do is provide a low friction surface of contact for the plane against the ground. So even on a giant treadmill a plane can take off because no matter how fast the treadmill rolls the plane will be pushed forward by the body and the wheels will just spin faster underneath.
@xenofiend
I'd like to see this million miles an hour treadmill you are finding. It will never happen and the plane will take off. - dukeinlondon, on 10/12/2007, -2/+15heard about kites before ? They don't move, the air does and they fly.
- hfwarner3, on 10/12/2007, -1/+12African or European?
- falstaff, on 10/12/2007, -1/+12@bemenaker
"Lou3000, you are making an assumption of forward movement, the treadmill cancels all movement, the airframe sits still. Therefore no wind over the wings, no lift, no fly"
To continue the r/c car analogy:
Drive the car forward at 2 feet per second, then turn the treadmill on to 2 feet per second. It stays stationary.
Now, PUSH your car forward at 2 fps, with the treadmill set to 2 fps. The car is now moving forward at 2 fps *relative to the air* and 4 fps *relative to the treadmill*. The only way for it to stay stationary is for you to simply hold the car still. But if you give it *thrust*, it goes forward no matter what the treadmill is doing.
The difference is that when the car is driving itself, the thrust is acting on the wheels, but when you're pushing it, the thrust is acting on the frame. Airplane engines act on the frame, not the wheels. A small airplane engine will push the craft forward at a takeoff speed of 100 knots *relative to the air* but the craft will be moving at 200 knots *relative to the treadmill (runway)*. - deim, on 10/12/2007, -5/+16What's the problem with this "problem"?! Think of forces: you apply force from jet-engine (or propeller engine), it pushes plane by using stationary air as something to push from.
If you are saying that plane won't move, then where is this force from engine is spent to?! Friction from rolling wheels is about 0, so no force is wasted/applied here. Then where the engine force goes?!
It is primitive - regardless of any treadmill, plane WILL move and take-off, unless the plane is moving by powering the wheels :-) but in this case plane will not fly - there is no ground to roll on high in the air :-) - Otto, on 10/12/2007, -2/+11The water is actually able to exert force on the plane. The treadmill is not, unless the pilot hits the brakes and locks the motion of the wheels.
- jstevewhite, on 10/12/2007, -3/+12Run on a treadmill with a paper airplane - then THROW it. Wow, look at that! Thrust that's NOT RELATED to the movement of my feet - just like the jet engines produce thrust unrelated to the rotational velocity of their tires.
And then the dude with the pig comment agrees with you, and *and then gives a good example of why you are wrong.".... holy crap. - mod4l, on 10/12/2007, -4/+13Oh lord, this is getting so silly.
1. The engines will push the plane forward, whether it is standing on a treadmill, sheet of ice, or any other smooth surface. The wheels are a PASSIVE component- unless they are locked, they will not transmit any significant amount of force back to the plane! Unless the bearings in the wheels burn out and the wheel snaps off, you're moving!
2. Because the plane *moves*, it will be moving faster than the surrounding air, and it will therefore fly.
Everybody who thinks the plane is sitting still has to re-examine point #1 until they "get" it. When the treadmill moves to "match the plane's speed", all it is doing is making the wheels spin twice as fast! The plane itself really doesn't care unless the bearings burn out. - gizmo490, on 10/12/2007, -1/+9@bmorrow and GTPilot
Even without physics you should be able to see that your argument ends up creating a paradox. First off for the plane to not fly it needs to not go forward ie stay stationary. If the plane is staying stationary then the treadmill is not moving as it is matching the speed of the plane. If the treadmill is not moving the the plane would obviously go forward because of the force of the thrust on the plane. Now that the plane is moving the treadmill must be moving at equal speed and so the plane must also be stopped. Doesn't make a lot of sense does it?
The only way the plane wouldn't take off is if the horizontal component of frictional force created by the wheels spinning against their bearings on the landing gear of the plane was equal to that of the thrust provided by the engines. For this to happen the wheels would have to be spinning so fast that they would fail as if I remember correctly frictional force drops off exponentially with increase in velocity. (I may be wrong it may actually be a polynomial function of degree at least 2 I can't remember enough about the equations we got for this in our lectures) - Otto, on 10/12/2007, -4/+12>>>"The amount of energy required to take off will roughly double..."
No, it won't. It will be ever so slightly higher because there's a slightly higher amount of friction due to the faster speed of the wheels, but that amount is very small by comparison to the rest of the energy required for taking off.
The pilot will probably not notice any major difference in taking off at all. - noahhoward, on 10/12/2007, -0/+8Mr. Prussel you must be a rocket scientist.
/sarcasm/ - t0ny, on 10/12/2007, -5/+13So... I'm confused. As long as the wings have air flowing over them they will generate lift.
The way it sounds is that the plane is going against the the motion of the plane. So the wheels are going twice the speed of the plane. As long as they dont explode it should work.
Just for those of you that dont know there is NO motors in the wheels. - Pilot85, on 10/12/2007, -1/+9OK. Let's remove the engine from the equation entirely. You and a bunch of buddies tie a rope to the engine mount on a wheeled airplane. This plane happens to be sitting on a giant treadmill. You and your buddies take this rope and pull. The treadmill matches the speed of the wheels perfectly (please read WHEELS and not PLANE). You however, are unaffected by the force of the treadmill as you are standing in front, and not on top of it. You begin to pull on the rope as hard as you can. Will the plane move forward? Yes! Because just like the airplane engine/prop/thrusting force, you are not affected by the rotation of the treadmill. The WHEELS will spin very fast, yes, but the PLANE will still move forward.
- m0bitz, on 10/12/2007, -0/+7If you happen to read this before you post...don't. Whatever your argument is, it is futile. You will come to believe half of the people here are just plain stupid, relative to your point of view. You will weep for the future.
Participation in this thread will consume you.
You have been warned. - Otto, on 10/12/2007, -1/+8>>>"If I were to walk around said airplane and put my hand on one of the wings, what would I feel?"
A very brief pain, as you were sucked into the engine of an airplane going past you at 500 MPH.
The treadmill does not make the plane stand still. It cannot possibly do so. - inactive, on 10/12/2007, -1/+8@bemenaker
But the treadmill is not some magic wall that will stop a plane, the plane will move forward, its simple logical physics. The plane will move and a treadmill can't move fast enough to stop it. - zzz1357, on 10/12/2007, -2/+9I don't want to be offensive, but by now it should be *pretty clear* the plane will fly.
- Rabbethan, on 10/12/2007, -4/+11What does putting it on a treadmill do? The wheels don't move the plane, they just get pulled along with the plane, which is pulled with the engines, not the wheels.
- kuj007, on 10/12/2007, -2/+9@jasonprussell
your combination of self-righteousness and complete ignorance makes my head hurt so bad I can barely stand it. - EntropyMan, on 10/12/2007, -0/+7The plane probably needs both wings to fly.
- Otto, on 10/12/2007, -10/+17>>>"As a pilot..."
As a pilot, you should know that the wheels turn freely when you don't have the brakes applied, right? So if the plane is on a treadmill, and you let off the brakes, and fire up the engine, what happens?
Answer: You move off the treadmill. The wheels will spin freely. The engine does not make the wheels turn, it pushes the actual *plane* through the air.
Come on, man, this is simple physics. Any pilot should know this instinctively. - xiphoris, on 10/12/2007, -0/+7@baugles:
NO. How are you so stupid? Jesus christ man. When YOU are running on a treadmill, you get your forward force from the GROUND.
AN AIRPLANE GETS ITS FORWARD MOMENTUM FROM THE AIR. The airplane can of course begin moving, because it is PUSHING AGAINST THE AIR. Treadmills only keep things stationary that push against the ground. - Otto, on 10/12/2007, -1/+8The fact that the treadmill matches the speed of the plane makes no difference in the motion of the plane. The treadmill cannot move the plane backwards. Why? Because the wheels turn freely.
Okay, yes, if the plane was not applying thrust, then the friction on the wheels would be enough to move the plane. However, once those wheels are spinning and the plane is moving, the only thing turning the treadmill will do is make the wheels turn faster.
That treadmill, no matter how magical it is, cannot spin fast enough to increase the friction high enough to equal or overcome the thrust produced by the jet engines on the plane. Even a prop plane has more thrust than that.
So the plane moves forward. The treadmill, since it acts on the wheels, cannot stop the plane from moving forward. -
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