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"Plane and a Treadmill" Problem Explained by a Canadian watch!

meignorant.com — A plane equipped with fixed horizontal engines and wheel landing gear is placed on a huge treadmill runway. The treadmill has a clever design and always matches the speed of the plane, but runs in the opposite direction. Will the plane take off and fly or not?

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lazycat 1 year 163 days ago , made popular 1 year 162 days ago

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kuznetsoff, on 10/12/2007, -64/+9Ne vzletit.
For NonRus - It's imossible!
- polterbyte, on 10/12/2007, -77/+27Of course the plane will never take off!
  
  Actually, that's exactly why hovercrafts aren't able to move, and rockets aren't able to take off from Earth or move in space. ;)
- NICU, on 10/12/2007, -74/+6Does anyone have an RC plane and a treadmill? I'm sure with some trying you can find a way to recreate this.
  
  Maybe if you can get an RC plane with some very smooth tires and try to make that take off on very smooth ice it could be similar... As long as you can get the plane to not move horizontally.
- zionKing, on 10/12/2007, -78/+55Instead of a treadmill, imagine the same plane sitting on an iced-over runway. The icy runway is as flat as a mirror... and perfectly slick. You can't even walk on it. The air is perfectly still relative to the ground. When the engines fired on... would the plane move forward? Your answer to this question and to the "Plane and a Treadmill" question should be the same ("yes").
  - grovest4life, on 02/23/2008, -0/+1why is this Dugg down it is true
- Monolith2, on 10/12/2007, -174/+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.
- echo1, on 10/12/2007, -58/+20yeah seriously i thought the same thing as soon as i saw this, i dont understand how it's a "problem". it's just not possible.
- 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.
- WorldGroove, on 10/12/2007, -50/+44@Monolith2
  Actually, this plane & treadmill thing was posted to Digg a long time ago. It fooled me for a full hour, but eventually... you'll realise that the plane will still take off. Why? Because the friction between the wheels and the ground has nothing to do with how a plane generates force to move forward; thus lift off.
- WarpFox, on 10/12/2007, -37/+4He's cute.
  
  Math is stupid.
- Monolith2, on 10/12/2007, -78/+41@ WorldGroove
  
  You dont get it, though. You need air moving over the wings to fly. Running on a treadmill doesn't push wind over the wings, thus there's no lift and no way for the plane to take off.
  
  Even putting that aside, and assuming that somehow the plane magically takes off, there would be no way for it to stay aloft, since it has no momentum and would immediately stall out and crash.
- adml_shake, on 10/12/2007, -45/+4A lot of you seem to be forgetting that it's a 2 stage system for that plane to take off. The first one being that the wheels are the means by which the energy gets the plane moving fast enough to put lift on the wings which is stages 2. While it's true that the wheels themself don't generate the forward momentum that is where it's applied to. If you cancel that fact then the plane just sits there. Like a car on a dyno.
- Monolith2, on 10/12/2007, -43/+4...
- WorldGroove, on 10/12/2007, -24/+4@Monolith2
  EDIT: Nevermind, You figured it out. ThumbsUp.
- klaymen, on 10/12/2007, -21/+12no one is claiming the plane will take off stationary. thing of what is pushing it forward. it's not the wheels. it's like if a toy car was on a treadmill, and you pushed it forward and the treadmill tried to keep up. eventually the plane will start going forward fast enough to lift off.
- PhrosTT, on 10/12/2007, -36/+10Zionking: "Instead of a treadmill, imagine the same plane sitting on an iced-over runway. The icy runway is as flat as a mirror... and perfectly slick. You can't even walk on it. The air is perfectly still relative to the ground. When the engines fired on... would the plane move forward? Your answer to this question and to the "Plane and a Treadmill" question should be the same ("yes")."
  
  WTF are you talking about? If the plane can slide along the ground with zero friction than the engines will suck in air and generate thrust to accelerate forwards and eventually take off.
  
  A plane on a treadmill is ***** retarded. No air will be moving over the wings since the plane is not moving relative to the stationary air. Without any volume of air moving over the wing, no ***** lift, and no ***** takeoff. How is this even a serious question?
- Jonny5alive, on 10/12/2007, -9/+6http://www.duggmirror.com
- feylanks, on 10/12/2007, -33/+116monolith2 - 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.
- defe007, on 10/12/2007, -18/+16The plane should take off. Think about it this way. Say you have a rocket with wheels and you place it on the same treadmill, you say the rocket won't move forward right? What happens if you take the wheels off the rocket? The rocket will move forward. I think the same concept applies to the plane.
- Otto, on 10/12/2007, -8/+99>>>"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.
- matthewaaron, on 10/12/2007, -14/+5Leave it to a Canadian...
- NSMike, on 10/12/2007, -36/+15@Monolith -
  
  Actually, lift works by getting more air UNDER the wings than over. That's why the wings are angled upwards to the direction of movement. If you look at a formula 1 race car, you'll see the wings on that are pointed downward to the direction of movement. This pushes the car down and generates more friction. More friction gets better grip on the road. So, air OVER the wings is exactly the opposite of what you want.
  
  And in actuality, you can perform this test yourself. Just take a skateboard and put it on a treadmill and perform a number of experiments. First, put it on the treadmill and turn it on without touching it. Assuming the treadmill is not angled, it'll stay in place on the belt and be dumped off. Then, take the skateboard and hold it in place with your hand. You'll see that the wheels move, but the board itself stays in place. Now, push with your hand in whatever direction you want it to go. Suddenly, the board moves, and the wheels move faster or slower, depending on whatever direction you push it. Now, in the case of the jet, the treadmill itself will sense the increase in force the engines create and compensate by moving faster, thereby keeping the jet in place. Since we know that jets don't spontaneously take off when their engines are running at full power, but that they take off when sufficient lift is created, sitting in one place because of the compensation of the treadmill will keep the amount of air moving under the wing from accumulating sufficiently to create enough lift to make the plane take off.
- DisposableRob, on 10/12/2007, -14/+8"and putting the plane on a treadmill doesn't put wind over the wings."
  
  No, but the prop engine on the front or the jet engine at the rear does. We're talking about a plane, not a glider.
- seandaly, on 10/12/2007, -24/+72@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!
- 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_
- mt066, on 10/12/2007, -2/+54It's hilarious how much this is ***** everyone off.
- seandaly, on 10/12/2007, -10/+45@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
- spisska, on 10/12/2007, -25/+12Come on people. Use your bloody heads.
  
  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.
  
  When thrust is greater than drag, the plane moves forward. Forward motion moves air over the airfoils which creates a pressure differential and generates lift. When lift is greater than g, the plane rises. What matters as far as lift goes is the plane's speed relative to the air, not the ground.
  
  A plane on a treadmill is generating thrust, but the treadmill is generating an equal amount of drag -- i.e. the wheels may be moving but the plane is not. If there is no air moving over the airfoils creating a pressure differential, there is no lift. Period.
  
  Similarly, if you point an aircraft directly into a 60-knot headwind, the plane will generate lift and (assuming a rotation and/or stall speed of less than 60 knots) will take off, regardless of whether or not it is generating thrust.
  
  This is why airplanes always take off and land in the same direction, and it is always into the wind, which generates more lift at lower groundspeeds.
  
  This is also why pilots use a number of different measurements for speed: groundspeed (speed of plane relative to the ground), indicated airspeed (the speed indicated by instrumentation), true airspeed (indicated airspeed adjusted for wind conditions and direction), etc.
  
  Imagine a small plane with a stall speed of 60 knots flying at 80 knots indicated in a 50-knot tailwind. The groundspeed is actually 130 knots. If the indicated airspeed drops below 60 knots, the plane will stall (i.e. there will be insufficient air moving over the airfoils for lift to exceed g, leading the plane to drop like a rock even though it still has a groundspeed of some 100 knots (50 knot tailwind + 50 knot indicated airspeed).
- falstaff, on 10/12/2007, -18/+61Since 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.
- bemenaker, on 10/12/2007, -30/+6A propeller does not push enough air over the wings to create lift for flight. A propeller does one thing and one thing only, it provides thrust. You need that thrust to move the body (wings) of the airplane forward to generate lift.
  
  This plane will not launch, because it has zero ground speed, therefore, zero wind over the wings to generate lift. Without the airframe having forward velocity, you get no lift from the wings.
  
  And whoever said you don't want air going over the wing, you don't understand how a wing works. You have to have air going over and under a wing to get lift. The wind on top has to travel a further distance than the wing on bottom, this means it travels faster, which lowers the pressure. The higher pressure from the slower wind under the wing is were you get the lift from. Your analogy to a car is almost correct, except cars are naturally shaped like a wing, that is why the wings you see on race cars, are inverted. The curve is on the bottom, to push down, instead of up.
- GTPilot, on 10/12/2007, -20/+4the plane's weight is on the wheels until the airspeed is enough to produce lift.
  
  sure thrust comes from the prop or turbine and not the wheels, but how does it get from 0 to take-off speed?
  
  unless the plane can accellerate from 0 to take-off airspeed faster than the treadmill could accellerate (which is not the hypothetical situation here), then the plane is staying on the ground.
  
  if you say the plane can take-off in this situation, then you are basically saying a plane with gear up, sitting on its belly, could take off without scratching the hull.
- pmuschi, on 10/12/2007, -2/+21@bemenaker
  
  Don't think "ground speed", think "air speed".
- 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.
- 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, *****.
  
  "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.
- 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.
- WarpFox, on 10/12/2007, -6/+40SOMEONE CALL THE MYTHBUSTERS
- Kbennett, on 10/12/2007, -11/+4Oh, for **** sake. Air must pass both under and over a wing to create lift. Lift is created when faster moving air passes over a wing and slower moving air passes under it. The force applied by slower moving air is greater than that of faster moving air and therefor lift is generated.
- 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 :-)
- WarpFox, on 10/12/2007, -11/+4THRUST VECTORING OWNS THE SKY
- 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.
- 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.
- bemenaker, on 10/12/2007, -15/+2I got dug down, because I put the wrong term? What I meant was aiframe speed through the air, which is air speed, you are correct. That withstand, the rest of my post is accurate.
  
  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.
- xenofiend, on 10/12/2007, -14/+11 gizmo490 - said:
  "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)"
  
  Exactly. If the treadmill matches the speed of the plane then it will go as fast as it needs to to overcome the forward momentum of the aircraft. The only thing that will stop the plane from moving forward will be the friction of the bearings. even if the treadmill hss to spin a million miles an hour; whatever it takes for the friction of the bearings to prevent the plane from gaining any forward momentum thus preventing takeoff. As gizmo said, the wheels will probably fail due to heat, but that plane sure as hell wouldn't be taking off.
  fools.
- vandread, 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.
- togra, on 10/12/2007, -1/+7Benemaker, you are still wrong. Please try and read the arguments of those who are explaining. As the question is stated, the treadmill does not cancel out the forward motion of the aircraft relative to the air - which is what generates lift.
  
  "The treadmill has a clever design and always matches the speed of the plane, but runs in the opposite direction"
  
  This does not cancel out the forward motion of the plane, as the wheels are freewheeling, the motion of the plane through the air is (mostly) independent of the treadmill and is governed by the thrust of the engines.
- vandread, 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.
- 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)*.
- DaveV, on 10/12/2007, -1/+4@*****:
  "A plane on a treadmill is generating thrust, but the treadmill is generating an equal amount of drag -- i.e. the wheels may be moving but the plane is not. If there is no air moving over the airfoils creating a pressure differential, there is no lift. Period."
  
  BZZZZZ! Wrong answer!
  
  The treadmill does not provide any drag. It convers thrust from the motion of wheels on it into the motion of the belt on the treadmill. The wheels on an airplane provide no thrust so there is no transfer of energy from the wheels to the treadmill.
  
  The thrust of the airplane comes from moving air (prop or jet). The thrust of a sailboat or landsail comes from moving air (wind). To better understand what is happening, image a landsail ( http://www.landsail.net/ ) on a treadmill. Will the landsail move? Yes. because the landsail is being pushed by the wind. Now imagin an airplane on a treadmill. Will the airplane move? Yes, because it is being pushed jet exhaust or pulled by the props. The wheels are just there to keep the airplane off the ground and lower the friction between the airplane and the ground.
  
  The lift for an airplane comes from the flow of air over its wings. The flow of air is caused by the plane moving through the air. Even if the plane is on a treadmill, it will still move because the thrust comes from the props or jets, not the wheels, so it is like have a giant hand pushing or pulling the airplane.
- umdigger, on 10/12/2007, -4/+3@seandaly
  
  You are somewhat correct, a wing is given its shape for the purpose of creating lift on one side or the other. There are wings that are perfectly symmetric on each upper and lower side that create lift with a positive alpha, check out your NACA airfoils.
  
  BUT you can have a perfectly flat wing that will create lift if it has a positive angle of attack. The key here is turbulence (which would quickly appear in a 'flat' wing). By creating a turbulent vortex on the upper side, it creates a low pressure area, which in turn creates lift. Granted there is a very thin line between it creating lift and stalling. But that line is in fact there.
  
  So don't be too quick to dismiss someone elses comment because you don't think it is correct.
  
  ....did someone say the Kutta Condition?
  
  So my assessment of this question: No matter how fast the wheels are moving, it is the relative air around the wings that causes a plane to fly. If the body is stationary relative to the air around it, it will not fly.
- charlescheese, on 10/12/2007, -12/+1Actually, the plane would crash. Once it started moving forward, it wouldn't have enough thrust to be airborn once leaving the treadmill, it's landing gear would hit the concrete, collapse, and everyone would DIE. :)
- FJR1300, on 10/12/2007, -4/+2 xenofiend said..."The only thing that will stop the plane from moving forward will be the friction of the bearings. even if the treadmill hss to spin a million miles an hour;"
  ....Here is a given... the treadmill is super sized... it's infinitely long and can go infinitely fast.
  In order for the treadmill to speed up, it must measure an increase in wheel speed. The only force that can increase the wheel speed is the horizontal thrust of the jet engine. So, increase the thrust, the wheel speed increases... but wait! If the wheel speed increased, doesn't that mean that the plane had to move forward, even just a little bit? Yes! So, for every increase in thrust, the plane moves forward. So, the treadmill just increased in speed to match the wheels, but the plane moved forward just a bit! Get it? Now start stacking thrust increases, and all those little movements start to stack up. The faster you increase the thrust, the faster the plane will be moving. Thrust up fast enough, and the plane will have enough forward movement that it will lift off.
  The speed control for the treadmill does not run the treadmill faster than the wheels, it just matches the wheels. If an external for acts upon the plane to move it forward (thrust), the speed controller will increase the treadmill speed accordingly, but it does NOT make the plane back up to it's original position.
- gizmo490, on 10/12/2007, -2/+5@ xenofiend
  "Exactly. If the treadmill matches the speed of the plane then it will go as fast as it needs to to overcome the forward momentum of the aircraft."
  
  If the treadmill matches the speed of the plane then it will go as fast as the plane is moving. NOT fast enough to counteract the force from the thrust of "forward momentum". The treadmill moving at the negative velocity of the plane would not provide the frictional force on the bearings and landing gear from rotation of the wheels to counteract the forward thrust from the engines. Since the system would then have a positive force in the direction the engines are pushing the plane would accelerate and take off.
  
  The case where the treadmill moves fast enough to counteract the force from the engines via friction on the wheels is different from the one where it moves with the negative velocity of the plane.
- Zippo, on 10/12/2007, -3/+2This guy needs to make more videos, he's hilarious.
  And what province is he from? I want to shake his hand.
- Kbennett, on 10/12/2007, -4/+1Wrong spot. Nevermind.
- GliTCH82, on 10/12/2007, -10/+1THE REAL EXPLANATION:
  
  I don't think a lot of you people understand what the hell is going on. If you put a plane on a treadmill and cut the engines and make the treadmill run backwards at 180 mph, the plane will move backwards right? So let's say you turn the engines on at like .01%. What you're saying is the treadmill should have no effect and the plane will start moving forwards as though the treadmill doesn't even exist?
  
  Now put the engines at 80%. Newton says that the effect of the jet pushing on the air back behind the plane will propel it forward, and if you match the treadmill and engine thrust properly the plane will appear to be standing still. But it won't FLY, because in order for there to be a takeoff, the WIND has to move over its WINGS. Just because engine thrust is propelling a plane forwards, doesn't mean there will be wind over the wings if there is a treadmill moving backwards to counteract that force.
- bbhh, on 10/12/2007, -2/+5i can't believe how people don't understand that it will take off. okay either do this, or imagine it. grab a toy airplane, push the landing gear down, turn on your moms treadmill as slow as it goes, put the plane down but hold onto the wings, and push it against the flow of the treadmill, then after a foot or two pick it up. wow you flew, congratulations. now turn the treadmill up as fast as it goes, and do the same thing, move the plane at the same speed against the flow of the treadmill (see how it isn't any harder?) and then pick it up. wow you flew, congratulations. in this illustration: your hand is the jet engine(s). the wheels spin as fast as they have to, they don't matter.
- GliTCH82, on 10/12/2007, -4/+3"the treadmill doesn't detract from the ***** jet turbines or props pulling or pushing the plane through the air."
  
  Of course it does. If the engines were off and the treadmill moving backwards, the plane would move backwards. Turn the engines on to generate the same force the treadmill is exerting on the plane and the plane will appear to be standing still.
- xenofiend, on 10/12/2007, -0/+2@FJR1300
  
  Granted. I assumed the the treadmill was trying to reduce the airspeed of the plane to 0. Instead, as you pointed out it matches the speed of the plane. However if the plane's wheels were not able to handle ground speeds of 2X takeoff speed, they would break before the plane got off the ground. I suppose most aircraft wheels are rated for more than double the takeoff speed, but that wasn't specified. BTW, I am just playing devils advocate here, but thanks for pointing out my logic error.
- GliTCH82, on 10/12/2007, -2/+3"Friction from rolling wheels is about 0, so no force is wasted/applied here. Then where the engine force goes?! "
  
  Why do you assume there's no friction? Are you saying if I put a shopping cart on a treadmill and don't push it, it will stay there and not move anywhere? There's definitely a coefficient of static friction the plane will have to overcome from the weight of the plane being exerted on the treadmill, regardless of whether there are wheels there or not.
- DaveV, on 10/12/2007, -1/+0@GliTCH82:
  
  The plane would roll backwards due to inertia. The motion if the airplane is not a function of the speed of it's wheels. The speed of it's wheels is a function of the speed of the surface the wheels are contacting and the speed of the plane.
  
  Because the forward motion of the plane is generated by the engines moving air, and not by the wheels spinning against the "ground", if the airplane generates the force necessary to go say 10mph, and the treadmill is powered and goes 10mph in the opposite direction, the effect is to cause the wheels on the plane to go 20mph because the wheels spin freely.
- GliTCH82, on 10/12/2007, -4/+2I have an addendum to make to my posts up above.
  
  I thought about the problem a little more and I realized that the above only applies if the friction was static all the time. Of course once the plane starts rolling from the force of the engines, the friction is going to decrease dramatically, but there will still be friction.
  
  I guess the way I visualized the problem is that the treadmill could be powerful enough, and the wheels could be strong enough, for the treadmill to counteract the kinetic friction introduced into the equation by the wheels bearings, etc. After all, if this were a REAL WORLD problem, there is no treadmill big enough or powerful enough to exert a counter-acting force on 2 jet engines.
  
  I guess my point is, in this hypothetical scenario that you are all pondering, if the wheels were strong enough and the treadmill was fast enough you could generate enough friction on the ground to counter-act the force from the engines, and the plane would NOT FLY.
- nickconsumtion, on 10/12/2007, -2/+5"It's a trick question, people. You can't keep a plane stationary on a treadmill."
  
  This is the most important comment in the thread. I think most everyone here actually agrees with each other, but continue to argue because some see the trick and others don't.
  
  When I first heard the question, my immediate response was, "of course it won't fly, there's no lift since the plane won't be moving fast enough relative to the air." That is still true. If one somehow held a plane still (i.e., with some kind of tether that could withstand the thrust) while the engines are at full throttle, then release, the plane won't immediately take off.
  
  But as others have pointed out, a treadmill won't keep the plane stationary. No matter how fast the treadmill spins, the plane will begin moving forward. Eventually, assuming the treadmill is long enough or there's a runway at the end of it, the plane will pick up enough speed to lift off.
- GliTCH82, on 10/12/2007, -4/+1What makes this problem so hard to visualize is the lack of an apparent limitation to the treadmill's power. If you say, for example, that the treadmill could only spin up to 1000 mph, then the plane would have no trouble countering that force because it's only being exerted on the wheels. The plane's engines could easily overcome this, and if the wheels were strong enough, the plane would eventually take off and fly.
  
  However since there is no limit to the treadmill's power or the wheels' strength, as mentioned above, you could theoretically spin the treadmill at thousands or hundreds of thousands of miles per hour (hypothetically) and generate enough kinetic frictional force on the wheel bearings to counteract the engines, and the plane WOULD stand still.
- DaveV, on 10/12/2007, -1/+5@GliTCH82:
  
  The one thing one must remember is that the forward speed of the aircraft is not a function of its wheels. The forward speed of an aircraft, on the ground or in the air is a function of the thrust generated by it's engines. The engines generate thrust by moving air, they do not generate thrust by contact to the ground.
  
  Believe it or not the treadmill is irrelevent. Even if one assumes that the treadmill is infinately long and capable of infinitate speed, the limiting factor is the ablity of the wheels to hold together. If the wheels will hold together at twice takeoff speed, then the airplane will become airborn.
- Otto, on 10/12/2007, -1/+6For all you people saying that the treadmill can go as fast as needed to stop the plane... If the treadmill can go infinitely fast, then the treadmill must have frictionless wheels inside it, otherwise it would have a finite top end to its speed.
  
  If the treadmill can have zero-friction wheels, then so can the plane. At which point, your argument still falls flat.
  
  No matter which way you slice it, the plane *must* move and thus take off. Period.
- GliTCH82, on 10/12/2007, -4/+2"For all you people saying that the treadmill can go as fast as needed to stop the plane... If the treadmill can go infinitely fast, then the treadmill must have frictionless wheels inside it, otherwise it would have a finite top end to its speed."
  
  No one is saying the treadmill can go infinitely fast. All you would need to do is figure out how fast the wheels would have to spin to create enough friction to counter-act the engines, and then design a treadmill fast enough to create that force.
  
  The point is, there IS a speed at which the treadmill could spin at, theoretically, that would exert enough force to keep the plane at an apparent standstill.
- Otto, on 10/12/2007, -0/+2>>>"No one is saying the treadmill can go infinitely fast. All you would need to do is figure out how fast the wheels would have to spin to create enough friction to counter-act the engines, and then design a treadmill fast enough to create that force."
  
  Unfortunately for you, rolling friction doesn't take speed into consideration, it only considers weight and resistance coefficent.
  
  You cannot have enough speed in your treadmill to overcome the engines, ever.
  
  See http://en.wikipedia.org/wiki/Rolling_resistance for more.
- GliTCH82, on 10/12/2007, -3/+2"Unfortunately for you, rolling friction doesn't take speed into consideration, it only considers weight and resistance coefficent."
  
  Friction on the wheel axis, however, would make a difference. And the faster the treadmill, the higher that resistance. A treadmill fast enough would create enough resistance on the wheels to keep the plane grounded.
- tfinniga, on 10/12/2007, -0/+1
  
  The plane will move.
  
  If the plane didn't move, there would be no lift, as air wouldn't be pushing past the wings, pressure difference, etc.
  But the plane will move, because the plane pushes against air to get speed, not against the treadmill.
  
  Lets assume that you had a car with wings on it, but no propeller. It's trying to push against a treadmill that's rolling perfectly away. The car will be stationary, the wings will have no lift, the car won't fly.
  
  But an airplane pushes against air, so the treadmill doesn't really matter. Instead, let's imagine that what the plane is pushing against is moving opposite to it, in the same way as the magic treadmill does for the car. This would be a magic wind tunnel. A fan blows air towards the plane at the same speed that the propellers on the plane blows it backwards. This would be analogous to the car with the treadmill. The only difference is that because wind is blowing by the wings, there is lift.
  
  I was going to say something about a submarine with wheels on a treadmill, but you can probably figure it out.
- bdrydyk, on 10/12/2007, -0/+2So, I'm a bit late, but I just have to know.
  
  Are digg users digging monolith up as a joke?
- savmac, on 10/12/2007, -0/+2You all are so stupid! There's no such thing as a treadmill big enough for a plane to go on... duh!
- MannyHills, on 10/12/2007, -0/+2From reading this later, Monolith2's first incorrect post is still dugg way up, which is still unfortunate. However, after that it seems that pretty much all the correct answers are now dugg up. So I'm glad the digg community finally found the right answer.
- carve, on 10/12/2007, -0/+3This is supposed to be a website for technically minded people, yet most of you don't seem to be getting it. If you had a plane on a treadmill runway, it would be just like a regular runway with the following minor exceptions...
  
  1) Nose-wheel steering would be a bit more sensitive
  2) The engines would have to work just a little tiny bit harder to overcome the extra friction in the wheel bearings, since they're spinning faster. Very little...maybe 1% harder
  
  As long as you don't exceed the structural limits of the landing gear & tire, and you have a long enough runway- errr..."treadmill", ground speed is irrelevent- airspeed is what you need to take off. e.g., if you need an airspeed of 60 knots to take off, and you have a 20 knot headwind, then your groundspeed will be a mere 40 knots at takeoff. If you have a 20 knot tailwind, ground speed will have to be 80 knots. The point is that it doesn't really matter what your ground speed is, and all a treadmill would do is increase your apparant ground speed as though you had a tailwind- The airplane will not remain fixed on one point over the treadmill- it will move forward along the belt. If you don't believe me, start jogging on a treadmill and then have a 'friend' apply some thrust be shoving you in the back. Did your airspeed increase? You betcha.
  
  -Carve
  P.S. - I'm a Mechanical Engineer in the aerospace industry and have been to test pilot school
- carve, on 10/12/2007, -1/+3Let me put the treadmill question in terms you all can understand.
  
  Q: When you are in an airplane, and it takes off, the wheels will (eventually) stop spinning, right? When that happens, does the plane fall out of the sky? Why or why not?
  
  A: No- the plane keeps flying because airpseed is not necessarily affected by apparant groundspeed.
- Gdoubleod, on 10/12/2007, -0/+1All that ranting and raving and he didn't even bother to answer the question (at least in any comprehensible way)... that is why arguing on the internet is like the special Olympics even if you win you're still retarded...
  
  The way I see the problem is this.
  The force to move the plane forward is not done by the wheels it is done by the thrust of the jet engine. Therefore the plane will still move forward. If you would like to try an experiment to prove this get a toy car (preferably a hot wheels Ferrari) and put it on a treadmill then hold the car in place... look the wheels are moving as fast as the treadmill and the car is not moving at all. Then flick the car with your free hand in the butt and the car will move along the treadmill... and the wheels won't spin any faster than the treadmill..
lazycat, on 10/12/2007, -19/+8Imagine it's a seaplane. Try taking off against an increasing current of water!
- polterbyte, on 10/12/2007, -18/+10It would still take off. Newton's third law guarantees it. In both cases, the plane pushes the air, and not the treadmill/water. The air--as a reaction--pushes the plane. In both cases the plane flies.
- cbasst, on 10/12/2007, -13/+9This is different than in the treadmill scenario because the water is pushing back on the plain, rendering it uncapable of achieving a speed at which can provide enough lift to overcome the gravitational forces enacted by the earth upon the plane.
  
  Picture it as if there was no friction on the ground. Air friction is still there. Would the plane still take off? This is more similar to the treadmill experiment.
- 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.
- bmorrow, on 10/12/2007, -12/+2The Frictionless argument is wrong. The Treadmill will not Reduce Friction it will increase Friction holding the plane in place. If the Treadmill maintains the same speed as the plane then Friction=absolute. If the Friction is absolute then there will be no lift.
- aliengoods, on 10/12/2007, -9/+3@bmorrow
  
  A plane can take off with absolute friction in relation to the ground. If the air flowing through the engines caused enough airflow over the wings, then you would have lift. The ground isn't a concern. Now it would take a hell of an engine to generate that kind of airflow over the wings of a stationary plane, but it would take a hell of a treadmill to create absolute friction.
- GTPilot, on 10/12/2007, -5/+3@aliengoods
  
  you would be correct if your airplane had a take-off speed of 0. even a small cessna requires airspeed of around 55 mph to take-off.
- 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)
- GTPilot, on 10/12/2007, -7/+1@gizmo490
  
  you fail to consider gravity. if the plane were weightless, then your 'freewheeling' theory would be correct.
  
  the plane uses the friction against the ground to move forward until it acheives take-off speed.
  
  you are basically saying that a plane sitting on its belly (gear upon the runway) could take-off without scratching it's hull.
  
  gravity.
- Otto, on 10/12/2007, -0/+6>>>"the plane uses the friction against the ground to move forward until it acheives take-off speed."
  
  No, it most certainly does *not*.
  
  The plane moves due to Newton's third law. Air or jet exhaust is blown out the back of the engine/prop. The plane MUST move the other way.
  
  The plane moves because it is pushing against the air. It never, ever, pushes against the ground, under any circumstances.
- GTPilot, on 10/12/2007, -7/+2otto :) .. you are forgetting newton's law of gravity. thrust doesn't oppose lift, it opposes drag.
  
  lift opposes weight.
  
  you need to have positive lift before you are airborne.
  
  in a world without gravity, or when dealing with vertical take-off aircraft, you would be correct.
- BuckCynnie, on 10/12/2007, -0/+4@ GTpilot:
  
  "in a world without gravity, or when dealing with vertical take-off aircraft, you would be correct."
  
  In a world without physics, you would be correct.
- Otto, on 10/12/2007, -0/+1>>>"you need to have positive lift before you are airborne."
  
  True. Your lift is generated by the wings moving through the air at high speeds, thanks to all that thrust you have. You move, you get positive lift, you take off. Simple, really.
kuznetsoff, on 10/12/2007, -17/+4*****
nahuy, on 10/12/2007, -14/+2Sure it wont takeoff, the gear would prevent it from moving.
unabomber, on 10/12/2007, -10/+1I bet it will.
- kuznetsoff, on 10/12/2007, -9/+1I rate 10$.
lazycat, on 10/12/2007, -3/+38http://i83.photobucket.com/albums/j319/lazymalecat/Fly-NotFly.gif
unabomber, on 10/12/2007, -41/+2AFAIK no-one can prove or disprove this :)
Kinda ***** conversation ; )
- 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).
- unabomber, on 10/12/2007, -36/+1FYI, best Russian professors struggled against this puzzle and as far as we know it - there's no definite solution for the time being.
- 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.
- kooft, on 10/12/2007, -10/+11This isn't a serious discussion is it? Please tell me it isn't. Because there's already a 'magical' runway that matches the speed of an aircrafts tires. All you have to do is hit the brakes and voila, matching speeds. Then, just simply apply max power to the engines and wait...
- noahhoward, on 10/12/2007, -7/+12Applying the brakes drastically changes the situation.
unabomber, on 10/12/2007, -19/+0@polterbyte
I do have but all discussions are in Russian unfortunately ;(
Professors of physics, of course, I remember 100+ forum pages where aviation students along with their professors tried to find the truth, unsuccessfully...
Here's the link - if you understand a bit of Russian then you may find out how many web pages are dedicated to the problem of "vzletit/ne vzletit".
http://www.google.com.ua/search?hl=uk&q=%D0%B2%D0%B7%D0%BB%D0%B5%D1%82%D0%B8%D1%82+%D0%B8%D0%BB%D0%B8+%D0%BD%D0%B5+%D0%B2%D0%B7%D0%BB%D0%B5%D1%82%D0%B8%D1%82&btnG=%D0%9F%D0%BE%D1%88%D1%83%D0%BA+%D1%83+Google&meta=
- 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".
- evolent, on 10/12/2007, -4/+2A thread in English:
  http://boards.straightdope.com/sdmb/showthread.php?t=348452
lazycat, on 10/12/2007, -48/+3So.. if an aircraft career is doing like 200 knots than a plane on it's deck will take off without any acceleration! %rolls:eyes%
- cbasst, on 10/12/2007, -6/+35theoretically yes.
- Blazekun, on 10/12/2007, -4/+20In that case yes, but a treadmill doesn't move, nor does the air around it.
- 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.
- dukeinlondon, on 10/12/2007, -2/+15heard about kites before ? They don't move, the air does and they fly.
- feylanks, on 10/12/2007, -1/+17lazycat, demand your tuition back.
- noahhoward, on 10/12/2007, -0/+4I remember reading a story about that... somewhere. I think the Doolittle bombers managed to take off on that principal btu I remember reading or hearing about some aircraft that wasn't really meant to be on an aircraft carrier but was for one reason or another (it had ditched or something like that) it needed a certain amount of airspeed that the carrier was able to generate by steaming into the wind. The aircraft just lifted up and the pilot drifted off to the side.
- bemenaker, on 10/12/2007, -0/+2Nowhard, they didn't just lift up and float off the side, well maybe totally empty w/o much gas, but fully loaded, that was the only way they could launch. The carriers were running at Flank speed into the wind. That gave them about 40-50 knots of wind speed bonus to lift off with.
- noahhoward, on 10/12/2007, -0/+1Oh, yeah I know the bombers didn't. The other story was some plane that only needed a very low airspeed to lift off.
TIMODetritus, on 10/12/2007, -17/+24Of course the plane will fly... it will take off like the treadmill isn't even there. In fact, if the pilot couldn't see the treadmill he wouldn't even know he was on one. The force acting on the plane making it move forward is independent of the wheels/treadmill it is an outside force. The plane pushes on the air and in turn the air pushes on the plane, all that would happen is that the wheels would spin really really fast.
- 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.
- diatrevolo, on 10/12/2007, -19/+2"always matches the speed of the plane"
  
  READ people. Of course it won't take off, just as a plane without wheels won't take off. It doesn't propel by its wheels, but does require them to move and catch enough wind. WILL NOT TAKE OFF. Return your mail-order diplomas.
- diatrevolo, on 10/12/2007, -10/+3...OR WILL IT?!?!?!?!?
- tfinniga, on 10/12/2007, -0/+1Okay, here's another completely hypothetical situation:
  
  A submarine equipped with fixed horizontal propellers and (for some totally unknown reason) wheels is placed on a huge underwater treadmill. The treadmill has a clever design and always matches the speed of the submarine, but runs in the opposite direction. Will the submarine move forward or not?
  
  The submarine will move forward, but those wheels are going to spin. However, it doesn't matter, as the wheels don't affect the speed of the submarine, they just spin. Sure, theoretically, you could run the treadmill fast enough to get friction on the bearings of the wheels sufficient to counteract the force of the propeller. However, that would be a heck of a lot faster than the speed of the submarine, so it wouldn't be a match, as specified in the question.
  
  Now let's transfer that over to the airplane on a treadmill. Both have propellers that exert force on the fluid that surrounds them - water for the sub, air for the plane. Both have wheels on a treadmill. The only difference between the situations is that air is invisible and less viscous, so it's harder to think about as a fluid that could exert force.
  
  But the airplane will move. And if the airplane is moving, air is flowing above and below the wings at different speeds: lift.
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
- 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.
- jasonprussell, on 10/12/2007, -37/+9@butch81385
  
  If I were you, I'd ask Penn State for my money back.
  
  Too bad your engineering studies haven't taught you one simple thing. How to read the problem. The problem is that no matter how fast the plane goes, the treadmill is counteracting that forward motion. Without forward motion, that plane is not going to fly due to insufficient lift. Now, if we had the same treadmill problem, but had a nice headwind (say 80-90 knots for a small plane), the plane would be able to take off due to sufficient lift. As a pilot, I can attest myself that if I'm sitting on the tarmac with my brakes applied and with full throttle on the engines, the plane will just sit there. The treadmill has no effect on lift. To everyone who thinks the plane will fly after reading the original problem, please educate yourself (not at Penn State) first before opening your mouth.
- 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.
- BuckCynnie, on 10/12/2007, -4/+9The best explanation so far. I was going to say the same thing, but I didn't know what it was I was going to say until I read your post. :D
  
  I am always amused with people who wouldn't take a moment to read a science mag, much less book, but feel they are qualified to chime in on a question based on principles they no nothing about.
  
  And folks, don't mistake qualified for entitled. Everyone is entitle to an opinion, but not everyone is qualified to give it.
- brandiniman, on 10/12/2007, -2/+5@jasonprussell
  So if I took the space shuttle and went full throttle on a treadmill I'd go nowhere? C'mon. The engines do no push air over the wings people... look at some airplane designs and you can see some engines can be completely separated from the wing yet accomplish the same thing. Engines push the aircraft through the air which THEN creates lift as the air moves over the wing.
  
  The only force applied to the plane from the treadmill is a little friction (much like holing a matchbox car on a treadmill). If you put a bottle rocket on the car it it'd move forward, and if you then added wings, it'd take off. The thrust is pushing the air not the ground.
- count_z, on 10/12/2007, -5/+5@diatrevolo
  @jasonprussel
  
  Why do you people insist on proving how much you don't know? I don't understand why this is so hard to understand: the wheels don't matter. It's been explained sooooo many times yet don't even try to understand what people are saying so you revel in your ignorance.
  
  Take a VSTOL airplane (like the Harrier Jump Jet). You have ever seen one take off? It's thrusters push downward, then when it has enough height, they push forward (like a normal) plane... and *gasp* it moves forward.
  
  There's no ground to push against (as its several feet in the air), yet somehow it "magically" still manages to move forward. What does this prove? That the ground and the wheels don't matter.
  
  Since the thurst isn't generated by the wheels, it won't be affected by the threadmill (just like a rocket... when it's... um... rocket fires, it moves the damned thing because of the force that it is generation against). Once there's enough thrust, the plane WILL move forward (like the Harrier which isn't even touching the ground).
  
  Think of a missle: The trust from its rocket moves it forward. Put one on a wheels on a threadmill and it will STILL move forward.
- 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.
- noahhoward, on 10/12/2007, -2/+5Prussell if I ever hear your name in relation to an airplane crash I'm going to go ahead and call in the 'pilot error' tip to the FAA. Or would you like us to tell them you encountered a treadmill?
  
  Oh, and Butch, sorry you had to take the time to explain all that and still met with ignorance.
- clickwir, on 10/12/2007, -4/+5@jasonprussell
  
  Doesn't really matter if you are a pilot or not. The plane would take off just fine.
  
  Try this... take a toy plane and put it on a treadmill. Turn the treadmill on, the plane will fall off the back. Simple.
  
  As a pilot, you know that the planes engines push off the air, they move air, not ground. The engine is not hooked to the wheels. Now you cant really put some engines on the toy plane, but we can simulate the force. Your hand. Simply reach out and push the plane forward. It moves forward. Now try it with the treadmill on. Can you push the little toy plane forware? Of course you can. The treadmill moving in the other direction makes the wheels spin faster, but does NOT stop you from pushing the toy plane forward.
  
  Same thing on a big plane.
  
  The engines push off the air, not the ground. Thus the plane will fly just fine.
  
  I know, I saw a video of someone with a remote control plane on an actual treadmill. It took off.
- AgentMull, on 10/12/2007, -2/+2You basically summed up everything I wanted to say while reading everyones comments. Some people just dont understand how our world works.
- ewok85, on 10/12/2007, -1/+5God I hate this question, I look at it and go "nah, it won't create lift because air will not pass over the wings because it will not move forward", then I remember, "duh, the wheels do not add any force to the body of the plane, they"ll spin like mad but it still wont stop the airframe from moving forward".
- lauerk, on 10/12/2007, -0/+2Ok, just think about it.
  
  The plane will only be completely stationary at the beginning, since the treadmill only goes in the opposite direction when the plane is moving forward and achieved non-zero speed. Speed of an aircraft is determined by the its motion relative to the air mass surrounding it, not the wheels. The problem indicates the treadmill is keeping up with the speed of the aircraft, not its wheels.
  
  It would not be like the pilot was holding the brakes. So say it's a Cessna 152 and rotate speed is at 55 knots indicated airspeed. The treadmill would be going the opposite direction equally, with the only result being the wheels would be spinning twice as fast. With the wings going through the air at 55 knots, the C152 would takeoff.
- PieHeaven, on 10/12/2007, -9/+2The answer is simple, and it doesn't take a physics phd. It is the lift on the wings. If the plane is not moving, there is no lift on the wings, and thus no reason for the plane to take off.
  
  Please explain how an aircraft could rotate without lift on the wings.
  
  MS Aeronautical Engineering, University of Dayton.
  Licensed Pilot
  Licensed Aircraft Mechanic
  Writer of software that simulates aircraft
- kuj007, on 10/12/2007, -2/+6@PieHeaven
  
  IANAE, but I do have a freakin' brain and I don't write software that simulates airplanes (and it sounds like neither should you)
  
  All the problem says is that the treadmill runs counter to the speed of the plane, it *doesn't* say that the plane is stationary... the implication that everyone gets caught on is that the treadmill could somehow prevent the plane from moving and thusly creating lift (like you point out). But the treadmill won't prevent that if the wheels are freely moving.
- count_z, on 10/12/2007, -1/+3@PieHeaven
  
  If your credentials are accurate, then I'll just have to assume that you aren't thinking about the problem.
  
  As you should know, the engines generate thrust. The wheels don't have motors, so they only start to move when the thrust generated is greater than the weight of the plane multiplied by the coefficient of friction (i.e. the force that resists movement) between the wheels and the ground (we'll call it Force X)... there's also air resistance, but it isn't significant at low speeds.
  
  If the plane is on a threadmill it will only remain stationary as the long as the thrust is equal to force X, however no matter how fast the threadmill is spinning, force X remains a constant. So when the trusters produce more force than Force X (which is the only thing that affects the wheels), the plane will start to move.
  
  Rockets move just fine without having wheels or touching the ground. VSTOL planes move forward just fine even though they had no forward movement once they were in the air.
  
  Stop thinking about cars and things that provide their power through their wheels.
- bemenaker, on 10/12/2007, -5/+1Where are you getting forward speed of the airframe? The treadmill counteracts and forward thrust generated by the engine. Therefore there is a net speed of zero. Yes, the wheels will spin, but as the plane moves forward, the treadmill is speeding up. You are making an assumption the plane is driving the treadmill. The problem does not state that, the problem states taht treadmill is independent of the plane and that it matches the speed of the plane. Therefore, there is net gain of zero speed on the airframe.
  
  If the plane were responsible for spinning the treadmill, you would be correct.
- PieHeaven, on 10/12/2007, -3/+4@everyone
  
  I see so clearly now......It was a trick question. Since that is the case, no one should have argued anything. The question should read "could a plane move forward even if it is on a treadmill."
  
  However, the clear intention of the questioner is that the wheels have enough friction to
  prevent sliding on the conveyor belt. Therefore the plane is not
  decoupled from the belt's motion. And in the scenario described, will
  not be able to take off.
- Otto, on 10/12/2007, -1/+2>>>"However, the clear intention of the questioner..."
  
  The clear intention of the question was to trick you into thinking that the treadmill could counter the forward motion of the plane, when it cannot possibly do so. The question is designed to make you think a plane is like a car, where the wheels spin to push the car forward. But we know that's not true, don't we?
  
  The plane moves, and flies.
- zeeeej, on 10/12/2007, -1/+6I'm begging the "pilots" to stop posting on this one. I have to fly on Friday...
- doc.oliver, on 10/12/2007, -0/+2If we start by making the assumption that this planes ability to lift is directly related to the amount of air that passes over (and under) the wing we should ask ourselves how this phenomenon happens under normal circumstances (removing the treadmill from the equation).
  
  The (obvious) answer is that getting wind passing over (and under) the wing is achieved either by accelerating the wind around the wing (put it in a wind tunnel) or by generating forward motion (of the wing). Assuming we are not in a wind tunnel we conclude that the simplest solution is to get the wing (which is attached to the plane) moving forward in relation to the wind; thereby creating lift.
  
  So how is this forward motion created? Well, either we have a force pushing the plane forward (by pushing something backwards); or we have one that pulls the plane forward. The assumption made is that the plane generates its own force by the "push" method simply because it's the least ex centric one.
  
  But what are we pushing from? It has to be something that is constantly available during normal flight, so "push ground by force of spinning wheel" won't fly (pun intended); so instead we turn to air. The engine (jet or propeller) pushes of the air behind it and thereby creates an equal (and opposite) force that thrusts the plane forward.
  
  If we now add the treadmill back into the equation (in the off position); but we place the plane a few centimeters above the surface of it; will it have any effect on the thrust provided by the engine? What about if we turn the treadmill on; or even if we put it in reverse? Nope, no effect (OK, there is a small effect since there is friction between the moving surface and the air around it, but unless you think that an effective fan looks just like a treadmill we can disregard that).
  
  So now we go back to the original example by putting the wheels of the plane to the moving surface of the treadmill. The forward motion of the plane is not (significantly) affected by the speed (or direction) of the treadmill no matter what speed it runs at; it only affects the speed of which the wheels of the plane are turning.
  
  So the plane moves forward no matter what speed or direction the surface under it moves at ergo it takes of (when sufficient airspeed is achieved). The main idea with the question is to confuse the reader by insinuating (or rather right out saying) it's possible to get the plane to stand still by adjusting the speed of the treadmill.
  
  PS. butch81385 has one of the best and most professional explanations I've seen but I still wanted to put in my 2 cents.
- count_z, on 10/12/2007, -0/+1@PieHeaven
  
  The wheels could never have enough friction to impede the forward motion of the plane, it's not possible. The jet engines provide tens of thousands of pounds of thrust.
- count_z, on 10/12/2007, -0/+1@PieHeaven
  
  As an addendum, even if the wheels, somehow, magically could provide enough resistance, they'd be ripped from the fusilage (again: tens of thousands of pounds of thrust).
  
  In either case, the plane would go off the threadmill. There's no way around it.
- GliTCH82, on 10/12/2007, -2/+2"Believe it or not the treadmill is irrelevent."
  
  The treadmill is NOT irrelevant because it's exerting frictional force on the wheel bearings and tires.
  
  Without a treadmill that force is NOTHING and the engines overcome it and the plane takes off. But if the treadmill had unlimited power and the wheels were strong enough, the treadmill could spin fast enough at hundreds of thousands or dare I say millions of miles per hour to create enough friction on the wheels to counteract the thrust of the engines.
- GliTCH82, on 10/12/2007, -2/+2"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."
  
  Once again, I reiterate, that this force COULD be high enough to counteract thrust if the treadmill were spinning fast enough. Since the problem as stated in the description does not limit the treadmill's speed, and you and I both agree that there obviously is a level of friction, no matter how high, that can be reached to counteract that thrust, then there IS a theoretical speed at which the treadmill could run to counteract the thrust of the engines and keep the plane from taking off.
- count_z, on 10/12/2007, -0/+0@GliTCH82
  
  The question stated that the threadmill would match the speed of the plane. If you change it to allow the speed of the threadmill to go to an infinite speed (and it would have be moving many, many, many times faster than the plane to generate enough friction) and make the wheels and the fusilage infinately strong, you're change the problem and the question:
  
  You're asking if an infinate force could stop the plane from moving. And the answer is: duh.
  
  If the threadmill is matching the speed of the plane, there wouldn't be enough friction and the plane would take off.
- PsychoticCarp, on 10/12/2007, -0/+1A lot of you are misunderstanding the question, the treadmill can only go backwards as fast as it goes forward, this is not enough force to prevent the plane from moving forward, the question itself tells you the plane will fly.
  
  for the treadmill to go backwards 1 mph then the plane MUST be moving forward at 1MPH, for the treadmill to be moving backwards 300MPH the plane MUST be moving forward at 300MPH which is enough speed for a plane to lift. At that point the wheels would be moving at 600MPH
lazycat, on 10/12/2007, -11/+2BTW what does the Canadian say?
- zionKing, on 10/12/2007, -1/+2he never says it outright but he argues for the plane taking off...
- r00t3r, on 10/12/2007, -2/+6Eh?
- zionKing, on 10/12/2007, -0/+1the "Feel my brain" Canadian in the video doesn't make it clear what his *conclusion* is, he just illustrates the *logic* and principles of physics he followed toward his conclusion. However if you listen to his whole argument and read the comments, the guy concludes that the plane will take off.
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.
synmoo, on 10/12/2007, -6/+12The plane will take off... period. Like others have said, the wheels will be spinning faster than normal, but the plane will take off as if nothing were out of the ordinary . The plane does not push itself with the wheels. If it did, then it would not take off.
Tbab, on 10/12/2007, -7/+10How is it that people still do not understand this problem? It's so simple, it embarrasses me to think that there are other people who don't get it.
- noahhoward, on 10/12/2007, -4/+8Spare yourself the superiority complex this is designed specifically to make you think. It is meant to confuse people. The first thought for most people is that equal but opposite forces cancel each other out. It takes a minute (and some knowledge of dynamics) to get around that and realise that the force cancellation occurs between the ground and wheels leaving the thrust free to do its job.
- mod4l, on 10/12/2007, -2/+1People have a natural difficulty to abandon their "intuition" and re-calibrate. That's one reason some interviewers use those outrageous "microsoft-style" questions. That said, this is something you can train, but to do it, you really want an authoratative source, and the internet isn't a great place for that. In this case, the problem really is pretty straightforward (planes push off of the AIR, not the GROUND!), but ask your local physics teacher or professor if you really don't think so.
- gizmo490, on 10/12/2007, -1/+2@mod4l
  I don't get why people think intuitively that the plane will not take off though. I immediately thought that the treadmill wouldn't matter without thinking about the dynamics involved. I really wish some one would explain the "plane would not fly" aspect of this problem better as I just don't get where they are coming from.
- Philodox, on 10/12/2007, -1/+1@Tbab I'd get off your high horse.
  
  I'm a reasonably intelligent person but when I first saw the problem I figured the plane wouldn't take off because I was thinking about the problem as though the plane were a car or a jogger. It took a bit of reading and abstraction of the problem to get to the right answer.
- GliTCH82, on 10/12/2007, -1/+1The problem appears to be so simple to you, but because I'm taking into account friction on the wheel axis I believe that there is most definitely a speed the treadmill could run at which would generate enough friction to keep the plane on the ground. It would be ridiculously high, but then again this whole problem is ridiculous in the first place.
NanoStuff, on 10/12/2007, -15/+2Every time this question is presented, on every forum in every corner of the world, it splits friends and families, kills little kittens and makes the world that much more awful.

But yes the plane will take off. The amount of energy required to take off will roughly double, but assuming that's not a limitation, they plane takes off. K? K.
- 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.
- NanoStuff, on 10/12/2007, -6/+1Wrong you are my friend. If the belt were moving at twice the speed, the aircraft would be incapable of taking off as the wheels would not be able to advance on the belt. The belt would in effect be moving backwards at the rotational speed of the wheels leaving the plane stationary. Reducing that speed by half effectively halves the load on the plane.
  
  No, I don't expect you to believe me :)
- Otto, on 10/12/2007, -0/+3>>>"If the belt were moving at twice the speed, the aircraft would be incapable of taking off as the wheels would not be able to advance on the belt."
  
  Sorry, but no.
  
  A car moves by making the wheels spin. This applies a force between the wheels and the ground, and that force makes the car move along the ground.
  
  But a plane doesn't have a motor on the wheels. It moves by pushing the body of the plane itself against the air, with a jet or a propeller. The wheels spin freely. They can roll either way, it doesn't make any difference which way they roll, because they're just hanging from the plane itself, which is pushing against AIR.
  
  The treadmill can spin all it likes, it's the plane pushing against the air that causes the plane to move. And that will happen no matter what is happening to the wheels.
- GliTCH82, on 10/12/2007, -1/+1"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."
  
  So, can we agree that the treadmill spinning faster would increase that small amount?
dsmx, on 10/12/2007, -18/+1The plane takes off because the planes engines force air over and under the wings, thus the plane does take off however due to the fact it will not be moving forward when it takes off it will tend to drop as it starts to move forward due to it being below stall speed and likely it will crash.
- Otto, on 10/12/2007, -5/+10>>>"...due to the fact it will not be moving forward..."
  
  No, it will move forward just fine. The treadmill does not prevent the plane from moving. See Newton's Third Law.
- kryx, on 10/12/2007, -2/+3@dsmx
  
  That is just plain wrong...
- Domdogg123, on 10/12/2007, -0/+1@dsmx: Please explain to me how the engines force air over the wings when the plane isn't moving?
speezer, on 10/12/2007, -3/+5It's more fun to think about a plane on a treadmill on earth which is tilted on it's axis and spinning around at 25000 miles per day as it goes around the sun at about 67000 miles per hour and all that moving around the galaxy and drifting through the universe. Yes, the plane takes off. It can land too if the treadmill is long enough.
LiberalAK, on 10/12/2007, -20/+11I can't believe how stupid some of you people are!!!

The worst offenders are the totally ignorant morons out there like Monolith2:
"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."

Well Monolith... if you had even the most BASIC understanding of things, you would realize that OF COURSE the plane will take off you stupid fool!

The planes wheels spin free, they provide no thrust. Don't you know how airplanes work??? GOOD GOD YOU ARE DUMB!!!

This is like a brain teaser for 8th grade science class, and even then the smarter kids in the class would be like "Oh come one this is soo easy, of course the plane will take off."

Seriously, you people need to take a hard look in the mirror and ask yourself... "Where did I go wrong that I am so stupid, and so sure I am right when clearly I am a freaking retard."

If I were you, I would think about going back and finishing high school, or if you actually managed to graduate, I would sign up for some GED courses to remind yourself of all that stuff you thought you learned.

But on the other hand... I guess it's people like you that vote Republican, so thanks for that.
- noahhoward, on 10/12/2007, -4/+5Calm down, you're showing yourself to be an ass. You can cut the generalisations as well; there are a lot of people who voted republican who know a damn site more than you (if it's just me then by all means continue using the generalisation). In any case, political orientation has nothing to do with this issue.
- PecanHead, on 10/12/2007, -7/+4> But on the other hand... I guess it's people like you that vote Republican, so thanks for that.
  
  Uh... wow... Somehow you managed to bring politics into this discussion? Thanks jerkoff - it's people like you that are ruining this country with partisanship.
- jstevewhite, on 10/12/2007, -7/+9@noahhoward
  
  It's not STRICTLY true that politics is completely unrelated... as IQ (and education) increase, the probability an individual is a 'liberal' goes up in direct proportion. :D No, that doesn't mean all smart people are liberals, just that MORE smart people are liberals.
  
  Waiting as I get dugg down... :)
- noahhoward, on 10/12/2007, -0/+3That may be true but It doesn't really matter much when you're talking about generating lift.
- clickwir, on 10/12/2007, -3/+2@stinkbutt
  
  You have no idea. It's extremely hard. Constantly having to explain things over and over. Dumb things down.
  
  I might sound like an egotistical ass hat, but dumb people really do hold everyone back. Even other dumb people. No, we are not all equal.
- RyanistheRyan, on 10/12/2007, -7/+1riguiscott is right. and you are one of those ignorant fools.
  air does need to be moving, faster above the wing and slower beneanth the wing. moving (faster) air has less pressure then non moving (slower) air. pressure always move from areas of more pressures to areas of less, to attemp to become balanced so to say.
  if it is on a treadmill, sayin that the wheels are spinning, but it(the plane) is not moving, there for, no air is moving, how could it take off? what would produce that force that it soo needs to fly?
  thats why we use WIND TUNNELS, to demontrate flight, not a treadmill. windtunnel would provide the moving air needed to produce lift.
  you are a disgrace to democrats, and you represent the republicans we all hate. i think you fall almost into the stupid conservative area, based on your attitude.
  some side effects of this flight though, jus for the curious of though;
  engines would possibly overheat-depending on plane
  the plane(well actually the treadmill, the plane wouldnt be moving at all, the whole conumdrum.) could actually hit the speed that it would fly at, on the ground. which means, anything behind it, would be pretty much blown away by the engines, but not by the moving air over the wings.
  if someone can use a real theory and explain how it would relate to it being able to lift without moving air across the wings, then please, go ahead n explain.
  as for the possibility of have props in the front, which are in front of the wings(on small twin engine aircrafts), i do not believe they generate enough lift over the small amount of wing they cover, but if they did, at the high speed(still not movin technically) theyd hit on the treadmill, it might produce a weak but enough lift to make it fly. it would need a considerably higher groundspeed then if you did it without a treadmill, if it even is possible.
  must i say, pwnd?
- fantasticFlan, on 10/12/2007, -0/+2"I can't believe how stupid some of you people are!!!"
  
  Welcome to the world. Sorry I missed the birth yesterday, I trust your mother is recovering well.
- Domdogg123, on 10/12/2007, -0/+1@ryanistheryan:
  
  What you fail to realize is that the forward speed of the plane is related to the backward speed of the treadmill.
  
  So for the treadmill to be moving 50mph, the plane must be moving 50mph. And when I say the plane is moving 50mph, I mean that the plane is *MOVING*, not the wheels of the plane turning, and pushing it forward.
  
  Since the force of the treadmill is not linked at all to the force of the plane, it moves forward, and by moving forward creates lift, which enables it to take off.
mbabauer, on 10/12/2007, -16/+10I don't think this would take off. The plane is traveling fast, relative to the surface its traveling on (the rubber treadmill), but the wings are traveling 0mph against the part that provides lift (air). Unless the air is moving over the wing, the wheels can turn as fast as they want, but the plane will sit.
Alchemeron, on 10/12/2007, -15/+8It will not take off because, by being stationary, it will never build up the required airspeed.
greenzer0, on 10/12/2007, -15/+8Are you people serious?

Run on a treadmill while holding a paper airplane. Let me know what happens when you drop it.
- Rabbethan, on 10/12/2007, -3/+9Does this paper airplane have engines pulling it?
- jasonprussell, on 10/12/2007, -9/+4@greenzer0,
  
  Very good example, although I'm sure the slower people will ask about the engines.
  
  Sure, I suppose if you had enough thrust (a rocket for example) and you crossed your fingers, the plane could take off.
  
  But... If I strapped wings to a pig and put a rocket up its ass and threw it out of an airplane it would fly too.
- noahhoward, on 10/12/2007, -0/+8Mr. Prussel you must be a rocket scientist.
  
  /sarcasm/
- 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.
- apeweek, on 10/12/2007, -0/+1If the paper airplane had a little rubber band propeller, and you let go if it, would it move forward? Of course it would, just like it would if you were sitting in a chair instead.
  
  Now put wheels on it. Of course that would not matter. If you made the wheels touch the treadmill, why would that stop it from moving?
- greenzer0, on 10/12/2007, -1/+2Throwing it would be the exact example that would prove it would fly. Thanks for finishing and clearing up my post guys.
nme1337, on 10/12/2007, -5/+7Summary for the slow people:

Yes it will fly, but only if it is being propelled by its engine. No it will not fly by a treadmill just spinning its wheels.

The acceleration of the plane has NOTHING to do with the wheels (see float plane) The reason the plane moves foward is because its pushing air. (Same way a boat moves in the water). The fact that a treadmill is moving the wheels has no bearing on the movement of the plane. The wheels will spin as fast as the plane is moving + as fast as the treadmill is moving.
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.
- Wireddd, on 10/12/2007, -3/+6it doesn't do anything of course. the treadmill is just to trip up those that are a little slow.
- GliTCH82, on 10/12/2007, -1/+1Actually, for those of us that are slow

"Plane and a Treadmill" Problem Explained by a Canadian watch!