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  1. #1
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    Plane on a Treadmill

    As we're all internet forum addicts... I'm sure we've heard of the "Plane on a Treadmill" puzzle.
    And just to summarize - the question is, if a plane is on an infinitely long treadmill that is capable of accelerating to match the speed of the plane, will the plane take off?

    There's no official answer, and you can find die hard supporters of both answers.

    Well, Mythbusters is taking it on. They actually originally planned to air it a month or so ago, but delayed it. If I'm correct, it's airing this upcoming Wednesday - the 30th.

    Perhaps everyone would be interested in placing bets for takes off vs. doesn't take off. Moderators would have to be in control of what wins, theoretically the Mythbuster result. But they've had controversial results in the past, and could end up with a "possible" or "unknown" result, etc. So we'd have to let our moderators choose winner or tie/no result.

    Anyone remember if this (plane on a treadmill) has been discussed here before?



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    Re: CyBookie - Plane on a Treadmill

    as a quick addition -- part of the debate is what exactly does the puzzle mean. Mostly on what is implied by the treadmill's ability. Generally I think it's accepted that the treadmill will match the plane's wheel's acceleration and velocity. So as the wheels start to go, the treadmill begins to go the other direction.
    (hopefully this helps clarify for those new to the question)



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    Re: CyBookie - Plane on a Treadmill

    It will still take off.



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    Re: CyBookie - Plane on a Treadmill

    im not an engineer or a physicist. the classes i took in either discipline are not enough to even merit an educated guess.... in fact i studied social science so excuse any of my ignorance.

    however i was under the impression that air pressure above and below the wings is what caused lift. if the propulsion is negated by the treadmill and the wings are unable to actually cut through the air and create an air pressure differential how can lift be created?



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    Re: CyBookie - Plane on a Treadmill

    Its a dumb question because the thrust is generated by the turbines not by an axle spinning the wheels, and with the turbines spinning it will create the pressure change and thus you have lift

    PS I'm a Fine Arts major, it doesn't take a genius to figure this out.


    Last edited by Aaron Jacobs; 01-26-2008 at 03:00 AM.

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    Re: CyBookie - Plane on a Treadmill

    are you serious? Im an ME and this is a dumb question.



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    Re: CyBookie - Plane on a Treadmill

    I'm staying out of this, all I'll say is the wheel speed does not mean a thing. How fast the wings are splitting the air is what counts. In other words how fast the plane is moving relative to the ground (not the treadmill). As the air splits the wing the particle on top moves faster (greater distance to travel) than the particles on the bottom thus creating lift.



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    Re: CyBookie - Plane on a Treadmill

    So MythBusters got a Big Treadmill, huh?

    I agree, it will not take off, but what do I know.



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    Re: CyBookie - Plane on a Treadmill

    Where are the aeronautic engineers? I know there are a couple on this board and I am sure this question got brought up in school.... and i'm sure they know the answer.


    Now that MBB is back, do we still have to pretend that WBB matters?

    -acgclone

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    Re: CyBookie - Plane on a Treadmill

    And for the record I would put a LARGE sum of money on the plane taking off.


    Now that MBB is back, do we still have to pretend that WBB matters?

    -acgclone

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    Re: CyBookie - Plane on a Treadmill

    Lift is created by the air on the top of the wing moving faster than air going below the wing (low pressure on top of the wing vs. high pressure below it). If you were to place the plane on a treadmill you're not moving any air over the wings. Just think of yourself running on one, do you feel a breeze the faster you run?? No, so the plane would definitely NOT take off...



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    Re: CyBookie - Plane on a Treadmill

    It will not take off....case closed. ME grad with Thermodynamics classes taken.



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    Re: CyBookie - Plane on a Treadmill

    Exactly how does the conveyor belt keep the plane's speed in check? The wheels are free to move - the conveyor belt can speed up as much as it wants, but the plane still has forward thrust from the prop/turbine.


    Now that MBB is back, do we still have to pretend that WBB matters?

    -acgclone

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    Re: CyBookie - Plane on a Treadmill

    The speed of the "runway", or treadmill in this case, is irrelavent. The plane is pushed forward by the thrust from the engines, not the wheels, the wheels basically spin freely. I don't know if Mythbusters will be able to prove this or not with their tests, but I would bet money that the plane will take off under the right conditions of a test.

    If a plane was landing on a treadmill that was matching it's speed exactly would it just come to a hault as soon as it hit the ground? No.


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    Re: CyBookie - Plane on a Treadmill

    Quote Originally Posted by JRCampy View Post
    Lift is created by the air on the top of the wing moving faster than air going below the wing (low pressure on top of the wing vs. high pressure below it). If you were to place the plane on a treadmill you're not moving any air over the wings. Just think of yourself running on one, do you feel a breeze the faster you run?? No, so the plane would definitely NOT take off...
    This summarizes best without using engineering language. Lift is created as the difference in speed relative to the air and the wing. If the air doesn't move, the plane doesn't move. The difficulty in this excercise is keeping the treadmill pace equal to the plane's attempt at acceleration.

    Another way to look at it is that it is easier to take-off against the wind rather than with the wind. Accordingly, if the turbines are not allowed to propel the edges of the wing because the turbine force is negated by the rotation of the wheels against the treadmill, it is a no go. Again the trick will be to match the treadmill and plane acceleration.


    Last edited by IsUaClone2; 01-26-2008 at 09:34 AM. Reason: typo
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