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  1. Join Date
    Jul 2006
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    #51
    Quote Originally Posted by Alpha_One View Post
    When I said there is no wind, I meant that the wind isn't going to change it's velocity when the plane does. Planes take off perfectly fine in the real world without "wind". The engines push the plane forward and makes it's own "wind" on the wings. Your statement(s) is(are) completely fallacious in concluding that there cannot be wind against the plane.
    Planes take off perfectly BECAUSE THE RUNWAY DOES NOT MOVE! But in this case, IT DOES! Hence, it does NOT take off AT ALL!

  2. Join Date
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    #52
    Quote Originally Posted by nerbyoso View Post
    sir, nakakita ka na ba ng trick na hinila yung table cloth pero yung mga pingan at yung baso hindi gumalaw sa ibawbaw ng table? for all we know, the speed of the conveyor may even make the non-running airplane stay in place because of weight and gravity...then add power to the plane...zoom it goes.
    But it is stated that in the question, the conveyor belt matches the speed in the opposite direction! How many times will I say that? Read the original question!

  3. Join Date
    Aug 2004
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    #53
    It's simply that you have to remove the preconception that the wheels and ground have anything to do with take-off.

    Here's a simpler example. You've got a treadmill. You're running on it. The treadmill is matching your speed, so you stay in place, right? That's because you're exerting force on the treadmill (ground) with your wheels (feet).

    Now say, you're an airplane. Your hands are your engines, and the hand rails of the treadmill represent the air. Your engines push or pull against the air, and no matter what speed the treadmill is going, you can go forward or backwards on it... even if it adjusts to move forwards or backwards at the speed your body is going. Your feet (wheels) have to move faster, but your body (airplane) moves at the same speed, thus, you can pull yourself forward on the treadmill, no matter how fast the treadmill is going!

    Ang pagbalik ng comeback...

  4. Join Date
    Oct 2005
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    115
    #54
    the airplane won't fly. it needs wind to fly. if only thrust is needed for a plane to fly, so you can take out the wings and just put the engine and it can fly pero hindi pwede di ba. a stationary object cannot create its own wind. even if it is propeller driven, it cant generate enough wind to create lift from the wings. that's why you will notice that the wing flaps are longer during takeoff and landing. to create lift.

  5. Join Date
    Dec 2004
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    1,310
    #55
    Quote Originally Posted by mbeige View Post
    This is my last reply for the night, it's 3AM and I'm supposed to be in bed.

    Your freeway analogy is NOT the same. Why? Because the cars are already moving, but in this case you're starting with a NON-moving body to be compared with a NON-moving body.

    The ground is not moving against the plane in the real world, the plane moves against the ground. I did not say that the ground is moving against the wind! Where did you get that bit?
    The freeway analogy is perfectly compatible with the airplane-runway situation. We've established that the wheels only freewheel when the plane and runway move (no bearing friction at all). This effectively "disconnects" the runway from the airplane, which makes them two independent bodies. Two cars running on opposite directions on the freeway are also independent bodies.

    The ground trying to run in the opposite VELOCITY as the plane does NOT imply that the plane cannot get any velocity with respect to the air (i.e. get any wind).

    Given:
    Air velocity: 0 (This is our reference point. I'll use "air" to prevent any confusion this time)
    Airplane velocity: 100

    We can conclude at the point that the runway has a velocity of -100, given the premise. So:

    Runway velocity: -100

    Now, the crucial part:
    Airplane speed with respect to the air: 100
    Runway speed with respect to the air: 100
    Airplane speed with respect to the runway: 200 (it doesn't cancel out. The plane pass each other at 200 in the same way two cars do on the freeway)

    I didn't get any "ground moving against the wind bits". I just want you to explain how you came to the conclusion that if the runway runs against the plane, the plane can't run against the wind.

  6. Join Date
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    #56
    But it is still stated that whatever increase in speed the plane incurs, the conveyor belt matches it in the opposite direction, instantly. So whatever force the plane exerts on the wind or air, the conveyor belt will match it in the opposite direction and the plane will remain stationary!

  7. Join Date
    Dec 2004
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    #57
    Quote Originally Posted by mbeige View Post
    Planes take off perfectly BECAUSE THE RUNWAY DOES NOT MOVE! But in this case, IT DOES! Hence, it does NOT take off AT ALL!
    The speed which the runway runs, or even if it's going forwards or backwards, has absolutely nothing to do with the wind on the plane's wings!

    Good night sir.

  8. Join Date
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    #58
    Quote Originally Posted by Alpha_One View Post
    The freeway analogy is perfectly compatible with the airplane-runway situation. We've established that the wheels only freewheel when the plane and runway move (no bearing friction at all). This effectively "disconnects" the runway from the airplane, which makes them two independent bodies. Two cars running on opposite directions on the freeway are also independent bodies.

    The ground trying to run in the opposite VELOCITY as the plane does NOT imply that the plane cannot get any velocity with respect to the air (i.e. get any wind).

    Given:
    Air velocity: 0 (This is our reference point. I'll use "air" to prevent any confusion this time)
    Airplane velocity: 100

    We can conclude at the point that the runway has a velocity of -100, given the premise. So:

    Runway velocity: -100

    Now, the crucial part:
    Airplane speed with respect to the air: 100
    Runway speed with respect to the air: 100
    Airplane speed with respect to the runway: 200 (it doesn't cancel out. The plane pass each other at 200 in the same way two cars do on the freeway)

    I didn't get any "ground moving against the wind bits". I just want you to explain how you came to the conclusion that if the runway runs against the plane, the plane can't run against the wind.
    See my previous post.

  9. Join Date
    Dec 2004
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    1,310
    #59
    Quote Originally Posted by mbeige View Post
    But it is still stated that whatever increase in speed the plane incurs, the conveyor belt matches it in the opposite direction, instantly. So whatever force the plane exerts on the wind or air, the conveyor belt will match it in the opposite direction and the plane will remain stationary!
    No it doesn't. The force the plane exerts on the air is not affected in any way by the force the ground exerts. Remember, the wheels effectively isolates the plane from the ground making them two completely independent bodies.

  10. Join Date
    Oct 2002
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    19,438
    #60
    Quote Originally Posted by niky View Post
    It's simply that you have to remove the preconception that the wheels and ground have anything to do with take-off.
    in the real world, the wheels are just an aid for the jet engines to push the plane forward againts the ground. it is the speed of the airplane (generated by the jet engines) against the surrounding air that creates a lift for the airplane to take off.

    but in this situation, the airplane's speed against the surrounding air is zero. why?!?!? BECAUSE IT IS STATIONARY!

    Here's a simpler example. You've got a treadmill. You're running on it. The treadmill is matching your speed, so you stay in place, right? That's because you're exerting force on the treadmill (ground) with your wheels (feet).

    Now say, you're an airplane. Your hands are your engines, and the hand rails of the treadmill represent the air. Your engines push or pull against the air, and no matter what speed the treadmill is going, you can go forward or backwards on it... even if it adjusts to move forwards or backwards at the speed your body is going. Your feet (wheels) have to move faster, but your body (airplane) moves at the same speed, thus, you can pull yourself forward on the treadmill, no matter how fast the treadmill is going!
    because the handrails are attached to the treadmill. the air is not 'attached' to the ground or the conveyor.
    Last edited by boybi; November 9th, 2006 at 08:04 PM.

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Will the Airplane Fly??????????