Results 51 to 60 of 154
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November 9th, 2006 07:49 PM #51
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November 9th, 2006 07:51 PM #52
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November 9th, 2006 07:54 PM #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...
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November 9th, 2006 07:56 PM #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.
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November 9th, 2006 07:56 PM #55
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.
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November 9th, 2006 07:57 PM #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!
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November 9th, 2006 07:59 PM #57
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November 9th, 2006 08:01 PM #59
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November 9th, 2006 08:02 PM #60
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!Last edited by boybi; November 9th, 2006 at 08:04 PM.
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