re: Can this 747 take off?

quote:

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The thrust from the engine and the motion from the treadmill in the opposite direction arent equal though. Thats where you are messing up. The treadmill and the free spinning wheels cancel out allowing the forward thrust from the engines to prevail.

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The only reason the wheels are moving is because the thrust moves the plane forward. The treadmill matches that forward movement equally but in the opposite direction. That means the plane does not move anywhere.

The riddle says it matches the speed of the wheels, which is why there is no forward movement. The speed of the wheels are what move the plane forward relative to the ground. If the "ground" moves in response to that wheel movement then the plane can't move along the ground and therefore never generate lift from the wings.

The analogy of the rope and skateboard does not work because the plane and treadmill are a closed system and the rope is applying a force outside of the system