Before reading on, visit this puzzle post by Jason Kottke about a plane on a conveyor belt. Read it? Thought about it? Or are you as confused as many of the commenters on his post?

My initial answer to the question was that the plane would not take off. I assumed that the conveyor belt kept the plane stationary relative to the ground. And if the plane is not moving relative to the ground and assuming that the air is still, no air is rushing past the wings of the plane to give it lift. Almost everyone agrees that if the plane were not moving relative to the ground, the plane would not take off.

But, the crucial part of the puzzle is the fact that the wheels of a plane are free-spinning wheels. They are designed to move on their own accord with little friction from the axle.

Since the purpose of propellers or jet engines is to move the plane forward relative to the air (thereby creating a “relative” wind on the wings providing lift), it doesn’t matter if the conveyor belt were moving backwards from the plane. Because of the free-spinning wheels, the motion of the conveyor belt will not affect the forward thrust of the jet engines. So I am convinced that the plane will take off.

What do you think?