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Old 03-06-2006, 11:45 AM
Ethilrist Ethilrist is offline
Join Date: Nov 2000
Location: Saint Paul
Posts: 26,319
This never ceases to amaze me. I think, in the first article he wrote, Cecil pointed out that this was intended as a thought experiment, not to find out whether or not the plane would take off, but to find out how people look at puzzles and try to solve them.

Everybody's right.
Everybody's wrong.

Interpetation #1: Assuming real-world materials and a vaguely-stated supposition that the runway moves backwards as fast as the plane moves forwards, the plane takes off, because making the wheels spin twice as fast doesn't exert enough force to stop the plane. BR #1.

Interpretation #2: Assuming non-real-world materials and the iron-clad fact that somehow the treadmill exerts enough force to keep the plane from moving, the plane does not take off, because non-moving planes don't take off without a lot of wind, and that's not in the puzzle. BR #2.

So, for all of you arguing that real-world materials behave a particular way and even if you melted the tires off the plane, it would still screech down the treadmill and take off, congratulations. You're right.

And for all of you arguing that the question states that the treadmill keeps the plane from moving, congratulations. You're right, too.

And for all of you arguing that the treadmill, moving fast enough to satisfy group #2, generates enough wind due to the laws of contagion such that the wind passing over the wings causes the plane to lift off, you're right, too, but you're cheating.