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I believe this may be the problem of some to comprehend the terms of the original word problem. My answer still stands with the understanding that

A) The experiment begins with zero work (aircraft engines off, conveyor belt off)
B) No wind
C) Zero friction in the wheels
D) Ground speed is understood as relative to a point on the ground - not on the conveyor
E) Infinite technology to commence the experiment I.E. (and by far the most important) the conveyor belt moves exactly to the induced speed of the plane at precisely the same time.

Gravity holds the plane to ground. The free spinning wheels are a conveyor in themselves - allowing the plane to create forward motion without (in our case) any friction.

In our windless scenario the thrust has to propel this object forward to take off speed - which is also ground speed.

Now remember the original post? The conveyor matches the speed of the plane. All you Yes-It-Willers are assuming that at some point the planes thrust overpowers the the speed of the belt. It doesn't. It aint going anywhere. And in fact the conveyor will hardly move.

Again I defer to my R/C airplane experiment -

1) Hold it above your head at full throttle and let it go - that thing on your head will be mercilessly beat <img src="/forums/images/graemlins/butwiggle.gif" alt="" />.

2)Now step on a 500ft treadmill, power it up and start running matching speeds so you remain stationary relative to a linear space (on the ground NOT the treadmill), hold the plane above your head and gently let go - again you will feel pain.

3)Now get on it again. Put the treadmill on slow and start running. Eventually if you are fast enough you will gain enough speed over the treadmill to provide enough airflow over the wings to produce lift - the ground speed (speed relative to the ground NOT the treadmill) is equal to the TakeOff speed. If you let go the plane will fly away.

BUT #3 IS NOT THE SITUATION POSTED IN THE PROBLEM

This riddle is #2.

If I still haven't converted you there is no hope.

There is nothing new under the sun

Can we beat 400 pages? <img src="/forums/images/graemlins/pfft.gif" alt="" />

The prime mover is indeed coupled to the treadmill thanks to gravity - the entire craft is one body, one object, one piece of mass - how are the wheels magically independent of the rest of the mass that it shares?

If I wasnt clear enough - do the said experiment with open palm - plane resting on the palm. <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

If I wasnt clear enough - do the said experiment with open palm - plane resting on the palm. <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

The fact that the airplane hits you in the head at that point is simply because there is not enough lift achieved by the time it runs off of your hand to overcome gravity.

Maybe that experience would be your equivalent of Newton's apple. Maybe you should try it... <img src="/forums/images/graemlins/butwiggle.gif" alt="" /> <img src="/forums/images/graemlins/pfft.gif" alt="" /> <img src="/forums/images/graemlins/lol.gif" alt="" />

In the case of the riddle it is because the work done by the thrust of the engine is cancelled by a spontaneous equal and opposite reaction.