"Greg Copeland" wrote:

Actually, I believe you are incorrect. That passage only implies the
belt will move inversely proportional to the wheels on the plane;
What problem are you reading? The one I saw said "An airplane on a
runway sits on a conveyer belt that moves in the opposite direction at
exactly the speed that the airplane is moving forward." I didn't see
anything about wheel speed mentioned or implied. If you inferred it,
I'd suggest that is a product of your inference, not of the author's
implication.

meaning the delta is conantly zero.
What delta?
They never actually state the
plane is moving forward.
That's true. One does have to make the radical assumption that the
question is not about a plane parked on a non moving treadmill.

Thus, with a wheel speed of zero, the delta
is still zero. Therefore, I would suggest the only correct answer,
based on that sole passage is, "no".

Now, if we look at the actual question posted on straight dope, the
answer is, "maybe", for many reasons. Having said that, we can
*easily* tear up the explanation provided on straight dope. Simple
fact is, Cecil makes a huge assumption which causes his whole house of
cards to come tumbling down. Simply stated, there is nothing which
precludes the belt from being motorized.
In fact, I would argue that it would need to be motorized to go
backwards at the same speed at which the plane is moving forward. In
what way does that "cause the whole house of cards to come tumbling
down"?

Given a sophisticaed enough
implementation, one can absolutely state, the plane would never leave
the ground; assuming no head wind is involved.

Long of the short, there is simply not enough information to provide an
exact answer, other than maybe. If the belt is not motorized, AND the
plane is moving (positive delta), yes, the plane will fly. If the belt
is motorized, and it is intelligent enough to ensure a belt/wheel delta
of zero, no, the plane will never fly.
Of course, if it did that, it would assure that the plane did not move
forward, thus meaning that the belt would not move forward, which is
back to your rather uninteresting parked plane analysis. I think it
far more likely that the problem intended what it said, that the
conveyor moves backward at the same rate the plane moves forward,
rather than your different problem statement having to do with wheel
speed.


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