think about this...

[Patrick del Poker Grande]

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There is a plane (Boeing 777, prop plane, whatever) on a moving, conveyor-type runway. The runway moves in the opposite direction of the plane at the exact same speed as the plane's wheels. There is no wind. Can the plane take off?

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Yes.

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BIMO

[Patrick del Poker Grande]

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I finally got hooded to admit defeat. The easist way for us to think about it was the rollerskate on treadmill example. If you are pulling yourself forward on the treadmill, you are going to go forward no matter what your [censored] wheels do. you are going to move forward! the hang up is that the OP suggests that the plane somehow is not able to accellerate forward but the fact is that it WILL accellerate forward. THe only thing stopping it is the wording of the problem which suggests its going to stay in place, but taht is not what is going to happen.

edit-actually, it doesnt even say anything about that in the OP. that must have been concluded by people later in the thread.

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Good. Anyone who can't understand after thinking about the rollerskates on treadmill example or the stroller on moving walkway example is just a fool. Anyone trying to get out of this with some BS about they thought the OP said the wheel's CG is moving at the same speed as the conveyor is just an idiot trying to back out of being wrong.

[4_2_it]

Patrick, you actually enjoy watching this thing spiral out of control, don't you? I expect to see pwnage the likes of which OOT has never seen. I am looking forward to this more than I am Dominic's next porn bloopers post (well almost [img]/images/graemlins/grin.gif[/img]).

[SomethingClever]

Wait, wait, wait, wait.

I have another variable.

What if there are snakes on the plane?

[goofball]

First, assume the wheels rotate without friction.

A) If the wheels must have the same angular speed as the moving runway (as stated in the OP) the plane cannot be moving relative to the ground/air and cannot take off.

B) If the wheels can have a greater angular speed than the moving runway then the plane can take off regardless of runway speed (within reason).

Everyone can find a new subject.

[Oblivious]

The hang up is actually here:

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The runway moves in the opposite direction of the plane at the exact same speed as the plane's wheels.

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The runway can not possibly do this. Just like theres no sloution to x=x+1. We could envoke reletivity here, and say that any system that knows the speed of the wheels could not INSTANTLY communicate that speed to the system that controlls the speed of the runway. So the wheels would would be free to accellerate to infinity while the runway accellerates just a bit more slowly.

[felson]

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Doesn't:

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The runway moves in the opposite direction of the plane at the exact same speed as the plane's wheels.


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mean no net movement? Same speed, opposite direction.


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I would really like to see a response to this. So far all I'm hearing is, "the wheel speed doesn't matter, only the plane speed matters." Well, of course. But the conditions of the problem are impossible to satisfy unless the plane groundspeed is zero, or the wheels are slipping a ridiculous amount. IMO the problem is ill-posed and doesn't deserve all this attention.

I'm also confused why people say that the fan-on-skateboard contraption won't move because there is no net force on the system. Would you say the same thing if the sail were just 1 square centimeter in area? If not, then any explanation must take into account the size of the sail. I don't believe that has happened yet, except for some people who observed that the sail cannot capture all the moving air blown by the fan.

[Patrick del Poker Grande]

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Patrick, you actually enjoy watching this thing spiral out of control, don't you? I expect to see pwnage the likes of which OOT has never seen. I am looking forward to this more than I am Dominic's next porn bloopers post (well almost [img]/images/graemlins/grin.gif[/img]).

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It is pretty entertaining. This is the kind of [censored] that OOT is supposed to be about. Don't get too excited - I really don't see what's so complicated about this problem, so my explanation will be pretty simple.

Are you saying that the question really is impossible as stated, but it's just a nit and beside the point? That would clear things up for me tremendously.

[4_2_it]

I consulted another science expert and this is what he said the plane would do: