Airplane on a Conveyor Belt...

[eskimo2]

Originally posted by VERTEX
Let me ask another question, what do you think would happen if the bearings were frictionless, and the wheels had zero mass?

The conveyor would jump to light speed/infinity instantly and the plane would take off almost normally.  (not counting for the conveyor expanding/exploding due to hitting light speed, etc...  It would have to be massless too.)

[john9001]

you mean like chuck's airplane?

[eskimo2]

Originally posted by john9001
you mean like chuck's airplane?

Yes

[eskimo2]

Originally posted by VERTEX
1 - If we put your airplane with you in it on the conveyor as specified in the original question will you be able to get to rotation speed and fly away?

2 - You are correct in theory that a conveyor could be set up to accelerate at a rate that would prevent take off, but you could not overcome the practical engineering challenges to make it real.

3 - When I say the plane flies I am referring to the original question.

This is the original AH BBS question from last year:

Originally posted by rabbidrabbit
A plane is standing on a runway that can move like a giant conveyor belt. The plane applies full forward power and attempts to take off. This conveyor has a control system that tracks the plane's wheel speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

The question is:

Will the plane take off or not?

However, we found out that a simpler version of the question had been around the net since about 2005.  This one had the conveyor matching the plane's speed.  This is much like the one that Mythbusters tested, I believe.

So, by original, which are you referring too?

[VERTEX]

Originally posted by eskimo2
The conveyor would jump to light speed/infinity instantly and the plane would take off almost normally.  (not counting for the conveyor expanding/exploding due to hitting light speed, etc...  It would have to be massless too.)

Thats just silly.

What would really happen is there would be a zero backward motion imparted to the airplane because friction and inertia would be eliminated.

[hitech]

Originally posted by VERTEX
1 - If we put your airplane with you in it on the conveyor as specified in the original question will you be able to get to rotation speed and fly away?

2 - You are correct in theory that a conveyor could be set up to accelerate at a rate that would prevent take off, but you could not overcome the practical engineering challenges to make it real.

3 - When I say the plane flies I am referring to the original question.

1. If you are speaking of the wheel speed version, I submit that there is not a control system that can be conceived to do what it ask. Assuming wheel speed is the speed of the tread the only time the speed of the belt can match the speed of the wheel is when the plane is not moving. When the plane is not moving the belt speed will always match the plane speed. Any other time (assuming the wheel does not slip on the belt) the speeds can not match.

So in the end I say the question is not valid and hence has no answer.

You would have to state the question in terms of force not speeds.

If you are referring to the Myth buster question of belt speed = plane take off speed. Then of course it will take off.

[eskimo2]

Originally posted by VERTEX
Thats just silly.

What would really happen is there would be a zero backward motion imparted to the airplane because friction and inertia would be eliminated.

I said "the plane would take off almost normally."

[eskimo2]

Originally posted by hitech
1. If you are speaking of the wheel speed version, I submit that there is not a control system that can be conceived to do what it ask. Assuming wheel speed is the speed of the tread the only time the speed of the belt can match the speed of the wheel is when the plane is not moving. When the plane is not moving the belt speed will always match the plane speed. Any other time (assuming the wheel does not slip on the belt) the speeds can not match.

So in the end I say the question is not valid and hence has no answer.

You would have to state the question in terms of force not speeds.

If you are referring to the Myth buster question of belt speed = plane take off speed. Then of course it will take off.

How about like this:

A plane is standing on a runway that can move like a giant conveyor belt. The plane applies full forward power and attempts to take off.  This conveyor has a control system that tracks the plane's wheel speed and (with a short reaction time) tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

The question is:

Will the plane take off or not?

[VERTEX]

A better question eskimo is what do YOU think?

[VERTEX]

Originally posted by eskimo2
I said "the plane would take off almost normally."

The conveyor light speed thing is silly.

[Holden McGroin]

Originally posted by eskimo2
How about like this:

A plane is standing on a runway that can move like a giant conveyor belt. The plane applies full forward power and attempts to take off.  This conveyor has a control system that tracks the plane's wheel speed and (with a short reaction time) tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

The question is:

Will the plane take off or not?

Why don't we have a more generalized question like:

Can we make an impossible situation possible... and then is it still an impossible situation, or is the premise itself an unsolvable paradox?

[hitech]

Eskimo: It still does not make any sense. When the conveyor speeds up the wheel speeds up, hence once the plane starts to move a system can never do what is stated to make the speeds exactly match. By definition the wheel speed = Plane speed + Conveyor speed. So Conveyor speed only = P + C when P = 0.

It has nothing to do with a delay, every thing to do with definition.

Also how you state the original question of plane speed also does not make any sense if the belt was to ever hold the plane, because it would mean the belt had to not move for the plane to not move. Once again a bad question with out an answerer.

Notice how the Myth Buster avoided this problem by stating conveyor at Take off speed.

[eskimo2]

Originally posted by VERTEX
The conveyor light speed thing is silly.

Why?


When the plane rolls forward, the conveyor can only speed up in attempt to match the wheels speed.  It never will since the wheel has no mass.  How long it takes to reach light speed or infinity would be derived by how quick its reaction time is.  Since it is designed to match the plane’s wheel speed exactly, it must have a perfect, or instant reaction time.  This would drive it to light speed or infinity instantly.

[VERTEX]

Originally posted by eskimo2
Why?


When the plane rolls forward, the conveyor can only speed up in attempt to match the wheels speed.  It never will since the wheel has no mass.  How long it takes to reach light speed or infinity would be derived by how quick its reaction time is.  Since it is designed to match the plane’s wheel speed exactly, it must have a perfect, or instant reaction time.  This would drive it to light speed or infinity instantly.

Read Hitech's post.

[VERTEX]

Time for a new question:

Lets say eskimo can run 10 times faster than a turtle, and he gives the turtle a 100m head start.

At the start of the race eskimo makes up the 100m but the turtle runs another 10m, eskimo runs the 10m but the turtle runs another 1m, eskimo runs the 1m but the turtle runs 1/10m, etc etc, ad infinitum.

Conclusion: Eskimo will never catch the turtle.

If this is wrong, state why.

Good luck