Airplane on a Conveyor Belt...

[eskimo2]

Originally posted by eskimo2
SaburoS,
Back to the beginning, suppose we take the wheel out of the question:

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 speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

What happens?

Please answer the question; does the plane take off or not?  

I need to know if you understand this version of the question.

[SaburoS]

Originally posted by eskimo2
Please answer the question; does the plane take off or not?  

I need to know if you understand this version of the question.

(Sigh!)
Reposting this:

Eskimo,

Example one:
A plane is on the runway that has a conveyor system that is designed to counter the forward movement of the plane using greater force as necessary where the conveyor controls the speed where it can maintain an acceleration so great that the plane's wheel's rotational inertia overcomes the thrust of the plane's engines to keep it at zero ground speed. Is this likely?

Yes. I've understood this from the beginning.

Notice that the conveyor is dictating the force here.

I just don't see this coming from the original question.

[AKIron]

Originally posted by SaburoS
No energy is lost. But that's not the question. Kind of like saying you are in a small dingy and you blow on the sail. Do you move forward based on that action alone?

What dictates wheel speed in our original question?
The plane's forward movement or the conveyor belt?

1. The plane moves forward an inch at a speed of 1 mph.
2. The belt "sees" this and moves backward at 1 mph.
3. Because the plane was moving at 1 mph and the belt is moving in the opposite direct at 1 mph the wheel is now spinning at 2mph
4. The belt sees that and increases it's speed to 2 mph
5. The plane is still moving forward at 1 mph but the wheels are now spinning at 3mph
6. The belt sees this and increases it's speed to 3mph
7. The plane is still moving at 1mph but the wheels are now spinning at 4mph

I think you can see where this is going.

This all happens very fast, limited only by the belt's ability to accelerate.

The belt only slows when the plane cannot overcome the energy being imparted to the wheels and slows. As the belt slows the plane inches forward repeating steps 1 through maximum power of the plane

[eskimo2]

Originally posted by SaburoS
(Sigh!)
Reposting this:

Eskimo,

Example one:
A plane is on the runway that has a conveyor system that is designed to counter the forward movement of the plane using greater force as necessary where the conveyor controls the speed where it can maintain an acceleration so great that the plane's wheel's rotational inertia overcomes the thrust of the plane's engines to keep it at zero ground speed. Is this likely?

Yes. I've understood this from the beginning.

Notice that the conveyor is dictating the force here.

I just don't see this coming from the original question.

I’m not asking you to comment at all on the wheel speed question.  Please forget about it for one post and answer this plane-speed question only:

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 speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

If you are really tired of it, just say, “It flies”. Or “It does not fly”.

[SaburoS]

Originally posted by AKIron
1. The plane moves forward an inch at a speed of 1 mph.
2. The belt "sees" this and moves backward at 1 mph.
3. Because the plane was moving at 1 mph and the belt is moving in the opposite direct at 1 mph the wheel is now spinning at 2mph
4. The belt sees that and increases it's speed to 2 mph
5. The plane is still moving forward at 1 mph but the wheels are now spinning at 3mph
6. The belt sees this and increases it's speed to 3mph
7. The plane is still moving at 1mph but the wheels are now spinning at 4mph

I think you can see where this is going.

This all happens very fast, limited only by the belt's ability to accelerate.

The belt only slows when the plane cannot overcome the energy being imparted to the wheels and slows. As the belt slows the plane inches forward repeating steps 1 through maximum power of the plane

The plane is still accelerating but you fail to factor that in your equation above.
The wheels are free wheeling, not powered.

Plane takes off.

[WWhiskey]

the original question  from the Neal Boortz show that started this whole thing

" If an airplane is on a large conveyor belt and is trying to take off by exerting the thrust needed to move forward at 100knots, and the conveyor belt starts moving backwards at 100 knots, will the plane be able to take off, or will it just sit stationary relative to the ground, with the backwards speed of the conveyor belt counteracting the forward thrust of the plane?"

that is all it asks, nothing more, nothing less.
 the plane will fly!
where everyone got the rest of the problems for this riddle is from other peoples answers and solutions to a problem that did not exist in the original question!

http://txfx.net/2005/12/08/airplane-on-a-conveyor-belt/
this shows the original question from december of 2005

[SaburoS]

Originally posted by eskimo2
I’m not asking you to comment at all on the wheel speed question.  Please forget about it for one post and answer this plane-speed question only:

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 speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

If you are really tired of it, just say, “It flies”. Or “It does not fly”.

Your question is vague.
I answered that if the ground speed is zero then, no, the plane will not fly. No one disputes that.

edit: Eskimo, my response did mention ground speed, not wheel speed.

[AKIron]

Originally posted by SaburoS
The plane is still accelerating but you fail to factor that in your equation above.
The wheels are free wheeling, not powered.

Plane takes off.

I kept it simple. An accelerating plane will only cause the belt to accelerate faster.

Watch Eskimo's belt sander video and tell me why the wheel moves in the direction of the belt if it is "free wheeling". It requires a force to keep it from rolling off the sander. In his case it is a spring. In the case of the plane it is the engine.

[SaburoS]

Originally posted by AKIron
I kept it simple. An accelerating plane will only cause the belt to accelerate faster.

Watch Eskimo's belt sander video and tell me why the wheel moves in the direction of the belt if it is "free wheeling". It requires a force to keep it from rolling off the sander. In his case it is a spring. In the case of the plane it is the engine.

Sorry but in this case, the belt controlled the speed. It didn't match wheel speed but dictated it. Apples and oranges.

[eskimo2]

Originally posted by SaburoS
Your question is vague.
I answered that if the ground speed is zero then, no, the plane will not fly. No one disputes that.

edit: Eskimo, my response did mention ground speed, not wheel speed.

So you think in this question, the plane won't fly?  What keeps it from flying?

[AKIron]

Originally posted by SaburoS
Sorry but in this case, the belt controlled the speed. It didn't match wheel speed but dictated it. Apples and oranges.

The belt does cause the speed of the wheel to increase by matching it. However, it is the plane that dictates this. The belt only responds to the planes movement.

[SaburoS]

Originally posted by eskimo2
So you think in this question, the plane won't fly?  What keeps it from flying?

From my example where the conveyor can use a force that keeps the plane at zero airspeed then it will not fly.
I'm saying that allowing a greater force to bring the plane back to zero ground speed is not matching anything but exceeding it. If we allow the conveyor belt to do this then it has the force/energy necessary to keep the plane back.
In this case though it is not matching.

[SaburoS]

Originally posted by AKIron
The belt does cause the speed of the wheel to increase by matching it. However, it is the plane that dictates this. The belt only responds to the planes movement.

I was talking about the sanding belt in Eskimo's video.

[Brownshirt]

Originally posted by eskimo2

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 speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

What happens? [/B]

Plane takes off without any problems. Next question.

Aircaft really doesn't care if the runway is moving or not; that can be seen pretty well in carrier take-offs and landings.

[eskimo2]

Originally posted by SaburoS
From my example where the conveyor can use a force that keeps the plane at zero airspeed then it will not fly.
I'm saying that allowing a greater force to bring the plane back to zero ground speed is not matching anything but exceeding it. If we allow the conveyor belt to do this then it has the force/energy necessary to keep the plane back.
In this case though it is not matching.

I don't think you've read the question carefully.  Please do not skim it.  This is not your example and it is not the question where the conveyor matches the wheel speed.  Please read carefully and try to understand what THIS question is asking:

"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 speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill."