Airplane on a Conveyor Belt...

[eskimo2]

Originally posted by SaburoS
To stop that forward momentum, you have to apply a greater than matching force.

Plane flies.

So you'd give up?

I think most folks would lower their end an inch and a quarter, ease the ball back to the center and level out the trough.

[eskimo2]

Originally posted by AKIron
Just a little tangent to give us a break from this heated battle.

You're standing in boxcar that is sitting on a rail that is virtually frictionless. You're standing at one end of the boxcar and you throw a baseball at the far wall. What is the net result of this action?

Ball flies and the boxcar rolls ever so slowing in the opposite direction.

[VERTEX]

Let me correct myself, when the ball is thrown the boxcar would move in the direction you are not facing, when the ball re-bounds off the far wall the boxcar would move in the direction you are facing, if you catch the ball on its return the boxcar would come to rest again. This assumes no air friction to slow the ball, and the ball has no energy losses on the rebound.

[AKIron]

What happens when the ball hits the wall? The car stop? What if you walk over pick up the ball, walk back and throw it again? Could you move the car to California (assuming the tracks were inclined to go that way and you are a hippy)?

[VERTEX]

Originally posted by AKIron
What happens when the ball hits the wall? The car stop? What if you walk over pick up the ball, walk back and throw it again? Could you move the car to California (assuming the tracks were inclined to go that way and you are a hippy)?

When you try to walk the boxcar moves under you in the opposite direction. You stay motionless with respect to the tracks.

[eskimo2]

Originally posted by VERTEX


Just to clear up your belt sander test results, the reason the wheel is pulled back by the sander belt when its turned on is due to the inertia of the wheel at rest. The rest inertia must be overcome while the wheel spins up to belt sander speed.
 

Been there, done that, watch this:
http://hallbuzz.com/movies/wheel_on_sander_2_speed.AVI

Note the second pulse as the sander accelerates from a constant speed to a faster one.

[VERTEX]

Originally posted by eskimo2
Been there, done that, watch this:
http://hallbuzz.com/movies/wheel_on_sander_2_speed.AVI

Note the second pulse as the sander accelerates from a constant speed to a faster one.

Fine, do you agree the plane flies?

[SaburoS]

Originally posted by eskimo2
So you'd give up?

I think most folks would lower their end an inch and a quarter, ease the ball back to the center and level out the trough.

No. This isn't about giving up.

At no point does the question allow a greater force to be used. It is to match the wheel's speed. Unless the aircraft moves forward the wheel's speed is zero and the conveyor's counter speed is zero.
Unless the aircraft is accelerating the conveyor won't accelerate. Once you grasp that, you'll see where I'm coming from and why I see your reasoning as flawed.
We're not talking about a car that gets its forward movement from its wheels.

The plane flies.
The conveyor fights the losing battle for it has to react to the plane's forward movement for its speed. No forward movement/acceleration, no conveyor speed.

You just haven't grasped the fact of all the forces involved.
You keep confusing ground speed to wheel rpm speed.

Plane flies.

[eskimo2]

Originally posted by VERTEX
Actually upon thinking about it I take that back, I doubt the take off roll would change.

...

At real life scales this wheel inertia would have a minimal effect on the take off roll distance of the aircraft.

But you are right, there is an effect. But not a large enough effect to counteract the final result that the airplane would fly.
 

So which is it?

Why must the force remain small?

Imagine a question that asks, “Could a team of mice be as strong as a team of men?”  If you assume that there are the same number of mice as men, then clearly the answer is no, the men are stronger.  But “team” is not defined.  “Team” for men could be two, and “Team” for mice could be 200,000.

[eskimo2]

Originally posted by VERTEX
Fine, do you agree the plane flies?

If the conveyor matches the plane’s speed; it flies no problem.
If the conveyor matches the plane’s wheel speed; it will not fly.

[VERTEX]

Eskimo, first I need to know if you agree the airplane will fly, and if you agree with my 3 possible conveyor belt options, then I will get into the nitty gritty, with respect to the extraneous forces involved.

[AKIron]

The virtually frictionless part is kind of a rub.

You might liken this scenario to standing on a skateboard. You can shift your weight causing the skateboard to move. By slowly regaining your original position you prepare yourself to do it again without moving the skateboard in the opposite direction. You can do this because friction is working with you in this.

In a closed system without friction (yes, even without that caused by internal air I neglected to account for)  I think it would go more like this:

1. You throw the ball, the car moves +1.
2. Ball hits wall, the car stops.
3. Walk over to pick up the ball, the car moves another +1.
4. Walk back with ball, the car moves -2 (more mass moving back)

[VERTEX]

Originally posted by eskimo2
If the conveyor matches the plane’s speed; it flies no problem.
If the conveyor matches the plane’s wheel speed; it will not fly.

What can I say, the wheels rpm is indepandant from the aircrafts forward motion, the wheels free wheel on an axle, if you cant get that part its no use continuing.

[VERTEX]

The conveyor cannot match the planes speed, the free wheeling nature of the wheels prevents this, the conveyor can only act on the wheels.

[VERTEX]

The plane on a conveyor is a trick question in the first place, its like asking if a an electric train was moving forward at 50 mph and the wind was blowing in the direction the train was moving which way would the smoke move?