plane on a conveyor belt?

[Terror]

Originally posted by deSelys
LOL....It will move. Because the conveyor belt is bringing energy into an 'energy tank' (the spinning wheels) which has next to zero influence upon the other energy tank feeded by the plane engines (cinetic energy= plane mass*(plane speed squared)/2).

The next to zero influence is the friction between wheels and axles. I've looked it up and friction is max when there is no relative movement. As soon as the two objects begin to 'slip' on each other, the friction lowers a bit and stays constant. The energy generated by the friction will be turned into heat. Will heat stop the plane?

You could consider the problem like this: a truck is filled with water. As soon as the truck engine tries to move it, heaters in the water tank kick in to try and stop the truck. Will it move?

It's not a friction problem.  Its an acceleration problem.  The belt will accelerate at a much higher rate than what people are invisioning.  Its the only way the belt can perfectly match the wpeed of the wheel.  It uses the inertia of the wheel to keep the plane from moving.

Heat from friction is not considered in the original question, only the speed of the wheel and the speed of the conveyor.  Speed of wheel = Speed of conveyor.  If that stays true, then the plane cannot move.  

Do you agree with this statement?
For the plane to move forward, wheel speed would have to greater than the speed of the conveyor.

If you agree with that statement, then tell me how the the plane moves if the question clearly states that the wheel speed equals the conveyor speed.

Terror

[lukster]

Originally posted by john9001
the belt can not apply any force to the plane , all the belt can do is spin the wheels.

Watch Eskimo's videos and think about what you are seeing. All of the objects on the paper (belt) moved in the direction of the belt. It would take a force in the opposite direction to hold them stationary or move them forward. Replace the objects with the planes wheels and the force I mentioned with the plane's thrust. The faster the belt accelerates (not moves) the more force applied to the wheel.

[lukster]

BTW, I have a preciesly calibrated mk 1 eyeball and can tell you Eskimo's paper converyor belt was accelerating at almost 32ft/s/s.

[SteveBailey]

Here's the premise. The plane moves forward and the wheel is now spinning forward at 10rpm. The wheel monitor senses this and tells the belt to move in the opposite direct at 10rpm. Since the A/C engine is applying thrust at least holding the plane in place or moving forward for now, the belt now moving in the opposite direction at 10rpm causes the wheel to rotate at 20 rpm. The wheel monitor/belt controller senses this and speeds the belt to 20rpm, this increases the wheel to 40 rpm. The rate at which the belt is allowed to accelerate to it's max speed determines the force applied to the plane countering it's thrust.

There is no mention of the conveyer countering the force of the motor, only the speed of the wheels.  The conveyer is acting against the rpm of the wheel, not the thrust of the motor(per the initial post).  The only way for the wheels to be moving faster than the conveyer(causing it to accelerate) would be if the plane had a foward vector.

[lukster]

Originally posted by SteveBailey
There is no mention of the conveyer countering the force of the motor, only the speed of the wheels.  The conveyer is acting against the rpm of the wheel, not the thrust of the motor(per the initial post).  The only way for the wheels to be moving faster than the conveyer(causing it to accelerate) would be if the plane had a foward vector.

There is no mention of the conveyor "countering" anything. Only that it moves in a direction opposite at the same speed.

[SteveBailey]

So where did you come up with the belt countering the thrust of the motor?

[APDrone]

Originally posted by SteveBailey
So your answer to my debate is: since it never moves it doesn't fly.  how exactly does the conveyer keep the plane from moving? The conveyer matches the wheel speed... that means the wheels have to turn first, even if for an instant.  Which means the plane has to move forward.

You are getting somewhere if you would heed our discussion instead of worrying about "winning".

Think about the initial question.  The conveyer matches the "speed" of the wheels, not the thrust of the airplane. If the thrust of the plane is 1000 pounds at first push to full throttle, are you saying the conveyer thrusts back against the wheels at 1000 pounds? If so, what does this have to do with wheel speed, which was the original  posit?

Again, the conveyer matches the speed of the wheel.  The only way for the wheels to move is for the plane to move forward. What stops the plane from rolling forward and how?

At your request to 'heed our discussion', I will continue.

Please understand that I'm trying to graciously back out of this thread.  I'm convinced that the original question has been addressed and answered and I've spent way too much of my life restating my position.  Also, we're now starting to see people jumping into the thread and posting responses without having made the effort to read what has gone before, so we're restating and restating ad nausum.  

Now, back to how the aircraft starts.  Honestly, I don't know how it actually begins to roll in relation to the thread.  That's part of the 'It just does' part.

You're probably right in that there may be some actual initial movement,  then the conveyor would match the rotational speed and it would bring net movement back to 0. It really depends on the tolerances of the equipment used. With laser scanning and such, it could even be down to a billionth of an inch. The wheel would still be spinning and constantly accelerating, but this speed, whatever it is at a given time is matched, as stated.  Any additional acceleration would be starting with 0 net speed.  

I think I see where you're going with this.. in that, eventually, the aircraft may inch its way across the conveyor and eventually be liberated from it... at which point the normal physics kick in and it takes off normally..

Unless it is in AH's world and hits the customary tree or hill at the end of the runway.

[lukster]

Originally posted by SteveBailey
So where did you come up with the belt countering the thrust of the motor?

How else are you gonna stop the plane from moving forward? The force that counters the thrust is a result of the belt spinning to match the wheel's speed but in the opposite direction.

Adding the concept of countering the speed to the original problem is another act of interpretation. However, taken literally I think it should be interpreted to mean only two possibilities. Does the belt turn the same speed but in a direction opposite of the wheels spin, or, of the wheels forward speed through the air without regard for spin.

[SteveBailey]

How else are you gonna stop the plane from moving forward?

That's just it, the plane doesn't stop moving forward.  It accerates down the conveyer until liftoff.

[lukster]

Originally posted by SteveBailey
That's just it, the plane doesn't stop moving forward.  It accerates down the conveyer until liftoff.

Do you believe this will happen even if the conveyor belt is accelerating the spin of the wheel at a rate of say 10,000mph per second per second?

Or do you just believe the belt is only moving as fast but in the opposite direction as the plane is moving through the air?

[lukster]

Let's break it down (yes, again).

The plane moves 1 foot in one second which is the equivalent of 1 RPS. The belt controller senses this and speeds up the belt to 1 RPS in the opposite direction. If the plane does not slow, the wheel will then be sped up to 2 RPS. The belt's controller senses this and increases the belt to 2 RPS. Again, if the plane does not slow, the wheel speed is increased to 4 RPS. This happens over and over up to the speed of light theoretically. The amount of force applied is directly proportional to how fast the speed of the wheel is increased, in other words, it's acceleration.

Disclaimer: The distances given were for explanation purposes and do not accurately represnt the distances involved with the forces we're talking about. No planes were harmed in the making of this post.

[Kuhn]

The wheels wont roll if an airplane does not move forward. Being that the wheel movement is is controlled by the prop moving through the air ,the plane will move forward nomatter what the wheels are doing. The conveyer can try all it wants to keep the wheels spinning fast enough to keep up with the rotation but in no way is it possible even in theory for it to keep up with the wheel speed. It will keep accelerating as the plane moves forward and the plane will lift off. So actually the original question is flawed and cannot be answered the way it was asked. It is not possible for the plane not to move forward when the prop is pulling it through the air. It is not possible for the plane to move forward if the wheels dont rotate when in contact with the ground.

I could go on but I wont

[APDrone]

Originally posted by Kuhn
The wheels wont roll if an airplane does not move forward..Being that the wheel movement is is controlled by the prop moving through the air ,the plane will move forward nomatter what the wheels are doing   The conveyer can try all it wants to keep the wheels spinning fast enough to keep up with the rotation but in no way is it possible even in theory for it to keep up with the wheel speed. It will keep accelerating as the plane moves forward and the plane will lift off. So actually the original question is flawed and cannot be answered the way it was asked. It is not possible for the plane not to move forward when the prop is pulling it through the air. It is not possible for the plane to move forward if the wheels dont rotate when in contact with the ground.

I could go on but I wont

Explain how chocks work, then.

And brakes too, while you're there.

[Golfer]

Or a throttle lock for that matter

The agruments for the airplane not flying are getting more and more absurd

[lukster]

Originally posted by Golfer
Or a throttle lock for that matter

The agruments for the airplane not flying are getting more and more absurd

The plane cannot fly if it cannot achieve a fast enough airspeed.

To anyone who thinks an accelerating belt will not apply a restraining force on the wheels and therefore the plane please explain what it is that moves the objects on Eskimo's paper conveyor belt. If you cannot explain why they move then you cannot understand the forces involved.