plane on a conveyor belt?

[Kuhn]

 you know what? If the propeller spins at the speed of light you wont be able to see it untill the future.  In real life the conveyer would make that plane nose over and crash like a bad landing.


For those who dont understand physics, youre thinking too hard about it.

I wish I was in a bar with y'all debating this. Sounds like it be a good time.

[JB88]

Originally posted by Kuhn


I wish I was in a bar with y'all debating this. Sounds like it be a good time.

i wish i was in the same bar ignoring all of you physics dweebs while making out with the hot blond in the corner.

[deSelys]

Oops, we've forgotten the aerodynamic effects induced by the conveyor belt running at the speed of light! We'd better start this thread again....


Geez, this is intellectual masturbation at its best. I feel dirty watching it...

[WhiteHawk]

Originally posted by eskimo2
Depends on the question:

If the question were that the conveyor were matching the plane’s speed in the opposite direction, the conveyor would be traveling at the rate of 50 mph at take off and so would the plane.  The plane would take off normally except its wheels would be rolling at twice their normal take off rpm.  That consumes a tiny bit of energy that really can’t be felt by the pilot.  

Conveyor matches the plane’s speed: plane will fly!

Our question, however, states that the conveyor must match the plane’s wheel’s speed.  
In this case if the plane moves forward, its wheel has gone further, and therefore faster than the conveyor.  The only thing that the conveyor can do about this is to speed up like mad!  

Conveyor matches the plane’s wheel speed: plane will NOT fly!

Ahhh, so the debat is not about the conveyor matching the plane speed, everybody agrees it would fly.  But matching the wheel speed it would not?  My bad.

[WhiteHawk]

Originally posted by Kuhn
There are too many variables added to the question at this point. If we keep adding "what ifs" or "and this too" the question can never be answered correctly. If we stick with the original question my answer still applies.  

This is true.  I dont know where all the force issues come from, but like i said, we have to assume a super wheel, and super conveyor that will hold up to heat and mechanical stress.

[WhiteHawk]

"Our question, however, states that the conveyor must match the plane’s wheel’s speed.
In this case if the plane moves forward, its wheel has gone further, and therefore faster than the conveyor. The only thing that the conveyor can do about this is to speed up like mad!"

No, no, no.  The wheel must go at exactly the same speed as the conveyor. it MUST.  Lets say the wheel moves at  1ft/sec, (I am assuming you are measuring the wheel speed along the circumference as it rotates CCW right?). then the conveyor is moving at 1ft/sec.  I  The plane speed, assuming no drag or mechanical failure is , 1ft/sec relative to a stationary object. There is no magic here, that i can see.  I am open to counter argument though.  But the WS=CS must hold true!  The question binds that.  The argument that it is impossible for the conveyor and the wheel to move at the same speed at the same time may be true, but that is not what we are given.

I think what would be happening is the wheel would be skidding along the conveyor.  But, let me tink about it .

[WhiteHawk]

Originally posted by Kuhn
 you know what? If the propeller spins at the speed of light you wont be able to see it untill the future.  In real life the conveyer would make that plane nose over and crash like a bad landing.


For those who dont understand physics, youre thinking too hard about it.

I wish I was in a bar with y'all debating this. Sounds like it be a good time.

Ok, so what drag factor would cause this nose over and where is the drag factor in the initial question?  What if the conveyor moved at 1/1000th the wheel speed?  Would there be a nose over?  Where does the conveyor speed need to be to prevent a nose over?  If there is no nose-over at CS=0, but nose over at CS=WS, there must be a critical point in between?  Help us physics tards to understand.  Obviously we are lost.

[eskimo2]

Originally posted by 2bighorn
Ok Eskimo, let me see if I got that right
You have created the problem where there isn't any. You work under assumption that conveyor possesses some fuzzy logic and is unable to match the acceleration rate of the plane therefore it outaccelerate at such rate that wheels would be spinning so fast to be able to store enough rotational energy to act as a giant flywheel resisting to any kind of movement of a plane.

Lets say it is so and that the conveyor is accelerating faster and faster and that the wheel can actually sustain unlimited rpms.

Now, device such as this fast spinning wheel would resist all latitudinal but not longitudinal change of direction of it's axis of rotation, hence if plane moves forward, it wouldn't stop it, no matter how much force you apply to conveyor, but it would resist if plane would try to weer off to the right or left.

Before you ask me where all this energy goes, let me tell you it wouldn't go anywhere. The wheel would simply store all that energy and keep rotating until all energy would slowly wear off due to friction and other smaller forces such as drag etc.

That ability to store the energy is the reason we got flywheels and they were used since centuries.

And the plane... Ahh yeah, it would still take off.

No, I didn’t create the problem; I created a solution.

Take a look at this 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.

The question is:

Will the plane take off or not?

(Note the word “wheel” has been removed)

In this situation the plane would take off normally except its wheels would be rolling at twice their normal take off rpm.  That consumes a tiny bit of energy that really can’t be felt by the pilot.  -  But wait, how can the conveyor speed be exactly the same as the plane?  If it waits for the plane to move even the slightest bit it is behind, which is not the same speed…?  Or should we just assume that the conveyor stops trying as soon as the plane moves at all?  Who cares if the conveyor matches the speed perfectly or within a millimeter or a foot?  Focusing on how it might anticipate such movement or accuracy is irrelevant.  The point is to understand that in this situation 99+ % of the airplane’s engine energy will be devoted to acceleration and increasing air resistance.

We could play with the elements of the question to help other’s understand why the plane will take off.  Such as: Suppose if the conveyor were traveling at twice the speed of the plane; In this situation the plane would take off normally except its wheels would be rolling at three times their normal take off rpm.  That would consume twice as much energy (stored in the form of rotational energy) as the same speed conveyor scenario, but it still wouldn’t be felt by the pilot.


The wheel speed question is playing by the same rules; the solution is much more difficult to comprehend however.

[eskimo2]

Steve & 2bighorn,
You interpret this question that a plane that normally takes off at 50 mph will take off at 50, and the conveyor will be going…
50?  Is this right?  Why 50?  Why not 40?  Why not 60?

[Casca]

[lukster]

Originally posted by Casca

Hope you drove a stake through it's heart.

[WhiteHawk]

Originally posted by eskimo2
No, I didn’t create the problem; I created a solution.

Take a look at this 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.

The question is:

Will the plane take off or not?

(Note the word “wheel” has been removed)

In this situation the plane would take off normally except its wheels would be rolling at twice their normal take off rpm.  That consumes a tiny bit of energy that really can’t be felt by the pilot.  -  But wait, how can the conveyor speed be exactly the same as the plane?  If it waits for the plane to move even the slightest bit it is behind, which is not the same speed…?  Or should we just assume that the conveyor stops trying as soon as the plane moves at all?  Who cares if the conveyor matches the speed perfectly or within a millimeter or a foot?  Focusing on how it might anticipate such movement or accuracy is irrelevant.  The point is to understand that in this situation 99+ % of the airplane’s engine energy will be devoted to acceleration and increasing air resistance.

We could play with the elements of the question to help other’s understand why the plane will take off.  Such as: Suppose if the conveyor were traveling at twice the speed of the plane; In this situation the plane would take off normally except its wheels would be rolling at three times their normal take off rpm.  That would consume twice as much energy (stored in the form of rotational energy) as the same speed conveyor scenario, but it still wouldn’t be felt by the pilot.


The wheel speed question is playing by the same rules; the solution is much more difficult to comprehend however.

Soo, the plane will fly should all the mechanical components hold??

[lukster]

Originally posted by WhiteHawk
Soo, the plane will fly should all the mechanical components hold??

Tell me which is greater, an unmovable object or an unstoppable force and I will give you your answer.

[WhiteHawk]

Originally posted by lukster
Tell me which is greater, an unmovable object or an unstoppable force and I will give you your answer.

Nice hijack effort.  I am trying to decipher eskimos answer as yes the plane will fly if it were possible to tune the conveyor to the wheel speed, or no it would not, even if it were possible.  Feel free to comment.

I am still trying to figure out if a tire is rotating at 1ft/sec along the circumference and a conveyor belt were moving at 1 ft/sec against the tire, it seems that the tire would trace out 2 ft/sec since it would be tracing out 1 ft per second on a stationary belt.  But if the tire were tracing out 2 ft/sec it couldnt be moving at 1ft/sec:huh   So give me some space here hunh, I am confused.  Temporarily.  Wait till the coffee soaks  in.

[lukster]

Originally posted by WhiteHawk
Nice hijack effort.  I am trying to decipher eskimos answer as yes the plane will fly if it were possible to tune the conveyor to the wheel speed, or no it would not, even if it were possible.  Feel free to comment.

It really does boil down to which is capable of the greater force, the belt or thrust. Both are variables which we may define to obtain the desired result.