Principles of flight?

[sergei]

So what I'm trying to say is:
The speed and ability to fly of the plane are NOT affected by conveyer.
The conveyer speed IS affected by plane's speed due to friction in wheels/ wheel vs conveyer and fact that wheels are attached to the plane.
The speed of the conveyer will be double but in opposite direction of the plane or will be same as plane's and in same direction deppends how the conditions are interpreted.

[V8MOFO]

Plane will take off.
But the speed of the conveyer will depend on the plane's speed (if the contradicting statement is resolved) becuase of the friction of the wheel against conveyer and wheels are attached to the plane.. (think about bearings - the actual ball/rollers/needles rotate at a speed relative to to both outer and inner shells)

Remember acceleration here. Speed is not the question. It's about acceleration.

[V8MOFO]

So what I'm trying to say is:
The speed and ability to fly of the plane are NOT affected by conveyer.
The conveyer speed IS affected by plane's speed due to friction in wheels/ wheel vs conveyer and fact that wheels are attached to the plane.
The speed of the conveyer will be double but in opposite direction of the plane or will be same as plane's and in same direction deppends how the conditions are interpreted.

Acceleration Think about it.

[sergei]

please explain why the acceleration of the conveyer belt has to do anything with stopping the plane from flying?

[sergei]

unless we are dealing with the speed close to c nothing will stop that plane flying, it does not "push" against the conveyer, it "pushes" against the air, and it does not matter if the wheels or conveyer will acclerate, it is completely separate event.
Eg: driving in car while holding the paper plane and letting it go, instead of being stationary and throwing it, in both cases it will result of the paper plane being airborn. It has nothing to do with what speed are the wheels of the car are rotating or that the road is relatinvely the paper plane going the opposite direction.

[vvega]

try pushing a toy car over a belt sander
see if it offers any resistance to you pushing it


v

[sergei]

But belt sander is not desgined to match "speed of the wheels"! and any way it will require the same force as to move with same speed relative on the ground (ie if a point on the belt sender doing 5m/s relative to the car, it will require same force to move the car on stationary sand paper with car having speed 5m/s relative to that sand paper)

[sergei]

I can't believe how many people voted NO.
I could not be stuffed reading whole 14 pages of arguments, but most of the arguments I think are in favour of plane lifting off so who voted NO?

[vvega]

But belt sander is not desgined to match "speed of the wheels"! and any way it will require the same force as to move with same speed relative on the ground (ie if a point on the belt sender doing 5m/s relative to the car, it will require same force to move the car on stationary sand paper with car having speed 5m/s relative to that sand paper)

the belt sander once turned on will match the speed of the wheels or it will sand them off
think about it

it is the same ECept the wheels are moving before you move the car




v

[sergei]

I agree that toy car wheels will match the speed of the beltsander, but not opposite... or properly to rephrase this:

The nett value of the rotational vector of the toy car at the point of the contact with the beltsander will be exactly the same as the beltsender's nett value of the rotational vector at the contact point mentioned above.

With the plane question don't forget conservation of the energy.

From my point of view, the plane question should be rephrased to correct condradiction in the part which I quoted in the posts above. It should be corrected to: "the belt will countereact the rotational velocity of the wheels", thus resulting in 0 (zero) rotational velocity of the wheels which in fact will result matching belt surface speed to plane's speed (while plane speed is independent to belt's speed, ie plane movement is the cause of the belt's movement, not opposite).

[sergei]

I sometimes follow simple rule:
If problem does not have a correct answer - change the problem so it will...

[V8MOFO]

I sometimes follow simple rule:
If problem does not have a correct answer - change the problem so it will...

If it were that simple it wouldn't be a very good question. Because there is no answer because it is impossible makes it a very good question, hell 15 pages on good question.

[vvega]

lol
yes i do know what your saing
but your been pedantic now :d

lol and i like it

v

[igor]

I sometimes follow simple rule:
If problem does not have a correct answer - change the problem so it will...

If it were that simple it wouldn't be a very good question. Because there is no answer because it is impossible makes it a very good question, hell 15 pages on good question.

The original version of the question where the conveyor matched the aircrafts groundspeed was better. :/

[V8MOFO]

I sometimes follow simple rule:
If problem does not have a correct answer - change the problem so it will...

If it were that simple it wouldn't be a very good question. Because there is no answer because it is impossible makes it a very good question, hell 15 pages on good question.

The original version of the question where the conveyor matched the aircrafts groundspeed was better. :/

That would bring similar results I'm sure. The only difference being that the wheels speed, plane ground speed and travelator speed would be the same at all times.

[Malcolm]

haha, well I'm going to add in my 2 cents now.
I read to page 9, then skipped to the last one to see if you were still arguing, and you are, so:

First I thought "no", until I quickly realised this isn't a car, Malcolm, as has been clearly stated it develops velocity by thrust, rather than by turning the wheels, and quickly realised the obvious, true answer, was yes, as has been argued extensively by vvega, RomanV, pidge, and others; anyone trying to argue that the conveyor spinning at the same speed as the wheels will stop it moving is clearly an idiot.


But then by the time I got to about page 7 or 8 I had started thinking some more.



The only way the wheels on the plane will even begin to move, is if the plane itself moves, as there is no device connected to the wheels to turn them. (this assumes the plane starts from rest with the conveyor belt not moving).

So, in an infintessimally small period of time after thrust is applied, the plane will begin to move, the instant this happens the magic conveyor belt will begin attemping to match the speed of the wheels, however if the plane has any forward motion at all, no matter how tiny it is, any attempt by the conveyor to match the speed of the wheels will result in the wheels still turning slightly faster than the belt.

To further emphasise this, here's some numbers. Lets say that the thrust has caused the wheels to reach a rotational speed which gives a linear velocity of 0.00000000001 metres/second at the edge of the wheel (and thus this is the plane airspeed). The instant that happens the conveyor attempts to match it, and also turns at a rotational speed to give a linear velocity on the belt surface of 0.00000000001m/s.

However, because the conveyor has begun rotating, the speed of the wheel will be it's previous speed, plus the speed of the belt, which means it will suddenly be 0.00000000002m/s. Because we assume the magic conveyor can actually instaneously match the speed of the wheel, but any attempt to do so results in the wheel also increasing in speed; the conveyor belt continuously attempts to make up that 0.00000000001m/s of speed that it simply cannot do, to the point where these rotational speeds would reach infinity.

Now, assuming a perfect scenario where the wheel or conveyor belt doesn't disintegrate from these speeds, the friction generated in the wheel bearings, and rolling resistance of the tyre on the conveyor would reach a value high enough to overcome the thrust from the engines (since they are rotating at infinite speed).

However, that relies on further assuming the tyre/conveyor interface could provide a high enough friction force to balance the force created by the thrust of the engines, which is not necessarily going to be the case; it is highly likely that the tyres would just skid along the surface once there was enough resistance in the wheel bearings to counteract the thrust produced by the plane's engines.


So in conclusion;

Real World: if you tried to make this for a practical experiment, the plane would take off, quite easily, although it would probably be at the expense of a conveyor belt that has broken from attempting to spin too fast, and a plane that is damaged from an exploding tyre beating the undercarriage as it came detached from the wheel at a 100,000rpm (or something).

Theoretical World: if you supposed the components wouldn't fail and the tyre wouldn't skid, once the surface of the belt reached light speed attempting to make up that last 0.00000000001m/s of speed, you might just have enough concentrated energy to cause the earth to become the second sun in the solar system, but the plane would still take off, so long as you didn't get any interesting quantum-physics-type side effects of the speed (like the matter condensing to the point that it caused an implosion and became a black hole, from which no light could escape and you could never see whether the plane managed to take off, but chances are it's part of the tiny ball of mush within the black hole)

[vvega]

i dont know if the wheels would spin malcom

you see it states it rotates in the oposite direction to the wheel movement
and is based of the wheel speed
so

plane moves this way >>>>>>>>>>>>>>>>>>>>>>>>

the contact surface of the wheel is rotaing this way <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

so the convayer moves this way>>>>>>>>>>>>>>>>>>>


now the object of the conveyer is to stop the wheel turing
so it will match the speed that the whel is turing to do this

basically if you look at it carefully and think about it
the wheel will not rotate at all
this is the funtion of the converyer

but to do this the side effect would be that the convayer would match the plane speed as it would have to be moving in the same direction as the plane

remebering that the convyer would only turn as fast as require to stop the wheel turing as that is its function

so the plane will take off
the wheels would not rotate
and the convayer would match the planes groundspeed

v

[Malcolm]

I actually thought about that, but I believe it means it goes in the opposite rotational direction, so if the plane moves this way >>>>> the wheel rotates clockwise, and the conveyor rotates anticlockwise, meaning the contact surfaces move in the same direction (this way <<<<<<)

[vvega]

that would mean that it woudl accelerat the wheel
were as the point of it was to stop the wheel moving

v

[Malcolm]

if it stopped the wheel moving, the belt would follow the plane, whereas I'm pretty sure the idea of it is the treadmill effect that people think will happen, ie spins in the opposite direction so the wheels can't go anywhere (although as I already stated, I don't think it will work, plane will still take off)