Will it take off?

I am now unsure, if the plane is stationary relative to the ground where does the lift come from?

I understand that its the thrust from the plane that is moving the aircraft not the wheels but it would still need some airflow over the wings to get lift. So it would need to actually be moving forward even if it was for a few meters before it lifted off the conveyer belt..
 
Liam said:
I am now unsure, if the plane is stationary relative to the ground where does the lift come from?

I understand that its the thrust from the plane that is moving the aircraft not the wheels but it would still need some airflow over the wings to get lift. So it would need to actually be moving forward even if it was for a few meters before it lifted off the conveyer belt..
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The plane will easily move forward and get it's desired lift to take off and as you say the wheels contribute nothing to the movement of the aircraft (y)

The sticking point in the discussion seems to be the wheels :cool:
 
Splog said:
The plane will easily move forward and get it's desired lift to take off and as you say the wheels contribute nothing to the movement of the aircraft (y)

The sticking point in the discussion seems to be the wheels :cool:
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You have just said that the plane will move forward, I thought it wasn't allowed to do this..,.?

I have this vision of a plane on a conveyer belt suddenly taking off but I can only see it moving forward on the belt and then taking off.
 
Liam said:
You have just said that the plane will move forward, I thought it wasn't allowed to do this..,.?

I have this vision of a plane on a conveyer belt suddenly taking off but I can only see it moving forward on the belt and then taking off.
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Remember that the conveyor belt will be running in the opposite direction to the planes wheels rotation i.e. backwards at the same speed :)
 
Splog said:
The plane will easily move forward and get it's desired lift to take off and as you say the wheels contribute nothing to the movement of the aircraft (y)

The sticking point in the discussion seems to be the wheels :cool:
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Thrust from the plane will make the wheels turn as the friction in the wheel bearing is less the the friction between the tyre and the conveyor, just as it makes the wheels turn on a proper runway - can we agree that?

The control mechanism you describe is impossible as it cannot sense the movement and react to counter it instantly, c intervenes, there has to be some lag. Lets say it is one nanosecond, that is about as close to instant as you can hope for.

Lets say the cicumference of the tyre is 1m. In the first second after the engine is turned on the tyre rotates 360 degrees. In that same second (with one nanosecond lag), the hypothetical control mechanism on the conveyor moves the surface one metre in the opposite direction. Where is the plane now, relative to where it started? If it is not in the same place (to within 2x10^-9 metres), please explain where it is, with reference to the conditions you laid down at the start, because in that case I will have completely misunderstood your description of the experiment.


Actually, the newly functional LHC will create a mini black hole that will swallow up the plane and in an amazing co-incidence I will find the missing massive scalar boson predicted by Peter Higgs down the back of my sofa, thereby proving the Standard Model. Physics will be solved and planes will be obsolete because we will have teleporters.
 
onomatopoeia said:
Thrust from the plane will make the wheels turn as the friction in the wheel bearing is less the the friction between the tyre and the conveyor, just as it makes the wheels turn on a proper runway - can we agree that?

:LOL: nope, can't agree at all :) Oil on oil = low friction, rubber on rubber = high friction .. You appear to have completely reversed your own logic i.e. if there is no or low friction then you will get slip, let me put it this way, there is no force to turn the wheels, just because the aircraft is moving forward it does nothing whatsoever to turn the wheels other than the wheels are rolling on the belt! ... now if the belt is running in the opposite direction what it is actually doing is simply turning the wheels at a constant.. the only possible force (of any significance) if the wheels are turning is from the belt, the speed of the wheels in any direction has absolutely no effect on the planes ability to push or pull itself through the air


The control mechanism you describe is impossible as it cannot sense the movement and react to counter it instantly, c intervenes, there has to be some lag. Lets say it is one nanosecond, that is about as close to instant as you can hope for.

It doesn't have to react instantly as the wheels and belt are actually independent of each other i.e. there is no mechanical linkage other than grip / friction, also the conveyor could not react instantly.. anyway it is totally irrelevant and moot as the wheels do not interfere with the planes ability to move forward or not!


Lets say the cicumference of the tyre is 1m. In the first second after the engine is turned on the tyre rotates 360 degrees. In that same second (with one nanosecond lag), the hypothetical control mechanism on the conveyor moves the surface one metre in the opposite direction. Where is the plane now, relative to where it started? If it is not in the same place (to within 2x10^-9 metres), please explain where it is, with reference to the conditions you laid down at the start, because in that case I will have completely misunderstood your description of the experiment.

I think here is where you have confused yourself ;) The plane is only moving relative to the air around it and has nothing whatsoever to do with the ground (or belt) other than from a visual viewpoint


Actually, the newly functional LHC will create a mini black hole that will swallow up the plane and in an amazing co-incidence I will find the missing massive scalar boson predicted by Peter Higgs down the back of my sofa, thereby proving the Standard Model. Physics will be solved and planes will be obsolete because we will have teleporters.

:LOL:
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I'm a computer systems engineer :p. I can only count up to 1 ;).
 
onomatopoeia said:
I'm a computer systems engineer :p. I can only count up to 1 ;).
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:LOL: (y)


Gary said:
my goodness, is this thread still going? LOL

i'm shocked splog hasnt lost his rag with some of you lot LOL
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:) No need to get wound up .. I love discussions such as this ... :D

Shame the doubters (those who are wrong) have dropped out .. ;) ... :naughty:
 
This thread just took 10 years off my brain life...
 
Splog said:
Shame the doubters (those who are wrong) have dropped out .. ;) ... :naughty:
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But there are no doubters so far (there can't be, because you haven't offered any facts/opinions/physics to doubt). Only those that trust physics, and those that are keeping quiet. "(Those who are wrong) " need some proof otherwise (whether based on physics or not) before they can concede that they are wrong. There are loads of opinions supporting the "doubters", but no opinions supporting your argument, aside from from you saying "you are wrong". I'm still lurking, but busy chatting to a mate on another forum. I've not dropped out. Just waiting until I'm at work before I start chatting about pointless (yet entertaining) stuff. :D
 
GrittyShaker said:
But there are no doubters so far (there can't be, because you haven't offered any facts/opinions/physics to doubt). Only those that trust physics, and those that are keeping quiet. "(Those who are wrong) " need some proof otherwise (whether based on physics or not) before they can concede that they are wrong. There are loads of opinions supporting the "doubters", but no opinions supporting your argument, aside from from you saying "you are wrong". I'm still lurking, but busy chatting to a mate on another forum. I've not dropped out. Just waiting until I'm at work before I start chatting about pointless (yet entertaining) stuff. :D
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Thanks for keeping up :D ... not really sure how you can say I haven't offered any facts or opinions as my posts are full of them! .. regarding physics I have yet to see a single post that references actual physics? other than mine regarding friction (fairly tenuous (as in lacking clarity) which, I admit)

When you say 'my argument' I assume this is about the discussion regarding the wheels running twice as fast as the conveyor belt :thinking: but nobody has explained why the wheels will overcome the resistance of the belt or what actually turns / drives the wheels? .. It is after all a fairly simple question :shrug:

Looking forward to your reply :D
 
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Splog said:
When you say 'my argument' I assume this is about the discussion regarding the wheels runningbut nobody has explained why the wheels will overcome the resistance of the belt or what actually turns / drives the wheels? .. It is after all a fairly simple question :shrug:

Looking forward to your reply :D
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The wheels aren't driven, as such. It doesn't really matter about the wheels and belt. The plane will fly regardless. It's just the argument about which way, and at what speed the wheels will spin that's causing the confusion.

If the plane is travelling forwards, and the wheels are travelling forwards, but the conveyor is travelling backwards, the wheels will be going faster than the conveyor.

Is the point that the wheels will be battling with friction and rearward motion?

I don't really care anymore. I'm just here to ogle your avatar. :D
 
GrittyShaker said:
The wheels aren't driven, as such. It doesn't really matter about the wheels and belt. The plane will fly regardless. It's just the argument about which way, and at what speed the wheels will spin that's causing the confusion.
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(y) This is really what makes the whole discussion interesting..... :D:

Glad to hear it's gone from facts to confusion :D
 
right so the belt is on frictionless rollers?

in which case the plane will take off slightly quicker than it would if there were no belt and it were on tarmac

really don't understand the question tbh
 
david1701 said:
right so the belt is on frictionless rollers?
Is it? , who said that? ..


in which case the plane will take off slightly quicker than it would if there were no belt and it were on tarmac
now I'm confused!... sorry but I don't understand this:shrug:


really don't understand the question tbh

What question don't you understand .. ?? ... :thinking:
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nikthomas said:
It will work, they proved it on mythbusters with a real plane!!!
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Yes it did but that plane moved forward relative to the ground, therefore it had air flow over its wing which provided the lift. If I understand the question correctly its not allowed to do this, the plane has to levitate off the belt...
 
Liam said:
Yes it did but that plane moved forward relative to the ground, therefore it had air flow over its wing which provided the lift. If I understand the question correctly its not allowed to do this, the plane has to levitate off the belt...
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Not sure where your getting this from? ... The plane can and will move forward!
 
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So if the plane is allowed to move forward on the belt relative to the ground then of course it will take off.
 
As the plane moves forward the wheels spin more quickly, which in turn causes the belt to move more quickly. As the software reading the wheel speed and controlling the belt speed catches up with the physical paradox, the wheels will theoretically spin to an infinite speed. In practice though, I imagine the tyres will just burn up, or the undercarriage will just collapse under the strain, and the plane will skid along the (now stationary, as the wheels are no longer turning, and are on the floor at the side of the runway) belt on its belly in an undignified manner, with all passengers screaming at the pilot, wondering why he hasn't noticed the disaster, or even why he attempted to take off on a backward moving runway with such software installed in the first place. "Why?! Why, Captain Splog?!" they would shout. "We only wanted to go to Benidorm".

Am I any closer?
 
GrittyShaker said:
As the plane moves forward the wheels spin more quickly, which in turn causes the belt to move more quickly. As the software reading the wheel speed and controlling the belt speed catches up with the physical paradox, the wheels will theoretically spin to an infinite speed. In practice though, I imagine the tyres will just burn up, or the undercarriage will just collapse under the strain
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I said this about 20 pages back, apparently it's wrong. I'd say it's correct.

I should give up, the OP is unwilling to explain his reasoning or even how the plane can move relative to a fixed object given the experimental parameters he laid down, never mind take off.

If the experiment were defined correctly, the plane would take off, because it is not wheel driven.
 
onomatopoeia said:
I said this about 20 pages back
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I know. (y)

But prior to this I was treating it as though the OP means that the belt will move at the same speed as the wheels, which we know to be impossible in all circumstances but when the plane is stationary. That's why my argument for the most part has been that "it's impossible".

I'm changing tack now, and treating it as though the mythical device will do its best to match the plane's wheel speed, but will fail along with the plane's undercarriage.
 
No. No airflow over the wings = no lift generated.
 
onomatopoeia said:
I should give up, the OP is unwilling to explain his reasoning or even how the plane can move relative to a fixed object given the experimental parameters he laid down, never mind take off.

If the experiment were defined correctly, the plane would take off, because it is not wheel driven.
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So why do people keep saying the wheels will turn twice as fast as the belt? to the best of my knowledge a wheel can't turn unless it's being driven and just to pre-empt the thrust from the engines answer, which would be wrong! If it was thrust then would the wheels continue to turn at the planes velocity when the plane was airborne?

A few points I have made that have not been answered, but are key to understanding the problem:

The aircraft cannot possibly turn the wheels.

What turns the wheels?

The wheels are actually irrelevant to the behaviour of the aircraft as is the conveyor

The aircraft is moving through the air, the wheels etc. are only there to keep it off the ground.
 
The thrust from the engines causes the plane to move forward, and the friction between the wheels and the belt causes the wheels to spin.

If we ignore bit about the belt moving at the same speed as the plane's wheels, and stick with the notion that the belt moves at the same speed as the plane, as the plane moves forward the belt moves backward at the same pace as the plane, which causes the wheels to spin at twice the speed they would if the ground was stationary.

Once the plane leaves the ground, there are no longer any notable forces on the wheels, so they stop spinning.

Yes, the conveyor has no effect on the behaviour of the plane, but it does have an effect on the behaviour of the plane's wheels.

But all of that changes completely with your model, because the belt matches (or tries to match) the speed that the wheels are turning rather than the speed that the plane is moving.
 
GrittyShaker said:
The thrust from the engines causes the plane to move forward, and the friction between the wheels and the belt causes the wheels to spin.
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Spot on (y) Here we agree. The wheels spin because of the massive friction between the wheel and the conveyor. The wheel is free to spin on it's bearings because there is virtually no friction at all! .... ? So there is no force acting on the wheels other than the belt, The miniscule friction in the wheel bearings would not be able to overcome the high friction between the belt and the wheel :thinking: Therefore the belt and the wheel would be turning at the same speed"
 
GrittyShaker said:
Once the plane leaves the ground, there are no longer any notable forces on the wheels, so they stop spinning.
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Which proves that the thrust or velocity of the plane has no effect on the wheels (y) Therfore cannot make the wheels turn twice as fast :)
 
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It's the movement of the plane in relation to the belt, combined with the friction of the belt, which makes the wheels spin twice as fast. Plane goes forwards, belt moves backwards, wheels spin at the combined speed of the two.
 
right either the belt is driven forwards at the same speed as the wheels, in effect halving the wheel velocity. Going backwards at the speed of the wheels, doubling wheel velocity. or not really moving

I dislike this game
 
GrittyShaker said:
It's the movement of the plane in relation to the belt, combined with the friction of the belt, which makes the wheels spin twice as fast. Plane goes forwards, belt moves backwards, wheels spin at the combined speed of the two.
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The only way this can work is if the wheels are travelling over the belt but this can't happen as there is no force / drive on the wheels from the aircraft and as was said earlier the only true force is from the belt against the wheels! The belt has its own power the wheels have none and the belt speed matches the planes wheels thus adding drive to the wheels in the opposite direction.
 
The wheels are travelling over the belt. They're attached to a forward moving plane, so it absolutely can - and will - happen!

There is friction from the moving belt against the wheels. We know this. There is another force, and it is a big one. Thrust from the plane engines, which moves the plane forward, bringing its securely attached wheels with it, as they roll along the belt in the opposite direction to its movement. The wheels have no drive, we both agree, but that doesn't stop other forces having an effect on them.

If my car's engine isn't running there is no drive to the wheels either, but if I take the handbrake off and push it you can be damn sure the wheels will rotate!
 
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