Stupid physics question

[Will]

Not again...as far as the plane is concerned, the conveyor doesn't exist. It would only stay still with the engines off.

 

[rynnor]

Flight (lift) is generated by the movement of air across the wing surface, which because of the design, generates a higher pressure below it than above it, you must have air move across a wing surface to generate lift.

It does not matter what the speed is relative to the ground, it matters what the speed is relative to the air.

A plane will fly in a wind tunnel with absolutely no propulsion or forward movement at all, gliders dont have engines, it is the movement of air across the wings that generates the lift.

No lift, no takeoff.

Aye this is the correct version - planes take off because the wing is shaped so that the air has to travel faster over the top of the wing which generates a kind of suction force - to take off the wind over the wings must be moving sufficiently fast to generate a force sufficient to lift the mass of the plane.

In this case the plane is standing still so no force to lift a plane. Its like being on the machine when you go for an MOT - the wheels are going fast but the cars not moving.

 

[rynnor]

Bugger - opposite direction - grr ;P

 

[Danya]

Aye this is the correct version - planes take off because the wing is shaped so that the air has to travel faster over the top of the wing which generates a kind of suction force - to take off the wind over the wings must be moving sufficiently fast to generate a force sufficient to lift the mass of the plane.

In this case the plane is standing still so no force to lift a plane. Its like being on the machine when you go for an MOT - the wheels are going fast but the cars not moving.

Plane's not standing still - the engines work by sucking air through, not by spinning the wheels. The conveyor belt makes no difference (OK, in the real world you'd probably blow out the wheels from them spinning too fast, but hey).
Strangely enough, plane engines work whether or not the wheels are spinning fast or slow or indeed even if they aren't touching the ground at all.

 

[tRoG]

Plane's not standing still - the engines work by sucking air through, not by spinning the wheels. The conveyor belt makes no difference (OK, in the real world you'd probably blow out the wheels from them spinning too fast, but hey).
Strangely enough, plane engines work whether or not the wheels are spinning fast or slow or indeed even if they aren't touching the ground at all.

Win!

The aeroplane moves, hence it takes off.

 

[Milkshake]

I wanna change my answer. Yes, it would take off.

 

[Sockstuff]

Just been explaining things in IRC...

[19:47] <Danya> jet engines push the air, not the belt
[19:48] <Socky|****> right i shall explain how a plane works on a runway that doesnt move
[19:48] <Socky|****> the planes sits ontop the wheels
[19:48] <Socky|****> its is fixed to the wheels
[19:49] <Socky|****> when the engines are powered up its like it is reaching out an arm and pushing against a wall behind it
[19:49] <Socky|****> allowing it to roll foward on the wheels
[19:49] <Socky|****> thus if the ground below the wheels moved backwards at the same speed as it moved foward it wouldnt move atall in thwe world
[19:49] <Socky|****> just the wheels would be spinning
[19:50] <Socky|****> if the engines worked harder to push
[19:50] <Socky|****> and the belt stayed at the same speed it would move foward ibn the world
[19:50] <Socky|****> BUT the belt speeds up making just the wheels spin
[19:50] <Socky|****> not alowing it to create any foward motion
[19:51] <Socky|****> without any foward motion on the plane there will be no air going over the wings
[19:51] <Socky|****> without air going over the wings of a plane it cant create lift
[19:51] <Socky|****> thus it will not fly
[19:52] <Socky|****> the same goes foe if a plane was trying to take off on a normal run way
[19:52] <Socky|****> if the air was moving along witht he plane at the same speed there would be no air moving over the wings
[19:52] <Socky|****> thus no lift
[19:52] <Socky|****> and the plane just runs off the runway onto the road at the end
[19:52] <Socky|****> killing everyone there to watch the plane take off

 

[Wij]

Well - if the original question had stated 'the belt is designed to match the speed of the wheels of the plane' I would then be in the yes camp. The original question, however, states that the belt matches the speed of the plane, hence one has to assume they mean the body of it, and therefore the plane would not gain any actual foward velocity, and hence it would not take off.

FFS - even the original question makes it obvious the plane would take off. How on Earth could the plane stay still on the runway if the belt is designed to match the speed of the aeroplane ? If it WAS keeping the plane in place then the speed of the aeroplane would be ZERO, therefore the belt would not move, but the belt must have been moving to keep it in place, but if it was keeping it in place then the belt could not be moving... ad infintum.

Therefore the question makes no sense but on a generous re-interpretation the plane would still take off but with the wheels spinning faster.

CLOSE THREAD NOW PLEASE !!!

 

[Danya]

Here's a thought for those who think it won't take off - what would happen if you put a plane on stilts such that it's wheels were off the ground and fired up the engines?

a) The wheels would spin manically.
b) The plane would jolt forward and topple the stilts.

Unless you think a) is correct then there's no reason why a plane on a conveyor belt would not take off.

 

[Sockstuff]

Here's a thought for those who think it won't take off - what would happen if you put a plane on stilts such that it's wheels were off the ground and fired up the engines?

a) The wheels would spin manically.
b) The plane would jolt forward and topple the stilts.

Unless you think a) is correct then there's no reason why a plane on a conveyor belt would not take off.

OK ignore the belt. If a plane just popped into existance in mid air 10m above the ground while stationary with its engines at full pelt it would fall to the ground.

 

[RandomBastard]

the plane would not accelerate because it is being acted on by two equal and oposite forces therefore no airflow therefore no lift and no take off.

The thrust from the engine pushing the plane forwards is counteracted by the ground it is moving along moving backwards, hence 0 forward momentum/speed/velocity in relation to the universe, no air movement, no lift, no takeoff

 

[Danya]

[19:50] <Socky|****> BUT the belt speeds up making just the wheels spin
[19:50] <Socky|****> not alowing it to create any foward motion

There's your error. The plane does not require wheels to create forward motion, if it did it would never be able to fly, you know with the wheels not moving and all.

The wheels turn because the plane is moving. If the plane is not moving then the wheels cannot be turning! Remember, wheels won't turn without something making them turn, and they don't get any power from the plane.

 

[Danya]

OK ignore the belt. If a plane just popped into existance in mid air 10m above the ground while stationary with its engines at full pelt it would fall to the ground.

Sure it would, because it's stationary. That's not what's being discussed though.

 

[Xgkkp]

the plane would not accelerate because it is being acted on by two equal and oposite forces therefore no airflow therefore no lift and no take off.

The thrust from the engine pushing the plane forwards is counteracted by the ground it is moving along moving backwards, hence 0 forward momentum/speed/velocity in relation to the universe, no air movement, no lift, no takeoff

Someone didn't feel like reading a thread!

 

[Danya]

the plane would not accelerate because it is being acted on by two equal and oposite forces therefore no airflow therefore no lift and no take off.

The thrust from the engine pushing the plane forwards is counteracted by the ground it is moving along moving backwards, hence 0 forward momentum/speed/velocity in relation to the universe, no air movement, no lift, no takeoff

The ground moving is not an equal force to the thrust of the engines, that's the point of having wheels.

 

[Wij]

the plane would not accelerate because it is being acted on by two equal and oposite forces therefore no airflow therefore no lift and no take off.

The thrust from the engine pushing the plane forwards is counteracted by the ground it is moving along moving backwards, hence 0 forward momentum/speed/velocity in relation to the universe, no air movement, no lift, no takeoff

YES - IT WOULD BE A PROBLEM *IF* THE WHeeLS HAD THEIR BRAKES ON !

*head/wall/bang*

I've also already explained that the plane COULD NOT be stationary as the question is stated. It's a logical contradiction.

CLOSE THE THREAD !!!

 

[Sockstuff]

If the plane is not moving then the wheels cannot be turning!

But what about the FUCKING BELT UNDER THE PLANE THAT IS MOVING AT 100mph BACKWARDS AND THE WHEELS MOVING 100MPH FOWARDS PWEIFO: HNKD GVILJHSDO:VSJIVKOPJdcvb

 

[Clown]

But WHAT IF THE ORLY OWL WENT IN THE ENGINE AND THE CONVEYOR BELT IS GOING BACKWARDS AND X^N MPH WILL THE PLANE FLY BACKWARDS??

 

[Wij]

But what about the FUCKING BELT UNDER THE PLANE THAT IS MOVING AT 100mph BACKWARDS AND THE WHEELS MOVING 100MPH FOWARDS PWEIFO: HNKD GVILJHSDO:VSJIVKOPJdcvb

Did you even read my post on the previous page ???

If you didn't then shut up.

If you did and still disagree then shut up.

 

[TdC]

CLOSE THE THREAD !!!

logic flaws make Wij's knickers twist

 

[Danya]

But what about the FUCKING BELT UNDER THE PLANE THAT IS MOVING AT 100mph BACKWARDS AND THE WHEELS MOVING 100MPH FOWARDS PWEIFO: HNKD GVILJHSDO:VSJIVKOPJdcvb

For god's sake man, NEVER go into aerospace design.

 

[Sockstuff]

Did you even read my post on the previous page ???

If you didn't then shut up.

If you did and still disagree then shut up.

I did, but it is incorrect.

 

[Danya]

But WHAT IF THE ORLY OWL WENT IN THE ENGINE AND THE CONVEYOR BELT IS GOING BACKWARDS AND X^N MPH WILL THE PLANE FLY BACKWARDS??

The end of the universe?

 

[Danya]

But what about the FUCKING BELT UNDER THE PLANE THAT IS MOVING AT 100mph BACKWARDS AND THE WHEELS MOVING 100MPH FOWARDS PWEIFO: HNKD GVILJHSDO:VSJIVKOPJdcvb

If the plane isn't moving, why is the belt travelling at 100 mph?

 

[TdC]

well yeah, because that owl is dead and prolly already in it's component atoms by now and if a plane were still to hit it something vastly wrong would be occuring I think.

 

[WPKenny]

I've just had a shit and a moment of clarity. These things often go together. Try and imagine this. You get a piece of elastic and attach it to a skateboard. Stretch the elastic and let it go. It will accelerate towards the tether.

Now reset the experiment only, put a large sheet of paper underneath. At the same time as you release the skateboard, pull the paper, as fast as you like in the opposite direction. Do you think the skateboard (assuming zero friction between the wheel's ball bearings i.e. perfect conditions) will travel any slower the second time around?

If you think it will affect it's speed, chances are you're saying "no the plane won't take off."

Now go try it....

 

[TdC]

If the plane isn't moving, why is the belt travelling at 100 mph?

there is no belt</matrix>

 

[Sockstuff]

If the plane isn't moving, why is the belt travelling at 100 mph?

Because the thrust of the engine is trying to roll the plane foward at 100mph, so the belt moves backwards at 100mpg = no foward motion of the plane. just wheels and belt spinning

 

[Danya]

But the belt moves at the speed of the plane, not at some made up 100 mph number.

 

[Sockstuff]

I've just had a shit and a moment of clarity. These things often go together. Try and imagine this. You get a piece of elastic and attach it to a skateboard. Stretch the elastic and let it go. It will accelerate towards the tether.

Now reset the experiment only, put a large sheet of paper underneath. At the same time as you release the skateboard, pull the paper, as fast as you like in the opposite direction. Do you think the skateboard (assuming zero friction between the wheel's ball bearings i.e. perfect conditions) will travel any slower the second time around?

If you think it will affect it's speed, chances are you're saying "no the plane won't take off."

Now go try it....

This is throwing a staionary object that the plane can be tied to into the mix.