Flint, this thread has nothing to do with global warming. You have also never proved anything in your life

>The lift force which an aircraft needs to take off is as a result of air flowing over the wings.

Right, so the plane needs to move forward relative to an observer on the ground and take off when their is sufficient airflow over the wings. We get that.

>If an aircraft is on a conveyor belt which means it is stationary with respect to an observer standing watching on a patch of grass next to the conveyor belt then the aircraft is also stationary with respect to the air around it. The air will not flow over the wings and therefore there will be no lift and no take off.

Wrong. The conveyor belt doesn't effect the plane because the thrust from the engines isn't being transferred to the ground. What do planes engines push against? It's not the ground. At 35,000 ft there's no ground for the planes engines to push against. Therefor even though the conveyor is moving at the exact opposite speed of the plane, the plane will still move forward relative to the observer because it doesn't rely on it's tires to propel it forward.

Read this:

http://mouser.org/log/archives/2006/02/001003.html

And this one is even better:

http://www.illuminatingscience.org/plane-on-a-conveyor-belt/

>The question states that the wheel rolling speed will never be more than or less than the conveyer belt speed, and so the plane will not move anywhere.

I get what you're saying. As the plane accelerates the wheels will move faster. The conveyor moves in the opposite direction the same as the wheel speed. This means that at any given point the wheels and conveyor would be moving twice as fast as the plane is moving forward. This is all irrelevant because the conveyor still has no ability to stop the plane from accelerating since the plane is putting a force against the air and not the conveyor. Assuming the wheels and conveyor belt don't explode from spinning at twice the speed of the plane the plane will take off like normal.

>ok, now at the very beginning. the conveyor is turned on, lets say it moves 20mph; the pilot turns on the engine, very low, so that the wheels are going 20mph. when the wheels and the conveyor are both going 20mph, the airplane isnt moving. its stationary. because the rate the wheels are turning is canceled by the equal rate of the conveyor. now no matter how much you speed this up, even if the wheels are turning at the speed of light, the plane will be stationary if the conveyor is moving at the same speed as the wheels.

Erm not quite. This site explains what it would take from a conveyor to keep a 747 motionless during takeoff. http://thelimitingreactant.blogspot.com/2008/09/riddle-airplane-on-treadmil.html
It takes A LOT more then a conveyor matching the planes speed to generate enough friction to keep the plane from moving forward and taking off.

if the wheels spin in a said direction at N mph.. and in an opposite direction in also N mph.. then the wheels will be in equilibrium and therefore will not move..

imagine your in a car.. you put your foot on the brake and press the accelerator.. your wheels dont movee forward, because the force pushing the car forward is equal to the brakes...

the same applies to the plane theory.. therefore the whells are stationary so the plane does not move..

enough of that arguement

now.. with the air arguement.. imagine your standing still on a non windy day.. do you feel the wind on your face? no you do not.

now.. if you start running in a direction, the faster you go the more air friction you create as you are passing through air particles faster than they can move out the way, hence you create a bigger drag.. this is how planes work.. they go fast in a said direction, creating huge amounts of drag and instead of slowing them down, they use aerodynamics to create a bigger pressure on top of the wings, therefore more of the wind goes below the wings as it has less pressure here and pushes the plane up..

therefore, if a plane is stationary and not moving, there is no chance that it could take off..

oh and on the aerodynamics thing, its also how racing cars have such good grip.. they use the opposite to planes, and create higher pressure below the car so that more air flows above the car, forcing it down onto the road.. equaling better grip

if anyone thinks im talking crap then please correct me but this is what ive learnt from around the place and im currently studying physics A-level at college..

[Humidity]>imagine your in a car.. you put your foot on the brake and press the accelerator.. your wheels dont movee forward, because the force pushing the car forward is equal to the brakes...

the same applies to the plane theory.. therefore the whells are stationary so the plane does not move..

I say this nicely but you are completely wrong. Rather then repeating myself again just think about this. You are saying that a plane relies on it's friction with the ground to move forward. If a plane needed it's wheels to push against the ground to move in a forward direction then at 35000 ft where there is no ground the engines would not be moving the plane.

Anyways back to what avo was saying. . .

[Avo]>ok, now at the very beginning. the conveyor is turned on, lets say it moves 20mph; the pilot turns on the engine, very low, so that the wheels are going 20mph. when the wheels and the conveyor are both going 20mph, the airplane isnt moving. its stationary. because the rate the wheels are turning is canceled by the equal rate of the conveyor. now no matter how much you speed this up, even if the wheels are turning at the speed of light, the plane will be stationary if the conveyor is moving at the same speed as the wheels.

Ok I concede that the above is right up to a certain thrust from the engine.

First all the coefficients of friction I'm using come from this page: http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm

And some info about a 747-100 from here: http://www.airliners.net/aircraft-data/stats.main?id=97
Max takeoff weight: 750,000lb
Max thrust(all 4 engines combined): 187,800lb
Tire radius: 4ft
Number of tires: 16
Hard rubber on cement coefficient: 0.01 (assuming for simplicity the conveyor has the same coefficient as the runway normally would)

Rolling friction of a 747:
F  in Newtons = number of tires * Coefficient of Hard rubber on Cement * weight in kg per tire * 9.81
16 * 0.01 * (85,184.6471/16) * 9.81 = 8356 n or 1878.5lb

This number is the maximum amount of force the conveyor at any speed - matching the wheels speed or not- could exert against the plane.

This means the 747 would be held stationary by the conveyor belt like you said it would until it's engines exerted more then about 1 ton of thrust. Remember the 747 can exert 187,000lb of thrust.

"Ok I concede that the above is right up to a certain thrust from the engine."

correct. BUT when the 747 becomes no longer stationary, the wheels are moving faster then the conveyor belt; right? do you understand that? now the original post in this thread asks, if the plane can take off if the conveyor belt matches the speed of the wheels. so he's asking if the plane can take off before the engine's thrust makes the wheels travel faster then the conveyor.

<Pixie> A10..this question is different to the questions you're looking at elsewhere. In this question, the conveyer belt matches the speed of the WHEELS not the speed of the 747.

The conveyor can move as fast as it wants- matching the speed of the wheels or doubling the speed of the wheels. The max force against the plane from the conveyor is still about 2000lb and can only hold the plane back as long as the plane never exerts a thrust more then 2000lb or about 1% of it's max thrust.

<Avo> correct. BUT when the 747 becomes no longer stationary, the wheels are moving faster then the conveyor belt; right?

Not quite.The wheels are now going faster then the plane. The conveyor matches the speed of the wheels. The wheels and the conveyor are now going the speed they were when the plane was stationary on the conveyor plus the speed of the plane relative to the observer.

<Avo continued> do you understand that? now the original post in this thread asks, if the plane can take off if the conveyor belt matches the speed of the wheels.

The conveyor matches the speed of the wheels even when the plane stops being stationary. The wheels and conveyor just move at the speed of the plane plus the speed they were going previously. It's irrelevant though because the conveyor can never push against the plane more then about 2klb.

SO a 747 on a conveyor that PERFECTLY matches the speed of the WHEELS will still move forward relative to the ground and take off and the wheels and the conveyor will still be matched in speed.

<Avo>so he's asking if the plane can take off before the engine's thrust makes the wheels travel faster then the conveyor

Lol. You're thinking that once the plane moves forward the conveyor and the wheels aren't matched in speed. The wheels turn faster as the plane accelerates. The wheels never travel faster then the conveyor because as the wheels increase in speed the conveyor increases as well.

The conveyor increases to match the speed of the wheels but they still never exert a force greater then about 2klb against the plane. They don't stop the plane from moving but the wheel and the conveyor are still moving at the same speed.

>no way you're this stupid; im done feeding the troll.

That must be your way of admitting you're wrong.

/me welds a metal sign that reads 'BUSTED' and throws it on the table for everyone to see.