Will the plane take off?? Finally going to be answered.***

[Chevillac 5,000+ posts]

you havent explained it, and dev, i think you worded it a bit awkwardly...
the wheels are moving at a rotational speed.

the plane is moving at a velocity (note, velocity is defined by having a speed, and direction)

increased rotational speed does not equal increased velocity. the airplane is able to increase velocity inproportionatly to the wheels rotational speed because of the way force is applied.

which part?

 

[hoss 5,000+ posts]

this whole argument about more thrust after the fact is irrelavant.


the key word in the question was "MATCHES". if the belt MATCHES the jet, the jet will not be going forward. so stop arguing a null point. sure the jet most likely could overcome the belt. but thats not the question.

the belt can match the speed of the jet all it wants, it still isnt applying force to the jet, so the jet continues to accelerate

if this was a car, then you would be correct. or if the question at hand was would the plane take off if something was counteracting the airplanes force, then it would be a different experiment...

 

[hoss 5,000+ posts]

which part?

about air speed and ground speed. im just guessing, but i think you meant the speed at which the tires are spinning, vs the speed at which the plane is traveling.

 

[IamDeMan 5,000+ posts]

OK lets say the plane started on solid non moving ground. It accelerated to 50MPH and maintained this speed with no increase in propulsion and ran across a 100ft long treadmill doing 50MPH in reverse. Would the plane just slow down until stationary on the moving treadmill when it reached it?

It may slow down by the slightest fraction due to increased friction at the wheels but it certainly wouldn't stop, it would continue on to the end.

 

[IamDeMan 5,000+ posts]

i dont know why this is so hard to understand.
they only air that will be moving is what the propeller is moving, but that is not the air creates the lift, its the air that travels under the wings that does it. there will be NO air traveling under the wings.

It will be moving forward numbnuts. All the way to the end of this treadmill. The treadmill is applyint NO FORCE to the plane.

 

[Chevillac 5,000+ posts]

this whole argument about more thrust after the fact is irrelavant.


the key word in the question was "MATCHES". if the belt MATCHES the jet, the jet will not be going forward. so stop arguing a null point. sure the jet most likely could overcome the belt. but thats not the question.

but this is exactly the point, the belt cant stop the plane from moving. did you watch any of the videos? They explain this and use model planes on treadmills. They even make the treadmill go faster than the plane can go and the plane still moves forward at the same speed.

i dont know why this is so hard to understand.
they only air that will be moving is what the propeller is moving, but that is not the air creates the lift, its the air that travels under the wings that does it. there will be NO air traveling under the wings.

it was rhetorical, yes air speed and ground speed are different.

http://www.aerospaceweb.org/question/instruments/q0251.shtml

Can a plane take off on ice? (if you can keep it straight)

no, its not going to take as much force as you think, the ONLY force being applied to the airplane itself, is friction.

//content.invisioncic.com/y282845/emoticons/word.gif.64b12e39f936af3b4fff38a1c0bd0244.gif

and not enough.

 

[Chevillac 5,000+ posts]

about air speed and ground speed. im just guessing, but i think you meant the speed at which the tires are spinning, vs the speed at which the plane is traveling.

//content.invisioncic.com/y282845/emoticons/word.gif.64b12e39f936af3b4fff38a1c0bd0244.gif

and im starting to think req and 04 are just arguing the other side, just because.

 

[04_edge 10+ year member]

i think i see now.

 

[req 5,000+ posts]

i see what you are saying.

you are saying the wheels will speed up to accomadate for the movement of the treadmill but the plane will still move forward at X speed.

yuh i get it.

sorry about that. i feel sheepish.

 

[04_edge 10+ year member]

x2

i get it now.

 

[IamDeMan 5,000+ posts]

i see what you are saying.

you are saying the wheels will speed up to accomadate for the movement of the treadmill but the plane will still move forward at X speed.

yuh i get it.

sorry about that. i feel sheepish.

No problem, I made the same mistake in the very beginning. I just didn't need a sledgehammer to tell me I was wrong.

 

[T3mpest 10+ year member]

In case anyone is still lost think of it like this, first imagine a car.

A car moves because the wheels spin. They spin around, push against the ground and the car moves forward. If you put a car on a treadmill going the same speed in the opposite direction the car will not move forward. The treadmill pushes one way the wheels push another and the car stands still. That should be fairly apparent and intuitive.

Now let's add 1 thing to that car, lets make it like the batmobile. The force that now moves the car isn't the wheels. We have strapped a rocket to the back. The rocket propels air backwards, which pushes the car forwards. Even if the wheels were not moving at all the car would still move, assuming the rocket could overcome the friction of the wheels grinding on the ground. Now when we put the rocket powered car on a treadmill the wheels forces are still cancelled out. The wheels wont' push the car forward, but the force of the air being expelled by the rocket WILL move the car forward. This is how a plane moves. The wheels arent' what physically drives a plane down the runway, it's the force of the fans displacing air. So despite the fact that the treadmill cancels out the wheels propulsion, the plane will stil go forward. The treadmill speed is irrelavent, unless the thing can spin so fast that the the frictional forces on the wheels can counter the tremendous force of the air being displaced by the engines.

As long as the plane can move forward there is air under the wings moving, hence we get lift....

Overall what you need to realize is that the wheels spinning in a byproduct of the moving plane, not the reason the plane moves, hence the treadmill can counter the wheels all it wants, the plane will still go forward.

 

[IamDeMan 5,000+ posts]

Batmobiles are teh cool.

 

[IamDeMan 5,000+ posts]

Lame. I don't need a physics book to do that.

Besides my thread today fully explains it all.