Riddle Me This.........

[Casper]

Originally Posted by JAJH

I'm sorry Shane, I just don't think you are looking at it relatively. The thrust will move the plane forward and cause the wheels to spin, the conveyor will react at the same speed in the opposite direction. The forward motion of the thrust make the wheels spin but is then negated by the conveyor, it will remain stationary. If you stand next to it, it will NOT move.

but you said the sidewinder on the skateboard would go forward because of its thrust.. whats the difference?

If you accept that the rocket will go forward than the plane is the identical principle.

[JAJH]

Originally Posted by Casper

but you said the sidewinder on the skateboard would go forward because of its thrust.. whats the difference?

If you accept that the rocket will go forward than the plane is the identical principle.

The difference is the rocket is relying on thrust only, not like a plane that requires forward speed which in turns creates the optimal lift created by air rushing over its' wings.

[Ghiadude]

[QUOTE=DOC]ok the wheels are doing 10K now the treadmill going the other way at 10k, so how does the plane move forward ?

:[/QUOTE

read my post again you missed alot

[Captain Stubing]

Originally Posted by Casper

No, it wont hold the plane in place at all. The only wiay it could hold the plane in place if if the plane was transmitting it forward thrust through the wheels.. like a car. Then it would be held in place. Since a plane creats thrust via a propellor (or jet or rocket) the convayor belt does not absorb this thrust. The plane will move forward as per normal.

But the plane speed , which is transmitted initially to the conveyor by rotation of the wheels, is countermanded by the reverse action of the conveyor belt, which means the plane doesn't get to accelerate to achieve lift.

[Ghiadude]

Originally Posted by JAJH

The difference is the rocket is relying on thrust only, not like a plane that requires forward speed which in turns creates the optimal lift created by air rushing over its' wings.

no a rocket and a plane rely on thrust for forward motion

[Casper]

Originally Posted by JAJH

The difference is the rocket is relying on thrust only, not like a plane that requires forward speed which in turns creates the optimal lift created by air rushing over its' wings.

thrust creates forward speed.. which creates lift. Same principle. Once you have thrust you have forward speed. Once you have forward speed you have lift.

[Ghiadude]

Originally Posted by swanny

But the plane speed , which is transmitted initially by rotation of the wheels, is countermanded by the reverse action of the conveyor belt, which means the plane doesn't get to accelerate to achieve lift.

no at no point is it transmitted by the wheels... planes roll purely because of the thrust of the engine...

[Casper]

Originally Posted by swanny

But the plane speed , which is transmitted initially by rotation of the wheels, is countermanded by the reverse action of the conveyor belt, which means the plane doesn't get to accelerate to achieve lift.

no, the planes forward thrust is not through the wheels. The wheels go around as a concequence of it moving forward but do not propel it forward. They simply hold it off the ground as it does so.

[42.57lb]

Ok, this is it, the be all and end all of this argument.

Charlie, Casper, Malakai, please, consider this. Everything you have said about the wheels yeah, can you lot an dI agree that the wheels contact the ground? yeah. Ok now ca we also agree that the wheels contacting the ground create friction? yeah. No, take rolling resistance ok, you're drving you XR8, GT whatever, you're going 100kmp/h ok. Now, you take your foot of the accelerator, take the car out of gear, so you're free wheeling. You stop right. Why? the answer is rolling resistance. if you disagree then please tell me why.

OK

NOW: the treadmill, acceleratate at the same RATE as the engine thrust such that if the thrust provided has enough POWER to propel the aircraft and 200 kph then the ROLLING RESISTANCE increases to teh same, NEGATING the thrust, the over all POWER is 0.

ERGO, the craft does not accelerate, the wind DOES NOT rush over the wings, the lift is not created and the palne does not take off. Theh SIMPLE reason for this is that the THRUST FORCE is exactly the same as teh FRICTION (or drag) and therefore there is no net force so taht there can be no ACCELERATION and the plane cannot be anything other than stationary.

THE ONLY way that it can fly is if the frictional forces are lower than the thrust forces and that would mean that the "runway" is not moving in the opposite direction at the same rate as the thrust of the engines is proppelling the craft.

[JAJH]

Originally Posted by tx3dude

no a rocket and a plane rely on thrust for forward motion

Yes agreed, they do both rely on thrust, but in this scenario there is no forward motion of the plane to create lift. I wouldn't have thought this was such a difficult concept to grasp.

[Ghiadude]

Originally Posted by 42.57lb

NOW: the treadmill, acceleratate at the same RATE as the engine thrust such that if the thrust provided has enough POWER to propel the aircraft and 200 kph then the ROLLING RESISTANCE increases to teh same, NEGATING the thrust, the over all POWER is 0.

E

if you follow that school of thought aviation isnt happening right now... because the rolling resistance would stop planes taking off... capish??

[Casper]

Originally Posted by 42.57lb

Ok, this is it, the be all and end all of this argument.

Charlie, Casper, Malakai, please, consider this. Everything you have said about the wheels yeah, can you lot an dI agree that the wheels contact the ground? yeah. Ok now ca we also agree that the wheels contacting the ground create friction? yeah. No, take rolling resistance ok, you're drving you XR8, GT whatever, you're going 100kmp/h ok. Now, you take your foot of the accelerator, take the car out of gear, so you're free wheeling. You stop right. Why? the answer is rolling resistance. if you disagree then please tell me why.

OK

NOW: the treadmill, acceleratate at the same RATE as the engine thrust such that if the thrust provided has enough POWER to propel the aircraft and 200 kph then the ROLLING RESISTANCE increases to teh same, NEGATING the thrust, the over all POWER is 0.

ERGO, the craft does not accelerate, the wind DOES NOT rush over the wings, the lift is not created and the palne does not take off. Theh SIMPLE reason for this is that the THRUST FORCE is exactly the same as teh FRICTION (or drag) and therefore there is no net force so taht there can be no ACCELERATION and the plane cannot be anything other than stationary.

THE ONLY way that it can fly is if the frictional forces are lower than the thrust forces and that would mean that the "runway" is not moving in the opposite direction at the same rate as the thrust of the engines is proppelling the craft.

This would be correct except the convayor moves at the same speed as the planes forward motion. It is rigged to travel in reverse at the same "speed" as the plane is moving forward. It cannot counteract the planes thrust. Not unless it can change the density of air around the plane.

[Captain Stubing]

I didn't meant forward thrust is from the wheels. The conveyor belt matches the plane speed, which, from a standstill, obviously is from wheel speed.

The wheels are there to allow the plane to get up to a speed where the air will provide lift.

If it was a seaplane, it would be pontoons.

[Casper]

Originally Posted by JAJH

Yes agreed, they do both rely on thrust, but in this scenario there is no forward motion of the plane to create lift. I wouldn't have thought this was such a difficult concept to grasp.

so the rocket has forward motion from thrust.. but the plane does not have forward motion from the same thrust?

[Steffo]

Ok, according to some of the theories here, the plane wouldn't have the ability to generate the sufficient speed needed to create lift on the conveyor, so it wouldn't take off....

Now, I'm no expert, but how do the Harrier Jump Jets and Yakolev YAK-141 Freestyle's work?



Do these not lift vertically with the engines on the bottom, then engage the rear engines while disengaging those (ie: hover, power the rear ones up, then engage them and disengage the bottom ones...)

So that means, according to some of the theories here, a Jump Jet or YAK-141 should fall to the ground because they're not going fast enough to stay airborne?

I agree with Casper, the plane would take off from the conveyor, the wheels simply spinning at twice the speed the plane and/or conveyor is moving at.

[XA Coupsta]

Originally Posted by 42.57lb

Ok, this is it, the be all and end all of this argument.

1. Why is your argument the be all and end all? This argument was ended about 9 pages ago.

2. If your argument is indeed going to be the end all and be all - it should be a lot better argument than the one just supplied.


Forget the wheels guys!!! They have nothing to do with it except throw logic into chaos - and its working with some!!!!!

[Captain Stubing]

Originally Posted by Casper

....... It cannot counteract the planes thrust. Not unless it can change the density of air around the plane.

The thrust is from the forward movement of the wings through the air.

The conveyor belt stops this from the start, when the plane starts to go.

[Ghiadude]

Originally Posted by JAJH

Yes agreed, they do both rely on thrust, but in this scenario there is no forward motion of the plane to create lift. I wouldn't have thought this was such a difficult concept to grasp.

the two big rolls royce engines on each side of a jumbo create thrust... enough actually to accelerate a jumbo to take off speed and well beyond. the plane is still pushing against the air ...this causes plane to move forward as it moves forward the wheels will have to spin faster and faster but the plane keeps moving towards the end of treadmill regardless of weahter the wheels are spinning or at what speed

[JAJH]

Originally Posted by Casper

so the rocket has forward motion from thrust.. but the plane does not have forward motion from the same thrust?

That's right, they both do have thrust, but the aerodynamics involved in getting a plane off the ground are somewhat different to a rocket. As I said before, a rocket doesn't require speed and lift to become airborne, just thrust.

[Casper]

Originally Posted by swanny

The thrust is from the forward movement of the wings through the air.

The conveyor belt stops this from the start, when the plane starts to go.

no, the thrust is from the engine.. the prop or the jet. The forward movement of the wings through the air is a concequense of this thrust. Action and reaction.
Saying that something that relies totally on thrust will take off yet something that relies on thrust and has wings attached wont take off is argueing against yourself.

[42.57lb]

Originally Posted by XA Coupsta

1. Why is your argument the be all and end all? This argument was ended about 9 pages ago.

2. If your argument is indeed going to be the end all and be all - it should be a lot better argument than the one just supplied.


Forget the wheels guys!!! They have nothing to do with it except throw logic into chaos - and its working with some!!!!!

Sorry buddy, the wheels are an integral part of this energy system, they are what is connection physically to the tarmac, therefore they are what produces the friction. If you said "and there is NO friction between a) the wheels and the tarmac and b) the wind and the body of the aircraft I would have abosolutely 0 problem agreeing that the plane would take off. I'd say "well done guys, hat off to you" BUT unfortunately one of teh specifications of teh problem is that the wheels ARE ont he tarmac and as such they DO produce friction.

If it was over 9 pages ago then why are all us dumb asses here?

[XA Coupsta]

Originally Posted by swanny

The thrust is from the forward movement of the wings through the air.

No man. The thrust is supplied by the engines.

[flappist]

JAJH & 42lb you are both missing the plot completely...

The thrust does NOT cause the wheels to turn it causes the plane to move relative to the air.

The only reason the wheels turn is that there is a difference is speed between the surface that the wheels are in contact and the axles of the wheels.

It does not matter what this difference is.....

Imagine no wheels, just super slippery oil and skids, doesn't matter how fast the ground is moving the plane is slipping over the top of it.

[Ghiadude]

Originally Posted by DOC

ok the wheels are doing 10K now the treadmill going the other way at 10k, so how does the plane move forward ?

:

you said yourself a plane moving forward(relative to the ground) is doing 10kph...

[42.57lb]

Originally Posted by Casper

no, the thrust is from the engine.. the prop or the jet. The forward movement of the wings through the air is a concequense of this thrust. Action and reaction.
Saying that something that relies totally on thrust will take off yet something that relies on thrust and has wings attached wont take off is argueing against yourself.

Dude, I can so see where you are coming from. AND if the probelm stated that there was a wall behind the jet, I would agree entirely with you, just like the aircraft carriers, however there is no wall. The trust a rocket has is 1) against gravity, it does not rely on lift from wings, which is why they point rockets straight into the air.

Also, rockets don't have wheels to give them friction against the earth.

If the rocket was only as powerful as the force of gravity, it would go anywhere, see what I mean?

[Casper]

Originally Posted by JAJH

That's right, they both do have thrust, but the aerodynamics involved in getting a plane off the ground are somewhat different to a rocket. As I said before, a rocket doesn't require speed and lift to become airborne, just thrust.

A rocket does require speed and lift to become airborne. Thrust simply provides the speed which, in turn, provides lift. Rockets have control surfaces and lift surfaces too. Because the immense speed created by the rocket is to high these control surfaces need only be very small... but they are there.

[Dave_au]

This thread still going!

Answer from an aerospace engineer:

[XA Coupsta]

Originally Posted by 42.57lb

Sorry buddy, the wheels are an integral part of this energy system, they are what is connection physically to the tarmac, therefore they are what produces the friction. If you said "and there is NO friction between a) the wheels and the tarmac and b) the wind and the body of the aircraft I would have abosolutely 0 problem agreeing that the plane would take off. I'd say "well done guys, hat off to you" BUT unfortunately one of teh specifications of teh problem is that the wheels ARE ont he tarmac and as such they DO produce friction.

If it was over 9 pages ago then why are all us dumb asses here?

Ahh hell - we are all here coz we like a good argument!

Hey no harm intended with any of this.

But the wheels ARE NOT an integral part of the energy equation at all im afraid man. So what if they attach the aircraft to the tarmac - its not them that is gonna have SFA to do with it taking off.

They are like an inate object in this entire picture. They (and the rolling conveyor thing) have been placed in the hypothetical situation to confuse it and throw you 'off the scent' of answering it correctly.

[Casper]

Originally Posted by 42.57lb

Dude, I can so see where you are coming from. AND if the probelm stated that there was a wall behind the jet, I would agree entirely with you, just like the aircraft carriers, however there is no wall.

If this was the case than the X Plane jets dropped mid air by the US Airforce and then fired up in freefall wouldnt accellerate as there is no wall behind them at 30,000feet. Same as a 747 would be able to move off a normal runway as there is no wall behind them either.

[42.57lb]

I think everyone has a fundamental mis-understading

THRUST provides force - once one force is greater than another accleration occurs, once the forces are equal no acceleration occurs, so if you are travelling at a constant 100kph in your car it's because there is no net thrust or power. The rolling resistance of your tyres is equal to the thrust produced by your engine so you maintain your speed. The reason you slow down when you take your foot off the accelerator is because your rolling resistance is HIGHER than you driving thrust so you take your foot off the accelerator and you slow down right.

SAME applies while the plane is on the ground