Steve
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quote:
Originally posted by Steve
Think of it this way, push a toy car along a treadmill your arm will still move at the same rate and use the same amount of force to get it to the end as it would if the car were on a solid surface
think about this david, this gives a perfect explanation as to why it would move, its because the force is being applied by a 3rd party, not related to the force acting in the opposite direction
your arm is acting like the thrust
[Edited on 23-05-2006 by Steve]
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Ally
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Yes
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gianluigi
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but would it move enough to generate any lift?
movement will be little, and as it moves the conveyor belt will speed up, and therefore the plan will stop per say
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bradfincham
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See im in 2 minds about this - hence why i posted this and already 2 pages long.
There is 0 knots relative ground speed, so this means there is 0 air flow over the wings. For a plane to take off there needs to be lift. Lift is created by a high pressure of air under the wing and a low pressure of air ontop of the wing.
So this means that the plane wont take off.
However the planes engines are at full thrust, all the plane needs is a little head wind, which will create the airflow over the wings, create lift and the plane will take off.
Keep arguing 
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Paul_J
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quote:
Originally posted by Cybermonkey
why would the plane move??? it sitting on a moving solid surface which is matching its speed. if the "conveyor" trick works, why dont they use it to launch off aircraft carriers and the such??
because you clearly have got the wrong end of the stick.
It doesn't say the conveyer will be applying the exact opposite force of the planes thrust - it says it'll go backwards as fast as the plane moves.
so when plane is stationary, the belt is stationary. Engines at full thrust will move it forward as steve's example explains. As it moves forward the belt will go backwards, however this will not hold or push the plane backwards but spin the wheels underneathe the plane.
the plane will continue accelerating along until it reaches a speed that there is enough lift under the wings and takes off.
This would slow the acceleration of the plane down so would require a much longer take off distance than a normal runway - this is why no one would use these on air craft carries lol 
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Paul_J
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Brad if no wind and the plane has no movement it won't take off simple as.
the question is - if the conveyor belt is not HOLDING the plane at 0 knots, which using steve's example suggests it would not be. the plane will accelerate abiet slowly - and thus eventually reach a taking off speed.
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Jules S
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The best way ive heard to explain this is as follows:-
Imagine a plane with no engines on a conveyor belt.
The conveyor belt is running at say a nominal 1000rpm, there is no friction in the wheels therefore the plane is stationary.
Are we following?
Next we need to apply a force to the plane...
Does anybody here want to claim that they couldnt push the plane forward even if the conveyor belt compensates for forward movement?
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Steve
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quote:
Originally posted by Cybermonkey
why would the plane move??? it sitting on a moving solid surface which is matching its speed. if the "conveyor" trick works, why dont they use it to launch off aircraft carriers and the such??
because the plane still needs the samel length conveyor belt to take off as a normal runway
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Steve
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will people please read my exmaple and think about it
Think of it this way, push a toy car along a treadmill your arm will still move at the same rate and use the same amount of force to get it to the end as it would if the car were on a solid surface
[Edited on 23-05-2006 by Steve]
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Bram
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quote:
Originally posted by Cybermonkey
no steven NO NO NO. there is no airflow over the wings, the aircraft is not moving through the air no matter how much thrust is pushing the aircraft forward, the aircraft will remain in the same place, upon the conveyor, with its wheels spinning round frantically. no lift forces are being generated since air flow over the wings is 0 KNOTS. you of all people should know this.
He speaks the truth!
Its all in the wording of the question!
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Paul_J
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quote:
Originally posted by Bram
Its all in the wording of the question!
exactly - it's brads poor wording and vauge question different people are interperting it different ways, and in a sense everyone is correct depending on what they believe the question means.
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bradfincham
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Paul - yeh thats what i posted on another forum,
Which is why i feel it would take off 
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bradfincham
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Basically the wheels would rotate at twice the speed, to counteract the conveyor belt
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Steve
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yep
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bradfincham
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But in sense of the way cyber is reading it then a little head wind and it would take off
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Hammer
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quote:
Originally posted by Paul_J
quote:
Originally posted by Bram
Its all in the wording of the question!
exactly - it's brads poor wording and vauge question different people are interperting it different ways, and in a sense everyone is correct depending on what they believe the question means.
theres nothing vague about it, the plane takes off as an airplane is not propelled by its wheels, they're free rolling 
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Cosmo
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the plane would more or less be stationary, therefore no airflow over the wings, therefore no takeoff.
It doesnt matter that the wheels arent powered, if the plane hasnt got forward movement it wont be taking off.
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Lawrah
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Cant people just use google?
http://mouser.org/log/archives/2006/02/001003.html
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Steve
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if the force pushng the plane is from a fixed third party object then the conveyor belt has no effect, just like it has no effect when you push the toy car along the tread mill, your arm is the fixed third party force, the jet engines and the air its pushing against is also a fixed third party force
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Steve
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quote:
Originally posted by Steve
will people please read my exmaple and think about it
Think of it this way, push a toy car along a treadmill your arm will still move at the same rate and use the same amount of force to get it to the end as it would if the car were on a solid surface
[Edited on 23-05-2006 by Steve]
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JadeM
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Is there an answer to this or is it just a total headfuck
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bradfincham
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quote:
Originally posted by Cosmo
the plane would more or less be stationary, therefore no airflow over the wings, therefore no takeoff.
It doesnt matter that the wheels arent powered, if the plane hasnt got forward movement it wont be taking off.
But it does have forward movement, as the wheels arent driven
Paul has explained it best,
as from a start the wheels will turn on the plane, the engines will be at full thrust, the conveyor will go the opposite way and the wheels on the plane will go twice as fast as there counteracting the conveyor belt
the thrust will still be provided and the plane accelerating, just the wheels will be going mentally fast underneath to counteract the runway
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Steve
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iv explained it the fucking best with my example 
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bradfincham
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Yeh totally but noones reading the example as its got a toy car!
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Steve
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exactly the same principle though 
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