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

[LTDHO]

Casper, I have seen the light.

The plane would take off as the thrust from the engines would still propell the plane, the conveyer would not hold it still.

Now I know this I will delete my subscription!!

[EA2BA]

well after a fresh think this morning, yes the plane does take off due to thrust, the wheels and the conveyor may be going 100 times the speed of light in opposite directions, but the plane will move forward, it will create lift, it will take off, just like a jet car in a dyno would jump off the dyno, even if the dyno rollers were spinning.

[cArSiK]

Originally Posted by Casper

same speed it does every other time it takes off.

Ok , im still trying to get my head around this:

Lets say a Police Officer (in victoria) is infront of the plane & conveyer , just before it lifts off what speed would his radar tell him the plane was travelling at?

Now Lets Say the Second the plane lifted off the ground , and he measured the speed once again what speed would it be traveling at from his point of view?

This means , within the space of a second , the plane has picked up 200+ KMH to keep airborn?

[Charliewool]

Ohhhhhhhh PLEASE, NOT another day of this!! :

[cArSiK]

Ok Casper has just explained it to me in very simple terms and the plane will take off.

[Casper]

Yay! ....

[SunDrifter]

Is this thread still going!

Here's the definitave answer for you all. Its a Loaded question!

It all depends on how you read the question and how you choose to interpret it. I think we can all agree that in a real world scenario, that plane would take off. However if you choose to agree with some magical fairy land physics that are assumed in the question, I put it to you that the plane won't go anywhere.

Your all right! Congratz. The sad fact is that your all wrong too! :p

[The Monty]

Originally Posted by SunDrifter

Is this thread still going!

Here's the definitave answer for you all. Its a Loaded question!

It all depends on how you read the question and how you choose to interpret it. I think we can all agree that in a real world scenario, that plane would take off. However if you choose to agree with some magical fairy land physics that are assumed in the question, I put it to you that the plane won't go anywhere.

Your all right! Congratz. The sad fact is that your all wrong too! :p

I 100% agree that it is both correct and wrong both ways. I think there needs to be more information in the actual question to be able to justify the correct answer.

well im glad it's over your all driving me mad

[42.57lb]

woohoo!!!!

[Black XR6]

Well, I think youve all got rocks in your heads. The plane would not take off under any circumstances. If the conveyor belt could keep up with the forward motion of the plane, ie the speed the wheels are going. There is no way the plane would take off.

The plane, any plain, needs air passing over and under the wings for it to get liftoff. It has nothing to do with thrust. Thrust is just what propels it forward, this is counteracted by the movement of the conveyor belt. Thus the plain remains stationary. The plain can not scientifically take off.

In the skateboard and elephant analogy this is a failed comparrison. The guy on the skateboard is on the conveyor, the elephant is on terra firma. The elephant is not goverened by the tredmill and will walk off. The treadmill couldnt possibly keep up with this movement. So the elephant is the thrust and is attached to the ground via its legs. The aircraft on the other hand is the skateboard guy, the skateboard and the engine. All sitting on the conveyor. Thats the difference.

At no time could the plane take off under these circumstances as it is not generating the lift required via the low pressure zone above the wing. Without this, the engines could fire at whatever power they want and the plane will not take off. I compare this to a plane with no wings. No matter how fast the engines go, it wont take off and fly. Atleast not whilst just sitting on a runway and not pointing straight at the ground. The conveyor belt negates the effect of the wings.

[Charliewool]

Originally Posted by Black XR6

Well, I think youve all got rocks in your heads. The plane would not take off under any circumstances. If the conveyor belt could keep up with the forward motion of the plane, ie the speed the wheels are going. There is no way the plane would take off.

The plane, any plain, needs air passing over and under the wings for it to get liftoff. It has nothing to do with thrust. Thrust is just what propels it forward, this is counteracted by the movement of the conveyor belt. Thus the plain remains stationary. The plain can not scientifically take off.

In the skateboard and elephant analogy this is a failed comparrison. The guy on the skateboard is on the conveyor, the elephant is on terra firma. The elephant is not goverened by the tredmill and will walk off. The treadmill couldnt possibly keep up with this movement. So the elephant is the thrust and is attached to the ground via its legs. The aircraft on the other hand is the skateboard guy, the skateboard and the engine. All sitting on the conveyor. Thats the difference.

At no time could the plane take off under these circumstances as it is not generating the lift required via the low pressure zone above the wing. Without this, the engines could fire at whatever power they want and the plane will not take off. I compare this to a plane with no wings. No matter how fast the engines go, it wont take off and fly. Atleast not whilst just sitting on a runway and not pointing straight at the ground. The conveyor belt negates the effect of the wings.

Who sent you??... it was Laminge wasn't it?... Or was it Sour bastard?..

[Casper]

Originally Posted by Black XR6

In the skateboard and elephant analogy this is a failed comparrison. The guy on the skateboard is on the conveyor, the elephant is on terra firma. The elephant is not goverened by the tredmill and will walk off. The treadmill couldnt possibly keep up with this movement. So the elephant is the thrust and is attached to the ground via its legs. The aircraft on the other hand is the skateboard guy, the skateboard and the engine. All sitting on the conveyor. Thats the difference..

And exactly how will the conveyor actually stop the engines thrust from pushing it forward? Just up and grab the underside of the plane? The conveyor has no "grip" on the plane at all. The fact that the wheels just spin around doing whatever it likes (not powered) is not "grip".
As you said, the elephant in not goverend by the tredmill... no, its not. Thats the point. The engines thrust isnt governed by the conveyor either. A planes thrust isnt based on anything on the ground. If it was a plane could not leave the ground under any circumstances without losing thrust.. which it doesnt. Thrust exists independant of what the conveyor and/or ground does. The plane will move forward, lift will be created on the wings and it will take off. The only way to stop it is to tie it down or put it in a vacuum where the engines thrust has no atmosphere to push against.

Read back through the thread, it has been explained many times.

[LTDHO]

My head hurts.
I hate you Pete. :P

Casper - what if the vehicle was a hovercraft? Would it still move forward?

I have got the staff in my office arguing now. He he

[Perana]

Damn this is still going!...

I say lock it!.. There is plenty of explanations within the last 15 pages to prove that it will take off.

[LTDHO]

Before you did the question was sent to a QANTAS technition/Systems Analyst

His reply

The statement is..."aircraft engines are there for the sole purpose to
propell the aircraft forward to produce airflow over the airfoil to create
lift which in turn, will produce flight."

So you could say, no airflow, no fly.

This is only, while all forces are parallel any move from parallel would
then produce thrust which would change the entire equation.

Use the analogy of a tethered glider or a kite, in a wind the thing will
fly but not go forward due to the tether restriction.

[THORNSPAWN]

Again with the no airflow yet no explanation as to why?
as I said earlier If the conveyor matches the forward speed of the plane
by going in reverse the plane needs to move forward in order for this to happen
no forward movement = no conveyor movement
the conveyor will not be holding the plane back (which it can't do anyway)
as even if it slows the plane the conveyor would slow down too.
Here's an interesting thought:
The surface of the conveyor moves the exact same distance backwards as the plane moves forwards. If the plane moves, at any speed, forwards 100m from it's starting
positiod the conveyor would have matched it by moving, at the same speed, 100m
in the other direction. The plane, in relation to the conveyor, would then be twice the distance from it's original starting point on the conveyor so 200m. So the plane
has moved forward as normal the only difference being the wheels have moved 200m.

[Black XR6]

The statement is..."aircraft engines are there for the sole purpose to
propell the aircraft forward to produce airflow over the airfoil to create
lift which in turn, will produce flight."

So you could say, no airflow, no fly.

This is only, while all forces are parallel any move from parallel would
then produce thrust which would change the entire equation.

Use the analogy of a tethered glider or a kite, in a wind the thing will
fly but not go forward due to the tether restriction.

Which illustrates my point perfectly.

You say the wheels do not provide power and this is exactly correct. You say nothing else restricts the plane. What about gravity. Gravity holds the plane to the ground and thus the conveyer. The plane in normal circumstances accelerates down the runway and eventually there will be enough lift created by the wings to lift the weight of the air frame off the ground and negate the effects of gravity. In the instance of the conveyor belt scenario, the plane will be held to the conveyor by gravity. Thus, with the thrust produced by the jet engines, the air frame gets moved forward. At this stage there is no lift created by the wings as the plane is not moving. The thrusty from the engines increases and the conveyor belt speeds up to counter this motion. The plane still sits in place on the conveyor relative to its surroundings.

Thus, the plane can not take off. If what you all say is true, a plane could sit on the tarmac on its wheels with breaks on. And increase thrust till it was maximum. Then the pilot could release the brakes and the aircraft would lifty off! Can not happen as no air is flowing over the wings.

Its pretty simple.

[big_pete]

Originally Posted by Black XR6

Thus, the plane can not take off. If what you all say is true, a plane could sit on the tarmac on its wheels with breaks on. And increase thrust till it was maximum. Then the pilot could release the brakes and the aircraft would lifty off! Can not happen as no air is flowing over the wings.

Its pretty simple.

ah, but wheels on the conveyer and wheels with the brakes on are not the same thing. they still spin freely with the conveyor.

:

[DivHunter]

The wheels only have to spin at twice takeoff speed and the plane will take off, woop dee doo. I think if they can handle a landing they can handle free spinning. Remember there IS airflow because the plane accelerates forward regardless of the conveyer bs. So unless there is a tail wind going faster than take-off speed it's going to fly. It will just take a little longer as it has to overcome the usual inertia plus the original reward movement the conveyer has set it on.

I still say its a harrier jet and takes off vertically melting the conveyer belt, thus making me laugh maniacaly and point at the builder of said conveyer.

[DivHunter]

Originally Posted by Black XR6

Which illustrates my point perfectly.

You say the wheels do not provide power and this is exactly correct. You say nothing else restricts the plane. What about gravity. Gravity holds the plane to the ground and thus the conveyer. The plane in normal circumstances accelerates down the runway and eventually there will be enough lift created by the wings to lift the weight of the air frame off the ground and negate the effects of gravity. In the instance of the conveyor belt scenario, the plane will be held to the conveyor by gravity. Thus, with the thrust produced by the jet engines, the air frame gets moved forward. At this stage there is no lift created by the wings as the plane is not moving. The thrusty from the engines increases and the conveyor belt speeds up to counter this motion. The plane still sits in place on the conveyor relative to its surroundings.

Thus, the plane can not take off. If what you all say is true, a plane could sit on the tarmac on its wheels with breaks on. And increase thrust till it was maximum. Then the pilot could release the brakes and the aircraft would lifty off! Can not happen as no air is flowing over the wings.

Its pretty simple.

You just need enough thrust and that IS possible _2: The air is still there and with enough thrust you would begin to move through it at such a speed as to immediately create lift.

Air is flowing over the wings anyway because the plane WILL move forward. Gravity doesn't stop the plave moving forward. Hell stand a Tomcat on its *** and it would take off it has more thrust than it weighs one of the few (only?) fighter jets that can accelerate vertically during flight.

The increasing speed of the conveyer does not increase the required thrust to move forward and or take-off.

[Casper]

Originally Posted by LTDHO

Casper - what if the vehicle was a hovercraft? Would it still move forward?

I have got the staff in my office arguing now. He he

You tell me. How much effect would a conveyor belt have on a hovercraft? I'm saying it would have no effect at all... as the hovercraft does not rely on any thrust being put through the ground other than to stay above it. Therefore (as has been seen by everyone who has ever seen TV) a hovercraft can go on basically any surface, solid or liquid, still or moving, and not be affected. It moves forward by THRUST. Stick some wings on it and it actually would fly.
The only difference between a hovercraft and this plane is that the plane has some wheels which, although are touching the ground, have no force sent through them or recieved from them by the plane. Its EXACTLY the same concept.

Based on those who say it wont fly.. if I stuck a single (freespinning)wheel in the bottom of a working hovercraft and stuck the hovercraft on the conveyor, the hovercraft would suddenly have all the thrust genereated by that bloody great big fan on the back transferred through this one single wheel and totally absorbed buy the conveyor... just because its touching it.

Ludicrous

[42.57lb]

Originally Posted by Casper

The only difference between a hovercraft and this plane is that the plane has some wheels which, although are touching the ground, have no force sent through them or recieved from them by the plane.

Sorry Casper, have to chime in mate, the wheel DOES send a force to the plane, that force is friction. Bearings reduce friction, they do not eliminate it

[Casper]

Originally Posted by 42.57lb

Sorry Casper, have to chime in mate, the wheel DOES send a force to the plane, that force is friction. Bearings reduce friction, they do not eliminate it

friction. ok, add 0.0000001% of the total thrust of the hovercraft as wheel friction. Damn, that will stop it dead now wont it. About as much difference as me sticking my foot out the door of my car at 100kph and full throttle is going to make to my cars acceleration.
Good greif.

[42.57lb]

Originally Posted by Casper

friction. ok, add 0.0000001% of the total thrust of the hovercraft as wheel friction. Damn, that will stop it dead now wont it. About as much difference as me sticking my foot out the door of my car at 100kph and full throttle is going to make to my cars acceleration.
Good greif.

Have you ever been on a plane? Notice you hear the enginges rev then you feel like you sink in your seat. So, if the was no pause maybe then there would be no rolling resistance. Rolling resistance is directly proportional to speed? so increase the speed, increase the rolling.

Oh and by the way, aircraft carriers DONT have runways that move in the opposite direction to the plane they are launching and they do have launch walls behind the plane that's launching. Also, the sling shot is fixed to the DECK that doesn't move, so you better get onto the NAVY, the airforce doesn't have any.

[Casper]

Originally Posted by 42.57lb

Have you ever been on a plane? Notice you hear the enginges rev then you feel like you sink in your seat. So, if the was no pause maybe then there would be no rolling resistance. Rolling resistance is directly proportional to speed? so increase the speed, increase the rolling.

Oh and by the way, aircraft carriers DONT have runways that move in the opposite direction to the plane they are launching and they do have launch walls behind the plane that's launching. Also, the sling shot is fixed to the DECK that doesn't move, so you better get onto the NAVY, the airforce doesn't have any.

Have I ever been in a plane? Lets see, what week? I take over 60 flights every year for work.. sometimes as much as 100 flights. Have done so for about 8 years.

I cant explain it any similar. You believe what you want, I'll believe what the vast majority.. including pilots and aerospace engineers believe.
If you honestly think 3 little wheels will have enough "friction" to overcome 40,000lb of jet thrust.. good luck to you. With that logic nones car would ever move, no train would ever run.. hell, anything with wheels would be a "friction" multiplier to the point the world would implode on itself.

I cant explain it any more simply that I have. I'll just let you believe that that sidewinder on a skateboard is going to go nowhere.. hell, we all know that the 8 wheels on a skateboard would have way more friction than any supersonic missle could ever overcome.

[42.57lb]

Originally Posted by Casper

Have I ever been in a plane? Lets see, what week? I take over 60 flights every year for work.. sometimes as much as 100 flights. Have done so for about 8 years.

I cant explain it any similar. You believe what you want, I'll believe what the vast majority.. including pilots and aerospace engineers believe.
If you honestly think 3 little wheels will have enough "friction" to overcome 40,000lb of jet thrust.. good luck to you. With that logic nones car would ever move, no train would ever run.. hell, anything with wheels would be a "friction" multiplier to the point the world would implode on itself.

I cant explain it any more simply that I have. I'll just let you believe that that sidewinder on a skateboard is going to go nowhere.. hell, we all know that the 8 wheels on a skateboard would have way more friction than any supersonic missle could ever overcome.

you know, if the run way this plane was on wasn't moving directly proportionally to the plane, I would have bowed down before your argument long ago. But you keep discounting this fact and making outlandish claims and giving examples that are similar but outside the parameters of the problem that was given. That's all mate. Don't want to insult your intelligence and for the most part I agree with you, but you keep ignoring the fact that the HYPOTHETICAL plane is on a HYPOTHETICALLY MOVING runway. You know and I know that runways don't move. Yeah, well this one does. 3 tini tiny little wheels? Yeah, they're about 6ft high, 3 feet wide and on the 747 you refer to are there about 15 of them? I don't know, I don't catch planes as often as you.

ALSO you absolutely DESTROY my arguments with, "yeah, well gee, better tell the airforce" sorry mate, that doesn't convince me, that just says your a bell end and you can't directly explain why I'm wrong.

In reality, the plane takes off, I don't disagree, you didn't need to convince me of that, but we're not talking about reality.

[Casper]

Originally Posted by 42.57lb

you know, if the run way this plane was on wasn't moving directly proportionally to the plane, I would have bowed down before your argument long ago. But you keep discounting this fact and making outlandish claims and giving examples that are similar but outside the parameters of the problem that was given. That's all mate. Don't want to insult your intelligence and for the most part I agree with you, but you keep ignoring the fact that the HYPOTHETICAL plane is on a HYPOTHETICALLY MOVING runway. You know and I know that runways don't move. Yeah, well this one does. 3 tini tiny little wheels? Yeah, they're about 6ft high, 3 feet wide and on the 747 you refer to are there about 15 of them? I don't know, I don't catch planes as often as you.

ALSO you absolutely DESTROY my arguments with, "yeah, well gee, better tell the airforce" sorry mate, that doesn't convince me, that just says your a bell end and you can't directly explain why I'm wrong.

In reality, the plane takes off, I don't disagree, you didn't need to convince me of that, but we're not talking about reality.

Sorry, Ive give you reason, logic and example. You have given me "wheel friction". The consensus is it will take off. You prove to me that it wont. You tell me how a moving runway will displace 40,000lb of thrust or more pushed into the air.
I'm tired of trying to prove it will work, 99% of people already agree with me on here. You tell me how it wont work. Tell me how the engines thrust into the air is suddenly absorbed by the conveyor that touches nothing but freespinning wheels.

[42.57lb]

if I glued a chicken to a skateboard and then put fire crackers up the chicken's erse, the I put the skatboard (with chiken attached) a tredmill, then I lit the fireworks BUT I also had a hypotheical device that instantaneoulty matched the power generated by the fireworks, but in the opposite direction, the chicken would expode on the treadmill and you would have a very messy gym.

then you would probably tell the person who own the gym that the feathers and blood everywhere had nothing to do with the chicken and the skateboard (or the fireworks) because the wheels of the skateboard are not important to the systems energy transfer.


Game over man game over, I can't convince you, you can't convince me. I'm not going to perpetuate, it. I think my education is lacing where yours is not (not being a pr1ck) so we'll just have to leave it there.

Then the RSPCA will arrest me and I'll be in jail. kool.

[Casper]

ok, so your saying that regardless of forward thrust.. the conveyor would absorb all forward movement right?