Newtons law of motion.

an object in motion will stay in motion and an object at rest will stay at rest unless acted on by an unbalanced force.

OK, in a nutshell. The speed of the plane is AT ALL TIMES relevant to the opposite speed of the conveyorbelt, because it has some sort of compensator to maintain that equilibrium.It is never relevant to the surrounding air, because it is stationary, just as the plane is IN RELATION TO THE AIR, NOT THE CONVEYORBELT.Sorry to shout, but I summed it up quite simply before. The engines only provide propulsion in an aeroplane.The wings provide the lift.Look at it this way. Forget the conveyor belt!! Imagine a plane is facing north along a runway.It requires forward motion of say 120 mph to give the wings ,cutting through relatively motionless air, enough lift to let the plane leave the ground.A tailwind of 125 mph is blowing. The plane reaches what would be a normal take-off speed of 120 mph...but in relation to the TAILWIND of 125mph, the wings are getting no lift, because the wind is going faster than the wings!! The plane could try for 100.000 miles to take off, but would never manage it. Why not? the engines are pushing it forward in relation to the ground, at liftoff speed.But, the wind is going at the same speed as the wings!!. So, if the pilot could open up the engines to 250 mph, it would take off...providing the wind stayed at 125mph. But, in this case, the wind would increase its speed in line with the plane, and the plane would still be experiencing no lift from the wings.
Nick

Here's another question sort of along the same lines:

If lift-off of a particular aircraft occurs at say 150MPH (I'm just guessing), would that same aircraft be able to lift off while standing still if it was pointed straight into a 150MPH (or higher) hurricane?

I suspect this has happened accidently to some degree, probably with a bad ending!

quote Originally posted by Patrick: Here's another question sort of along the same lines: If lift-off of a particular aircraft occurs at say 150MPH (I'm just guessing), would that same aircraft be able to lift off while standing still if it was pointed straight into a 150MPH (or higher) hurricane? I suspect this has happened accidently to some degree, probably with a bad ending!

Yes! That is why they tie aircrafts down. If they didn't, in a strong wing, it would fly off the ground.

I'm not, I've said repeatedly that it can be prop, jet, or even rocket. Unless you're inventing a new type of aircraft that uses the wheels as the primary motive force, the conveyor belt will have no effect on how the aircraft moves.

John Stricker

quote Originally posted by Patrick: Nick, isn't it weird how certain aspects of the proposed scenario are simply ignored (or missed) by a lot of people. The scenario itself may be flawed, but working with what we're given, this plane will not take off. By the way, why are so many of you convinced that this plane has a prop?

quote Originally posted by naskie18: ....its boring if you all just agree with me

You happy now .

How the hell does this stupid question get 3 pages? Supose the craft was an alien UFO? And you were in the Bermuda Triangle and had the ability to take advantage of a 4th dimension? NOW it's a challenging question!

The original supposition:

quote

A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction).
The question is:

Will the plane take off or not?

To be frank, it's a stupid question without enough data to answer. it says "This conveyer has a control system that tracks the plane speed". Relative to what? Airspeed? Groundspeed? Wheelspeed? What?

Using a practical example based on virtually all aircraft that take off on a runway today, the wheels do not provide the motive force so, try as the conveyor might, it would be unable to keep the aircraft from accelerating.

Now if we go with some imaginary airplane with a new set of conditions, that will make the wheelspeed exactly match the calculated groundspeed, then no, the aircraft can't take off because it would have NO relative motion.

In the real world, the conveyor belt will have no effect on the prime motive force of the aircraft, be that prop, jet, or rocket. If you want to make up an imaginary aircraft, fine, state so in the conditions. Then we'd have a question about an imaginary aircraft on an imaginary runway, neither of which exist.

John Stricker

quote Originally posted by fierofetish: OK, in a nutshell. The speed of the plane is AT ALL TIMES relevant to the opposite speed of the conveyorbelt, because it has some sort of compensator to maintain that equilibrium.It is never relevant to the surrounding air, because it is stationary, just as the plane is IN RELATION TO THE AIR, NOT THE CONVEYORBELT.Sorry to shout, but I summed it up quite simply before. The engines only provide propulsion in an aeroplane.The wings provide the lift.Look at it this way. Forget the conveyor belt!! Imagine a plane is facing north along a runway.It requires forward motion of say 120 mph to give the wings ,cutting through relatively motionless air, enough lift to let the plane leave the ground.A tailwind of 125 mph is blowing. The plane reaches what would be a normal take-off speed of 120 mph...but in relation to the TAILWIND of 125mph, the wings are getting no lift, because the wind is going faster than the wings!! The plane could try for 100.000 miles to take off, but would never manage it. Why not? the engines are pushing it forward in relation to the ground, at liftoff speed.But, the wind is going at the same speed as the wings!!. So, if the pilot could open up the engines to 250 mph, it would take off...providing the wind stayed at 125mph. But, in this case, the wind would increase its speed in line with the plane, and the plane would still be experiencing no lift from the wings. Nick

Only you fixed wing jocks would have to even consider these things.
That sucker's gonna fly like there's no tomorrow. The wheel bearings may get hot, melt, & the races fuse together, but the plane will take off, dragging the siezed wheels, with their now flame engulfed tires along the speeding conveyor.

The real question.
On a plain out in the middle of an Iowa cornfield sits an open elevator with a 300' high travel limit, topped with a flat platform of expanded metal (mesh). The elevator is "down", at it lowest point. A helicopter sits on top of the platform. The helo's blades begin to rotate generating lift. As lift is increased, a matching rise in the elevator is maintained. Will the helo take off before the elevator reaches it's 300' high travel limit? 0 altitude is considered to be the top surface of the iron mesh platform

(Hint)define 'lift'.

[This message has been edited by maryjane (edited 12-02-2005).]

If the scenario depicted were physically possible, the plane woould be standing still. the wheels would be rotating at the same speed as the conveyorbelt, on which it was standing.BUT, the plane ITSELF would have no forward momentum. Therefore the wings would not be generating any lift, because the air is stationary, in relation to the ground, as would the wings be, in relation to the ground and surrounding air.No forward momentum through the stationary air, no lift. I will bet all my worldly possessions that this is correct!!! Last time: Aeroplane engines provide forward propulsion, through the stationary air, which acts on the aerofoil surfaces of the wings. If the engine propulsion is constantly equivalent to the opposite speed generated by the conveyorbelt, that said propulsion will maintain the plane in a stationary state as relative to the surrounding air, although the plane will be moving 'forward' at 120 mph in relation to the conveyorbelt, but not the surrounding air.The wings provide the secondary, but equally relevant force which enables a plane to fly..lift.By moving through the stationary air at sufficient speed to create an upward 'suction' on the wing surface.
Edit to say: John, I type slower than you!! I am only arguing the scenario as it is stated. It is an imaginary situation, and I am only arguing within the facts supplied.The scenario is, that the takeoff strip is capable of moving backwards, at the same speed as the plane moves forward.Now, if that is possible in reality is rediculous, but that is the formula supplied.Therefore, there would be no forward motion, and so no lift. I am not trying to make it feasible in real life, only within the confines of the problem or challenge as written!! In real life it couldn't happen.But in the scenario propounded, it would not fly

[This message has been edited by fierofetish (edited 12-02-2005).]

Let us look at a J3 piper Cub.
It will lift off the ground a 35 MPH.
A point on the conveyor belt would be running at 35 in the opposite direction with a relative speed of 70 to the J3s tires as the J3 lifts off the ground.

An A/A fuel dragster would go no where, it,s AXLE DRIVEN.
Ground contact means nothing to an airplane.

<<<<< will I reach 3700 before you give in??? I doubt it!!! !!!

You are so wrong!! Contact with the ground gives the plane forward impetus, which in turn forces the wings through the air , which in turn allows them to create lift!!
If you were able to suspend a jumbo jet 100 feet in mid air, and keep it stationary, with the engines on full blast, what would happen to the plane when you released it from its mooring? It would start to move forward, under the engines' propulsion, but it would fall to the ground, because almost negative movement of air over the wings is not creating enough lift to keep it up, even though the engines were giving it forward motion!! If, however, it was suspended at say 20.000 feet from the ground, the engines would give it enough speed to create lift on the wings, allowing the plane to reach optimum speed for the wings to generate sufficient lift before it hit the ground. That is why jet fighters have to be launched by catapult from the deck of a Carrier. To give it enough forward speed for the wings to be able to lift it into the air.If the contact with the ground is irrelevant, as you are suggesting, why do we need runways 2 miles long for planes to be able to take off? A plane can never leave the ground until it reaches liftoff speed.Therefore it need contact with the ground to take the load until the wings have sufficient lift to take over.
Nick

quote Originally posted by Wolfhound: Let us look at a J3 piper Cub. It will lift off the ground a 35 MPH. A point on the conveyor belt would be running at 35 in the opposite direction with a relative speed of 70 to the J3s tires as the J3 lifts off the ground. An A/A fuel dragster would go no where, it,s AXLE DRIVEN. Ground contact means nothing to an airplane.

[This message has been edited by fierofetish (edited 12-02-2005).]

quote Originally posted by fierofetish: You are so wrong!! Contact with the ground gives the plane forward impetus, which in turn forces the wings through the air , which in turn allows them to create lift!!

WRONG!!! WRONG!!! WRONG!!!

Contact with the ground does jack **** for a plane. The ONLY thing that provides forward motion for a plane is the engine pushing air backwards.

quote If you were able to suspend a jumbo jet 100 feet in mid air, and keep it stationary, with the engines on full blast, what would happen to the plane when you released it from its mooring? It would start to move forward, under the engines' propulsion, but it would fall to the ground, because almost negative movement of air over the wings is not creating enough lift to keep it up, even though the engines were giving it forward motion!!

This is correct. But it is not the original item.

quote If, however, it was suspended at say 20.000 feet from the ground, the engines would give it enough speed to create lift on the wings, allowing the plane to reach optimum speed for the wings to generate sufficient lift before it hit the ground.

True. But again it is not the original item.

quote That is why jet fighters have to be launched by catapult from the deck of a Carrier. To give it enough forward speed for the wings to be able to lift it into the air.

True. The aircraft engines are not strong enough to accelerate the aircraft to the airspeed required in the short distance of the carrier deck.

quote If the contact with the ground is irrelevant, as you are suggesting, why do we need runways 2 miles long for planes to be able to take off?

Wrong. The contact with the ground is not irrelevant. The groundspeed is irrelivant. The reason we need runways 2 miles long is because it takes a long time for airliners to accelerate up to the airspeed required to take off.

quote A plane can never leave the ground until it reaches liftoff speed.Therefore it need contact with the ground to take the load until the wings have sufficient lift to take over.

True. And the aircraft is sitting on the conveyor belt until it gets enough airspeed to lift off.

[This message has been edited by Steve Normington (edited 12-02-2005).]

quote Originally posted by fierofetish: OK, in a nutshell. The speed of the plane is AT ALL TIMES relevant to the opposite speed of the conveyorbelt, because it has some sort of compensator to maintain that equilibrium.It is never relevant to the surrounding air, because it is stationary, just as the plane is IN RELATION TO THE AIR, NOT THE CONVEYORBELT.Sorry to shout, but I summed it up quite simply before. The engines only provide propulsion in an aeroplane.The wings provide the lift.Look at it this way. Forget the conveyor belt!! Imagine a plane is facing north along a runway.It requires forward motion of say 120 mph to give the wings ,cutting through relatively motionless air, enough lift to let the plane leave the ground.A tailwind of 125 mph is blowing. The plane reaches what would be a normal take-off speed of 120 mph...but in relation to the TAILWIND of 125mph, the wings are getting no lift, because the wind is going faster than the wings!! The plane could try for 100.000 miles to take off, but would never manage it. Why not? the engines are pushing it forward in relation to the ground, at liftoff speed.But, the wind is going at the same speed as the wings!!. So, if the pilot could open up the engines to 250 mph, it would take off...providing the wind stayed at 125mph. But, in this case, the wind would increase its speed in line with the plane, and the plane would still be experiencing no lift from the wings. Nick

Nope.

All of your scenarios are assuming a car with wings. When the car drives up to a certain speed, it will take off. In that case, yes, the moving conveyor belt would cancel out the forward movement of the car, and relative movement would be zero. That's because the friction between the car's wheels and the conveyor surface provide the motion.

On an aircraft, the friction with the runway surface is not a factor in takeoff. Once you apply thrust, the plane *will* move forward. I don't care how fast you turn the imaginary conveyor belt. Even if this magical speed device always matches the speed of the treadmill to the forward speed of the plane, the two speeds do not cancel each other out. The movement of the airplane is irrelevant to the speed of the treadmill.

Take the wheels off the plane. Put skis on it. Place it on a sheet of ice. Now apply thrust to move the plane forward at 5 mph. The plane is now moving at 5 mph through the air. Now, somehow speed the ice up under the plane to 5 mph in the other direction. The plane is *still* moving through the air with a forward velocity of 5 mph. Speed the ice up to 20 mph. The plane is *still* moving through the air at a forward velocity of 5 mph. The thrust of the engine is pushing the plane through the air. The thrust force is against the air behind the plane, not the ground. The plane can apply more thrust and accelerate at will to takeoff speed. The speed at which the ground surface is passing underneath it is totally irrelevant.

You are assuming that if the speed of the conveyor is always equal to the speed of the airplane, they will cancel each other out. I am saying that they can't cancel each other out as long as the plane has enough power to take off normally. The plane does not act against the runway. The two forces are not in opposition. They are separate vectors.

Edit: It says nowhere in the original problem that the plane remains stationary. You are making that supposition based on flawed physics.

[This message has been edited by Gary W (edited 12-02-2005).]

Once again, reread the question, the 'conveyer belt' is just a red harring I believe. What he meant was with zero ground speed.

fierofetish, maybe this will help.

I'm in a Cessna flying 75 mph North. I fly over a long train heading 75 mph South. I fly to where my wheels are within 1 inch of the top of the train (very smooth train and tracks). I'm still flying because I'm going 75 mph in the air.

My wheels briefly touch the train that is going 75 mph south while I go 75 mph north.

Do I suddenly crash onto the train because the train canceled out my airspeed north?

quote Originally posted by JohnnyK: Once again, reread the question, the 'conveyer belt' is just a red harring I believe. What he meant was with zero ground speed.

Ground speed means nothing to an aircraft. Airspeed is the only thing that matters to lift.

[This message has been edited by Steve Normington (edited 12-02-2005).]

quote Originally posted by Steve Normington: fierofetish, maybe this will help. I'm in a Cessna flying 75 mph North. I fly over a long train heading 75 mph South. I fly to where my wheels are within 1 inch of the top of the train (very smooth train and tracks). I'm still flying because I'm going 75 mph in the air. My wheels briefly touch the train that is going 75 mph south while I go 75 mph north. Do I suddenly crash onto the train because the train canceled out my airspeed north? Ground speed means nothing to an aircraft. Airspeed is the only thing that matters to lift.

Yes, thank you for that. THe question doesn't specify, therefore 0.

I wish I could make my letters big too!!!

The contact with the ground is the biggest factor in the initial takeoff, because it supports the weight of the plane, until the wings provide enough lift, through forward motion through the air, to support the weight of the plane.
The movement over the ground, provided by forward propulsion by the engines, through the stationary air, will provide that lift when the plane reaches the required speed. Let';s just say 120mph for an example.The speed of the plane is not relevant to the ground it passes over, but the air it is passing through.Assuming there is no windspeed at all, the air is then travelling at 0 mph in relation to the ground.Therefore the plane will need to reach 121 mph before the wings will generate enough lift through the air for the plane to leave the stationary ground.But, if the imaginary conveyorbelt, upon which the plane is standing, is running backwards at 125 mph that is -0125mph in relation to the static wind.But the plane is running along the conveyorbelt at 125mph, but still only at 0 mph in relation to the air.That means the wings are not travelling through the motionless air, and are therefore not creating lift.

What the heck. I'll play. The way I see it this has to be hypothetical to be worth thinking about. We must then assume unlimited speed of the conveyor as well as unlimited power from the drive force of the plane. The plane is not moving relative to the area it is in so conventional lift from the wings is probably not effective. So, when does the plane then become a rocket. At that point forward thrust of the plane will cause the plane to rise off the conveyor and continue to move the plane forward as if it were a cruise missle being launched horizontally. As with the Harrier, if the thrust is concentrated in the correct position, the plane will continue to move forward until lift can be sustained and controlled by the wings.
If the example uses conventional and existing technology then I don't think it can achieve enough thrust to overcome gravity. The wheel and conveyor bearings will melt and the whole thing would blow up because a seagull flew into the intake. But then again the question was "will it fly?" Is a rocke t a plane?

Think of it this way:

The airplane is an airboat.
The runway is water.

No matter how fast the water is flowing, the airboat will always be able to go upstream. The water doesn't matter. The airboat is pushing air. If it had wings, it would accelerate to takeoff speed (relative to the air) and it would fly.

Now, a normal boat with a prop or a jet drive IN THE WATER would have a problem. The speed of the water over the propeller or through the jet drive would have to be overcome before forward motion were possible. Given an infinite water speed, you could prevent the boat from moving.

After rethinking this a bit I have concluded that the plane will fly. The airplane is generating thrust against the air, unless it is tethered it will begin to move foward, pushing against the air to move itself. The conveyor is irrelevant. As soon as it reaches enough speed to create lift it will fly. I have seen small planes lift off the ground in high winds. Their relative ground speed was zero but the wind going over the wings was fast enough to create lift.

I have never seen a rocket lauched horizontal to the ground!! If it was, it would continue to fly at t ground level, until it flew into something that was higher that it was flying!! (Unless it had wings, or aerofoils, that could be controlled, to give it lift..then we are back to the same point, aren't we?? )
Nick

quote Originally posted by Mytime: What the heck. I'll play. The way I see it this has to be hypothetical to be worth thinking about. We must then assume unlimited speed of the conveyor as well as unlimited power from the drive force of the plane. The plane is not moving relative to the area it is in so conventional lift from the wings is probably not effective. So, when does the plane then become a rocket. At that point forward thrust of the plane will cause the plane to rise off the conveyor and continue to move the plane forward as if it were a cruise missle being launched horizontally. As with the Harrier, if the thrust is concentrated in the correct position, the plane will continue to move forward until lift can be sustained and controlled by the wings. If the example uses conventional and existing technology then I don't think it can achieve enough thrust to overcome gravity. The wheel and conveyor bearings will melt and the whole thing would blow up because a seagull flew into the intake. But then again the question was "will it fly?" Is a rocke t a plane?

Controlled thrust.

quote Originally posted by fierofetish: I think you must all re-read the description !! It will not take off!! The conveyor belt is controlled to provide the same rearward motion of the conveyorbelt, as the forward motion of the plane. Nick

Here is the flaw in your reasoning. The original question stated that the conveyor SPEED is controlled relative to the SPEED of the plane. It says nowhere that the MOTION of the plane is cancelled out by the MOTION of the runway. The SPEED of the conveyor has nothing to do with the MOTION of the plane. The MOTION of the plane is created by thrust of the engine against the AIR not against the runway. Now if the speed of the AIR were controlled relative to the speed of the PLANE, we would have a problem.

quote Originally posted by Gary W: Here is the flaw in your reasoning. The original question stated that the conveyor SPEED is controlled relative to the SPEED of the plane. It says nowhere that the MOTION of the plane is cancelled out by the MOTION of the runway. The SPEED of the conveyor has nothing to do with the MOTION of the plane. The MOTION of the plane is created by thrust of the engine against the AIR not against the runway. Now if the speed of the AIR were controlled relative to the speed of the PLANE, we would have a problem.

It's implied, it's a poorly worded question.

I am the first to say (along with all the others!!), that the scenario is purely theoretical, and I should imagine impossible in real life.That out of the way:
An aeroplane requires 2 forces to fly, in still air. Propulsion, and lift. I know we all agree to that!!
To use the example of planes lifting off in high winds is not relevant. Why? Because it would only be using one of the required forces. In this case lift, provided by high headwinds acting on the aerofoils of the wings. It would lift into the air. I don't dispute that. It might hover, if the wind was constant, and prevailing.But, it would not move forward.It would crash, as they all do in these cases.
I accept Roger's point about airspeed being totally unrelated to groundspeed, in order to fly.But, airspeed has to be attained by moving along the ground, which supports the weight of the aircraft until the lift, caused by airspeed, enables the wings to take over from the wheels in supporting the weight of the aircraft.
I have taken the airspeed ( speed of the air in relation to the ground, and hence the plane standing on it), as being nil in this scenario. There is no mention of hurricanes or tornadoes!! so a normal mean windspeed encountered in normal conditions would be fairly irrelevant, I would have thought.
I have accepted the given theory that the conveyorbelt will be able to match the potential ground speed up to infinity.Therefore, the plane would have no forward motion, and therefore no lift created by the wings, because the air is static in relation to the lack of forward motion of the wings
All these things taken into account, the plane could not fly.
Nick

quote Originally posted by JohnnyK: It's implied, it's a poorly worded question.

It's not implied at all. In fact, it says that the plane moves forward and the runway moves backward. The two movements are not related - that's the whole point of the question. If the two motions are not related, they cannot cancel each other out. It never says the plane stands still. I'm saying that no matter how fast the runway moves backward, the plane will STILL move forward, because the plane does not interact with the runway for its forward velocity. It interacts with the air. It's simple physics.

quote Originally posted by Gary W: It's simple physics.

Yes, I know, and I'm quite good at that and aero. However, I'm interpreting this question like he meant the plane had 0 ground speed with the runway rocketing beneath him. As I've stated, the question is worded poorly, and can be interpreted both ways.

quote Originally posted by fierofetish: Look at it this way..please!! I agree with what you are saying about thrust.No dispute. But, the thrust from the engines against the air is only compensating for the fact that the conveyorbelt would be carrying the plane backwards, and would fall off the end (if it had an end!!), unless the engines generate enough force against the static air to maintain the craft in its position, rolling on its wheels,in relation to the earth (ground) around the belt...and therefore the static air too If the engines were not on thrust, and the belt was moving backwards, so too would the plane.Therefore, the ability to adjust the speed of the belt to exactly equal the forward motion generated by the engine thrust, would keep the plane static, in reation to the air around it, and no lift! Nick

But you're thinking that the friction of the plane against the runway will increase with speed, requiring all of the plane's thrust to be used against the motion of the runway. It will not. The runway will NOT carry the plane backwards - it will simply move under the wheels. The runway would only carry the plane backwards if the plane had its brakes on. Once initial friction is overcome and the wheels are rolling, the speed of the runway becomes irrelevant. The plane is now moving. The tires are not pushing against the runway - the engines are pushing against the air. The air is still static, so the plane moves forward.

Edit to fix quote tag

[This message has been edited by Gary W (edited 12-02-2005).]

A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. ******This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction).****
The question is:

Will the plane take off or not?

That could not be interpreted any other way, surely?
The only other variable which could affect things in this scenario, and isn't mentioned, is actual speed of the air, or in which direction, in relation to the aeroplane's wings I have taken that to mean it would be near enough nil.
Nick

Edit for Gary:

I make no allowance at all for friction..it doesn't come into it.If a plane was static, on its wheels, on a static belt, and the belt started to move, the wheels would not turn, unless the belt jerked from 0 mph to say 20 mph in a split second. The weight of the plane bearing down would hold the wheels, and the plane, still, assuming the belt was totally level.....IMHO!!!! I just experimented on my tabletop, with a model car, standing on a sheet of paper. If I pull the sheet of paper gently and evenly, the car stays static, and moves along the tabletop, on the paper.It didn't move, in relation to its position on the paper. If I jerked it, it would move forward on the paper, but would remain static in relation to the tabletop..until it reahed the edge of the paper, and then rolled a small amount on the table top, until the momentum of the car's mass expired. Try it!!
Nick

[This message has been edited by fierofetish (edited 12-02-2005).]

Lets for a moment, pretend it's not a 'conveyer belt', but something that is somehow magically attached to the plane, and keeps dragging it back, which is what was intended I believe.

Read the problem stated on page one. No magic involved .

quote Originally posted by JohnnyK: Lets for a moment, pretend it's not a 'conveyer belt', but something that is somehow magically attached to the plane, and keeps dragging it back, which is what was intended I believe.

OK. That would be like saying that the plane were nailed to the ground. No amount of thrust would get it to move relative to the ground or the air. It would not move, and it would not fly. But the question was not about pretending it was NOT on a conveyor belt. This is a Physics test question we actually debated in college. It's meant to challenge the way you look at the problem, and the question is asked in a very specific way for a specific reason. As put forth in the original question, making no assumptions or interpretations of what you think somebody was asking, the plane will accelerate down the moving runway and take off.

Has Naskie18 gone to bed? Can you post the link to the other Forum? I would lve to read it!!
And now, thanks to you all for a great debate..but it is 3:31am, and I am off to bed!! Hope you post that link..it has been fascinating!!
Best wishes to All my protagonists..it has been a great debate!!!
Nick

quote Originally posted by fierofetish: Edit for Gary: I make no allowance at all for friction..it doesn't come into it.If a plane was static, on its wheels, on a static belt, and the belt started to move, the wheels would not turn, unless the belt jerked from 0 mph to say 20 mph in a split second. The weight of the plane bearing down would hold the wheels, and the plane, still, assuming the belt was totally level.....IMHO!!!! I just experimented on my tabletop, with a model car, standing on a sheet of paper. If I pull the sheet of paper gently and evenly, the car stays static, and moves along the tabletop, on the paper.It didn't move, in relation to its position on the paper. If I jerked it, it would move forward on the paper, but would remain static in relation to the tabletop..until it reahed the edge of the paper, and then rolled a small amount on the table top, until the momentum of the car's mass expired. Try it!! Nick

You just made my point. Put a rocket motor on top of the model car. Pull the sheet of paper and the car will remain static. Light the rocket and the car will shoot off the end of the paper. It doesn't matter how fast you pull the paper, because the rocket motor is pushing the car through the AIR, not on the paper.

quote Originally posted by Gary W: You just made my point. Put a rocket motor on top of the model car. Pull the sheet of paper and the car will remain static. Light the rocket and the car will shoot off the end of the paper. It doesn't matter how fast you pull the paper, because the rocket motor is pushing the car through the AIR, not on the paper.

Sorry...!!! The inference is that the belt matches EXACTLY the speed etc of the plane. If the plane accelerates at 0-500mph in 2 seconds...so too does the belt..and so it won't shoot off the end of the paper!!! The belt doesn't have an end!!! The plane stays static in relation to the air that surrounds it..so no lift!!!
Night!! Time for bed!!!
Nick