Airplane on a Conveyor Belt...

[AKIron]

Originally posted by SD67
The bottom line is, deductive reasoning has no place in the world of physics. Physics dictates that as long as the aircraft develops sufficient thrust to overcome the initial backwards force of the conveyor it WILL fly.

Assuming by "initial" you actually mean acceleration, of course it will fly. No one is arguing it won't. What is being said by some of us is that the belt may be capable of sustaining an acceleration and force transfer to the wheels equal to the thrust of the plane which keeps the plane from accelerating. At less than takeoff speed and without acceleration the plane won't fly.

[AKIron]

Originally posted by Chairboy
Yep, that must be it.

Come on Chairboy, admit there's a force you don't or didn't see here. I won't take it as an admission there might be a God.

[SD67]

Ahhh so  you're theorising upon the existence of some super conveyor.
Even so for such a super conveyor to be effective it will still need to be started even a fraction of a second before the aircraft moves. Once the aircraft gains forward momentum the conveyor cannot stop it from flying since the wheels are not the force driving it.

[AKIron]

Originally posted by SD67
Ahhh so  you're theorising upon the existence of some super conveyor.
Even so for such a super conveyor to be effective it will still need to be started even a fraction of a second before the aircraft moves. Once the aircraft gains forward momentum the conveyor cannot stop it from flying since the wheels are not the force driving it.

You're burdening me with this "super conveyor" like others have made the mistake of doing. I didn't create the scenario. I'm simply saying that under conditions given the plane won't take off if the belt can perform as the scenario dictates.

[SD67]

Sorry Iron, I didn't mean You're in the subjective sense.
I can see where the theory comes from, but in order for it to hold true the belt will still have to get the head start otherwise it will be fighting a losing battle. If the belt starts at the moment the aircraft generates forward momentum it cannot prevent the aircraft from flying. The only way the belt can prevent the aircraft from flying is if it gets the upper hand by starting first and forcing the aircraft to catch up.

[AKIron]

No offense taken SD67, I was not irritated, just making a point.

It's true that the belt lags the plane since it is afterall only responding. I think you're assuming that the belt's max power is limited to that of the plane. That was not a specified parameter. For the belt to keep the plane from accelerating it must have much more power available to it than does the plane.

[AKIron]

Understanding all aspects of this question as presented by rabbidrabbit reminds me of a riddle. To understand the solution to this riddle you have to look at it a particular way. Here's the riddle.

3 men in jail, one is blind, the other two can see

Warden has five hats, 3 are white, 2 are red

Warden tells men in jail to close their eyes and picks at random from the 5 hats and places one on each of the men's heads

Warden puts the remaining 2 hats out of sight

Warden tells men to open their eyes. Each can see the otehr's hat but cannot see their own. Of course the blind man sees nothing

Warden tells the men whoever knows what color hat is on their own head goes free

The men look at each other and think this over

Finally, 1st man says I don't know

2nd man heard the first man and also says, I don't know

3rd man who is blind, says I know

How did he know?

[SaburoS]

Originally posted by AKIron
Understanding all aspects of this question as presented by rabbidrabbit reminds me of a riddle. To understand the solution to this riddle you have to look at it a particular way. Here's the riddle.

3 men in jail, one is blind, the other two can see

Warden has five hats, 3 are white, 2 are red

Warden tells men in jail to close their eyes and picks at random from the 5 hats and places one on each of the men's heads

Warden puts the remaining 2 hats out of sight

Warden tells men to open their eyes. Each can see the otehr's hat but cannot see their own. Of course the blind man sees nothing

Warden tells the men whoever knows what color hat is on their own head goes free

The men look at each other and think this over

Finally, 1st man says I don't know

2nd man heard the first man and also says, I don't know

3rd man who is blind, says I know

How did he know?

Hmmm good one.
The blind man is wearing a white hat. If the blind man were wearing one of the two red ones, then one of the men with sight would know by virtue of what the other man with sight saw.
The moment any of the men with sight saw two red hats then by default he would be wearing the white one.
The blind man is getting the feedback from two of the men, but the men with sight are only getting one feedback as the blind man can't see the other two.
I think that's the answer. I'm tired.

[Kermit de frog]

Blind guy wears a white hat.

edit:
Explanation:

If anyone sees 2 Red hats, you'd know you were the one with the White hat.  If you saw 2 White hats or 1 white and 1 Red, then you could be wearing either a Red or White hat yourself and you would not know which one you were wearing.

The first guy doesn't know, because he doesn't see 2 red hats.  

2nd guy now knows both him and the 3rd guy are wearing white hats or 1 of each color, but not both wearing Red.  If the 2nd guy sees a Red hat on the 3rd guy, the 2nd guy would then know he was wearing White.
If the 2nd guy sees White on the 3rd guy, the 2nd guy could be wearing Red or White, therefore not knowing the answer.

3rd guy knows the 2nd guy must have seen him wearing a White hat, otherwise the 2nd guy would have known his (2nd guy) own color.

[eskimo2]

Originally posted by SD67

Sorry Iron, I didn't mean You're in the subjective sense.
I can see where the theory comes from, but in order for it to hold true the belt will still have to get the head start otherwise it will be fighting a losing battle. If the belt starts at the moment the aircraft generates forward momentum it cannot prevent the aircraft from flying. The only way the belt can prevent the aircraft from flying is if it gets the upper hand by starting first and forcing the aircraft to catch up.

SD67,

Please answer this question (note that "wheel" has been removed).

A plane is standing on a runway that can move like a giant conveyor belt. The plane applies full forward power and attempts to take off. This conveyor has a control system that tracks the plane's speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

What happens?

[stephen]

tires have nothing to do with the thrust devloped by the engine, the plane will move normaly across the face of the earth, and will lift off when the reletav air speed of the plane's wings reach  take off speed as in a normal takeoff.

Look at it this way if you have to, the tires are rotating but no matter how fast they go, that has nothing to do with the reletave speed of the airplane across the face of the earth,...only the speed at which they turn...of ourse they might be doing one hell of a click by the time the plane reaches take off speed, but the plane will take off none the less.

If as in a car, the plane was drivin by its wheels it wouldnt move, but since airplanes arent given thrust by thier tires, the answer should be inssanly obviouse.

[eskimo2]

Originally posted by stephen
tires have nothing to do with the thrust devloped by the engine, the plane will move normaly across the face of the earth, and will lift off when the reletav air speed of the plane's wings reach  take off speed as in a normal takeoff.

Look at it this way if you have to, the tires are rotating but no matter how fast they go, that has nothing to do with the reletave speed of the airplane across the face of the earth,...only the speed at which they turn...of ourse they might be doing one hell of a click by the time the plane reaches take off speed, but the plane will take off none the less.

If as in a car, the plane was drivin by its wheels it wouldnt move, but since airplanes arent given thrust by thier tires, the answer should be inssanly obviouse.

You really need to watch these:


http://hallbuzz.com/movies/wheel_on_sander_250th.AVI


http://hallbuzz.com/movies/paper_treadmill.AVI

From what you are saying, the wheel should remain stationary as the sander accelerates.  At a constant speed, the speed of the wheels does not consume/absorb energy.  Acceleration is a different matter.

[eskimo2]

BTW, here is the original AH BBS thread.

[WWhiskey]

yea and that question was flawed! just a little ways down the page you find the link to the real question from dec 2005! the person that started that thread did not state the question correctly, hence the correction! if anyone would have paid attention then we might not be having all this fun now!!
never the less V-22 osprey still flies on either test!:aok
im still waiting for you to tell me it wont and why tho

[moot]

How do a few landing gear wheels generate enough drag to stop a few jet engines from accelerating a plane to minimum takeoff speed?