A plane is standing on a movable runway(something like a conveyor) As the plane moves, the conveyor moves but in the opposite direction. The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

The question is, will the plane take off or not

so the plane is not gaining any ground speed...

how would it get any air intake into the engines? it's just spinning wheels.

my answer is no

What type of plane is it?

Not unless you're expecting 150 mph headwinds.

Oh c'mon guys, it's so simple, maybe you need a refresher course.

no

Its a jet. big ole jet airliner.
Jet engines are ON

no

lift is caused by air being forced under the wing. this would not happen because the plane isnt moving

Ginormous headwinds will be needed

Some planes can do a vertical takeoff!

But no airliners

The answer is:

Col. Mustard in the library with the revolver

the answer is 3.

you are all wrong.
the plane will take off. thats it for me.
good night

The answer is "those of you who try to show off your knowledge of physics can lick my scrotum..."

hth

The plane WILL take off.
The movement of the plane is caused by the intake of air through the turbines creating exhaust, NOT through the transfer of friction to the wheels.

Therefore, the plane will be moving just as if it weren't on the conveyor belt. The wheels will be in perpetual acceleration to keep up with the ground "matching" its velocity, though the force driving the movement of the airplane is completely independent from the relative motion of the ground.

right, its kinda the same thing as to why aircraft carriers move into the wind before launching planes.

yes.....it doesnt matter if the plane moves or not....once the speed is achieved...the plane will take off due to the difference in the wind speeds over and below the wings that would create an upthrust.

Oh no...

Go to www.flightinfo.com (pilot website) and search for a thread with the same question...it was something like 50 pages of grown men arguing like kids about whether the plane would take off or not.

I guess it's only right to answer the question. I don't think it will take off. Now I also know that I could be totally wrong, so if someone could exaplain to me how a plane can take off with no airflow over the wings, i'll glady change my position!

It's a paradox. The plane's wheels continually accelerate to keep up with the plane being pushed forward plus the conveyer accelerating trying to match... tada... the wheels. You end up with an X = X + Y situation, with X, Y > 0.

The positive feedback loop exists, and the wheels would be destroyed long before the plane developed any forward airspeed.

this guy reads OT

of course it will take off.....the wheels free roll and do not affect the plane moving forward at all...idiots, all of you

quote:

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The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

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There's some substantial vagueness here. How is the 'speed' of the plane measured by the tracking system?

If the tracking system has control logic that dictates "if plane is moving forward relative to the air, accelerate belt until plane is not moving forward relative to the air", then the destruction scenario I mentioned above takes place.


The physicists want to think of this as roughly the equivalent of a free moving belt riding on some sort of frictionless ball bearings (or a sheet of frictionless ice), illustrating this point in propulsion differences: If a car was on such a system, the car would remain stationary (the belt moving backwards), whereas a plane would not (the belt remaining stationary).

However, that is not the system as posed by the question. The system, as stated, would actively accelerate the belt to an infinite speed in short order.




[This message has been edited by Keegan99 (edited 11/29/2006 1:42a).]

stop putting so much thought into it....it takes off, the conveyor does not hinder the planes ability to accelerate at all

Again, how is the 'speed' of the plane measured by the tracking system? That is, how is the speed of the conveyer determined?

If the control logic I indicated above governs the system, then the plane's wheels and/or the conveyer will be destroyed before the plane reaches any significant forward speed.

The question is poorly worded and requires better definitions.

i hope you are joking around keegan........

No, I'm not.

Specify how the control system measures the 'speed of the plane', thus controlling the speed of the belt.

The conveyer belt is not a sheet of ice. It's a system with mechanical limits, as are the plane wheels.

? when the plane reaches its take-off speed (which it will just as if it were on a regular runway) it will takeoff. Your thoughts that you laid out concerning the speed of the conveyor are pointless......who cares how fast the conveyor goes, it won't concern the speed of the airplane.

Theoretically, you are correct.

However, when the question says the conveyer matches the 'speed of the plane', how is that determined?

quote:

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who cares how fast the conveyor goes, it won't concern the speed of the airplane.

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No, but it concerns the speed of the wheels!

If the conveyer is going 700MPH, the plane wheels would fail long before the plane could take off. A 100MPH airspeed with a 700MPH conveyer means the wheels are turning at 800MPH. Plane wheels are tough, but not that tough. They would be destroyed, and so would the plane!


The question as stated is ambiguous and insufficient, though a reasonable attempt to cleverly illustrate differences in propulsion. Definitions of concepts and implementation details (ie how, exactly, is the speed of the belt determined?) are required to determine what would really happen if such a system were constructed.


[This message has been edited by Keegan99 (edited 11/29/2006 2:12a).]

should have checked your profile software engineer.......over thinking problems that have a simple explanation and fretting details that don't really matter

I understand your points, and see that you have gotten the point of question so bravo for the detailed arguments

Saw this on another board. The majority of people said no, but the people who said yes seemed to be pretty dam intent on the fact that the airplane could take off.

it will take off.....no question about it, end thread

quote:

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The movement of the plane is caused by the intake of air through the turbines creating exhaust, NOT through the transfer of friction to the wheels.

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The MOVEMENT of the plane is controlled by that.

The FLIGHT of the plane is controlled by the air moving over the wings. Since the plane is remaining stationary in relation to the air, no, it won't take off.

They conveyor belt is moot.