Airplane on a Conveyor Belt...

[john9001]

originial question.

"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."


<<<>>>>


it says the planes speed, if this plane can rotate and fly at 50 mph then the belt will being moving 50mph  in the opposite direction. I doubt the wheels will be turning at 100,000 rpm at that speed.

If the plane holds it's speed at 50mph there will be no more acceleration from the belt, then the plane lifts off.


a note here, it does not mean the plans speed over the belt, it means the planes ground speed.

[Donzo]

So......

If we used this magical conveyor runway when landing a plane, would the plane come to a dead stop immediately after touching down?

[WWhiskey]

v-22 still takes off!

[SD67]

Originally posted by Donzo
So......

If we used this magical conveyor runway when landing a plane, would the plane come to a dead stop immediately after touching down?

Actually this is pretty close to being true. On landing the aircraft is usually generating very little thrust, most are on what is termed a "glide approach". In this case, landing on a conveyor style runway will actually shorten the apparent landing distance significantly. The actual rolling distance will be similar, but that is absorbed by the belt.
It is only when the equation of positive thrust comes into it that the conveyor ceases to be effective in arresting the aircrafts' forward motion.

[eskimo2]

Originally posted by john9001
originial question.

"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."

 

That's an alternate question that has been simplified.

Here’s the original AH BBS question from last year:

Originally posted by rabbidrabbit
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 wheel speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

The question is:

Will the plane take off or not?

[Chairboy]

Originally posted by eskimo2
I can only conclude that you are not bright enough to comprehend the question, or too arrogant to even consider carefully reading it.

Yep, that must be it.

[WWhiskey]

Originally posted by WWhiskey
the original question  from the Neal Boortz show that started this whole thing

" If an airplane is on a large conveyor belt and is trying to take off by exerting the thrust needed to move forward at 100knots, and the conveyor belt starts moving backwards at 100 knots, will the plane be able to take off, or will it just sit stationary relative to the ground, with the backwards speed of the conveyor belt counteracting the forward thrust of the plane?"

that is all it asks, nothing more, nothing less.
 the plane will fly!
where everyone got the rest of the problems for this riddle is from other peoples answers and solutions to a problem that did not exist in the original question!

http://txfx.net/2005/12/08/airplane-on-a-conveyor-belt/
this shows the original question from december of 2005

 
Eskimo2, this is the original question from 2005, not the one by John9001
some of us are woking on the real question that was answered on Mythbusters not the changed version that came out later, but the V-22 still flies in either question!

[VERTEX]

Originally posted by eskimo2
Imagine the wheel is only rolling 2 mph on the treadmill, and its center/axle is moving down the runway at 1 mph.  The treadmill must be going only 1 mph…  In this case the treadmill is not matching the wheel’s speed.

Do you agree?

Speed is a measure of distance traveled in a certain period of time. The wheel will have a speed as it is carried forward along with the axle that is the same as the airplane as a whole.

The rotation of the wheel about the axle, and the rotation of the conveyor belt are separate from the forward speed of the airplane. The wheel and conveyor can rotate in any direction, forwards or backwards and the plane will fly since the free wheeling nature of the wheel isolates the airplane from any influence the conveyor might have.

I am repeating myself here, why cant you get this.

[SFRT - Frenchy]

Eskimo, not sure of what you want me to answer here ...

Al's plane will take off in 100ft, Bob's in less than AL's, and Chuck in less than Bob's. No rotational inertia will not mean that Chuck's plane will take off in 0ft.

The rotational inertia will just make it harder to spin the wheels, which will translate to the plane as drag. If you remove the rotational inertia of the wheels, you remove the drag induced by the wheel mass on the wheel axle.

You still have the aerodynamic drag of the wheel, plus the wheel drag induced by the contact of the tire to the ground plus all the gazzilions drag forces that apply to the plane.

So back to the "original question"

" If an airplane is on a large conveyor belt and is trying to take off by exerting the thrust needed to move forward at 100knots, and the conveyor belt starts moving backwards at 100 knots, will the plane be able to take off, or will it just sit stationary relative to the ground, with the backwards speed of the conveyor belt counteracting the forward thrust of the plane?"

Since you guys masturbate your brain with the conveyor, just remove the sucker. All the conveyor does is spin my wheels at 100knots. So suspend my plane in the air with a crane. Get an electric engine that spins my wheels at 100 knots, release me and watch me pancake myself.

Or the question is actually, I'm acceleration to 100kt and at 100kt the wheels spin backward ... will I take off?

Or the question is actually, I'm acceleration to 100kt and at 100kt I lock the wheels ... will I take off?

What needs 13 pages of debating?

[Golfer]

What if the plane is trying to take off on a belt sander?

What if we vary the grit od the sandpaper?

[eskimo2]

Originally posted by SFRT - Frenchy


 All the conveyor does is spin my wheels at 100knots.

Why 100 knots?  Why did you choose that speed?

[eskimo2]

Originally posted by VERTEX
Speed is a measure of distance traveled in a certain period of time. The wheel will have a speed as it is carried forward along with the axle that is the same as the airplane as a whole.

The rotation of the wheel about the axle, and the rotation of the conveyor belt are separate from the forward speed of the airplane. The wheel and conveyor can rotate in any direction, forwards or backwards and the plane will fly since the free wheeling nature of the wheel isolates the airplane from any influence the conveyor might have.

I am repeating myself here, why cant you get this.

Suppose the wheel is only rolling 2 mph on the treadmill, but its center/axle is not moving down the runway.  The treadmill also must be going 2 mph…  In this case the treadmill is matching the wheel’s speed.

Now imagine the wheel is only rolling 2 mph on the treadmill, and its center/axle is moving down the runway at 1 mph.  The treadmill must be going only 1 mph…  In this case the treadmill is not matching the wheel’s speed.

Now imagine the wheel is rolling 1,002 mph on the treadmill, and its center/axle is moving down the runway at 1 mph.  The treadmill must be going  1,001 mph…  In this case also, the treadmill is not matching the wheel’s speed.

[eskimo2]

Originally posted by WWhiskey
Eskimo2, this is the original question from 2005, not the one by John9001
some of us are woking on the real question that was answered on Mythbusters not the changed version that came out later, but the V-22 still flies in either question!

Here is the original AH BBS question from last year:

Originally posted by rabbidrabbit
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 wheel speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.

The question is:

Will the plane take off or not?

I have no problem with the plane taking off if the conveyor matches the plane’s speed.  This question is different; the wheel speed factor changes everything!

[SD67]

Some of the reasoning I see in this thread reminds me of the old question  about the race between Achilles and a tortoise.
Aristotle reasoned that If the tortoise had a head start Achilles could never defeat him in a race because by the time Achilles reached the point where the tortoise was, the tortoise would have move on, and so on and so forth. This is much the same sort of reasoning I see happening here. 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.

[john9001]

i saw a belt sander fly, someone plugged it in when the switch was on , it flew but not very far, i think the rotational energy overcame it's thrust and made it crash.