Plane on a Conveyor Belt

[TourSpoon]

haha. Goodness. I don't mean laugh, but you need to read carefully - the fact that a plane is on a treadmill (a very long treadmill - a runway length treadmill) will NOT prevent the plane from moving forward. It doesn't stay still or even appear to stay still.

It is entertaining...

Once the plane has thrust, it will pull forward through the air. The wheels spinning on the treadmill has no effect because the air thrust is independent of the wheels/treadmill activity. Got it?

[iacas]

heh. maybe the thread should be locked - although it is somewhat entertaining.

That's why I haven't locked it. People still want to argue with physics, common sense, and the simple fact that the plane takes off.

Dude, I still think your logic is totally off. Air has to be moving over and under the wings of the plane in order to generate the lift necessary for the plane to pull itself into the air. If the treadmill is matching the speed of the plane, as you said, and it appears to be still to observers, then it is not generating air flow over the wings.

It doesn't appear still to observers.

The propulsion of the plane, whether it is jet of prop, is also irrelevant. The engine only provides thrust, which you have already stated is inversley matched by the treadmill.

First off, Speed != Thrust.

Second, the plane's thrust is against the air. The conveyor belt's "thrust" (if you want to abuse a term so it "fits") is against the ball bearings in the wheels of the plane. One is a good big bigger than the other's. Guess which?

For the life of me, I can run as fast as I can on a treadmill, but there is still no breeze hitting me in the face.......

A plane doesn't push against the ground with its wheels (as you do with your feet). Strap a rocket on your back, rollerblades on your feet, and you'll get closer to the truth of this situation.

And don't believe everything you read on the internet, all the pages on this subject are no different than this one. They're all just speculation.

No, they're not - they're based on physics and real-world tests that prove the plane will take off.

[sonicblue]

I'll shoot for an explanation that might work. Imagine that the plane (on the treadmill) is completely "off." Turn the treadmill on. What happens? The plane would move backwards, yes? The wheels would not turn, it would just move along the treadmill like a person standing still on one would.

Now, imagine the same but that there is a wall directly against the tail of the plane, and turn the treadmill on now. Well, clearly the plane can't go backwards, it's against the wall BUT its wheels will definitely start turning. Agreed? Ok next step:

Plane on treadmill, no wall, BUT the thrusters are on a "medium" amount. By that, I mean, the thrusters are on just enough to hold the plane still. The thrusters can do just what the wall did, which is create an air pressure behind the plane that can hold it still. Once you buy that, you can see that they are capable of doing even more, which would be to generate enough force to propel the plane forward.

[TourSpoon]

I like the rocket and rollerblades example. For some reason I have a feeling that the rocket would say "ACME" on it and Wile E. Coyote would be our test pilot.

[g-funk13]

This one time my brother and I super-glued a quarter to the floor in the mall. It was so fun to watch people try harder AND HARDER to get that damn quarter!

[srjorion]

Just yesterday a fellow pilot and I were talking and he made a joke about this question. He's not a member here but we had both seen this before. When I mentioned how some people actually think the airplane doesn't fly, he cocked his head like a dog looking at the answering machine. It turns out he thought the plane didn't fly too!

After a few minutes of me explaining he finally agreed it would fly. Of course, like about 90% of the "NO" people out there he didn't read the full question and made some very wrong assumptions.

[chumdawg]

The way the question is posed, the runway is engineered to move exactly as fast as the wheels turn. So this talk of the wheels turning twice as fast as the runway moves runs afoul of the hypothetical.

The hypothetical asks if an airplane could thrust forward and ultimately take flight in a frictionless environment at the wheels. Obviously a large enough rocket could do it, since we have managed to send space shuttles into flight at ninety degrees to the horizontal, overcoming 100% of the force of gravity. Whether a jet airplane could do it is far from obvious.

If the hypothetical is taken at its word, the feat is exactly the same as an aircraft hovering in air and then achieving flight. It's possible, yes, but there is no commerical aircraft that can do it.

[iacas]

The way the question is posed, the runway is engineered to move exactly as fast as the wheels turn.

No, it moves as fast as the PLANE moves.

The hypothetical asks if an airplane could thrust forward and ultimately take flight in a frictionless environment at the wheels. Obviously a large enough rocket could do it, since we have managed to send space shuttles into flight at ninety degrees to the horizontal, overcoming 100% of the force of gravity. Whether a jet airplane could do it is far from obvious.

Actually, it's incredibly obvious. The plane takes off normally.

If the hypothetical is taken at its word, the feat is exactly the same as an aircraft hovering in air and then achieving flight. It's possible, yes, but there is no commerical aircraft that can do it.

You are wrong.

Sorry I'm so short, but the answer's been explained tens of times before.

[DirtCheap]

The way the question is posed, the runway is engineered to move exactly as fast as the wheels turn. So this talk of the wheels turning twice as fast as the runway moves runs afoul of the hypothetical.

So I guess planes just "hover" when they fly over a moving river.

[mikelz]

I know the answer to this, but I wanted to put it out there as a brain teaser to the rest of you. Just answer the question with a "yes" or "no" - do not give explanations for your answer.

I'm saying no.

[TourSpoon]

This thread is like deja vu all over again...

[TourSpoon]

or Groundhog Day...

[DirtCheap]

and after pages of explainations, there are still those who believe that planes cannot fly over moving objects.

[TourSpoon]

News Flash...The Earth is spinning over 1,000 miles an hour at the equator...

http://geography.about.com/library/f...zearthspin.htm

OMG!

What happens if the conveyor belt is placed on the equator and the plane is positioned so that earth spins directly under it...and there is a lunar eclipse...and volcanic activity...and the captain passes out and the inflatable co-pilot has to take over...and the stewardess has to blow him up...I picked the wrong week to stop sniffing glue...Where is the freakin Elmers? AHHHHHHHHHHHHHH!

[Eore]

Calm Down!!!

[TourSpoon]

News Flash...The Earth is spinning over 1,000 miles an hour at the equator...

The plane still takes off...

[chumdawg]

If the plane were tethered to a building, would it take off? Of course not. It needs relative ground speed. To achieve relative ground speed it needs friction. If there is no friction at the wheels, it never gains relative ground speed.

This is really not that complicated. If the hypothetical is taken to mean that the wheels never gain any traction on the fast-as-it-needs-to-be treadmill, then you don't get flight.

[TourSpoon]

If the plane were tethered to a building, would it take off? Of course not. It needs relative ground speed. To achieve relative ground speed it needs friction. If there is no friction at the wheels, it never gains relative ground speed.

Actually the wheels don't have anything to do with it. Planes don't get their thrust or forward movement from their wheels as it comes from the prop/jet engine. That is the whole point.