think about this...

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You realize that in your OP, wheel speed = anything, plane speed = 0.

Obv, if the plane isn't moving forward relative to the air, it doesn't take off.



Unless, of course, your plan was to phrase a question with a clear answer, then try to confuse people so you would have a big thread.

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I've said this multiple times now - at no point in this thread did I say plane speed = zero.

I suggest following Patrick's advice and creating a FBD.

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UHHHHHHHHHHH what is your point.

Either the conveyor belt is moving exactly opposite of the plane or it is not.

HOW is the plane moving? I would love to know, so I can throw my engineering degree in the trash.

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This is a plane, not a car.

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NO. It IS a car, because it WONT take off.

This is 100% wrong. Think about going to an airport and getting on the conveyer belt. Which direction should the conveyer belt run relative to the direction you're running so that you go faster?

[Hiding]

Is it possible that the friction from the conveyor belt on the surrounding air creates enough air velocity to give the wings lift?

[mmbt0ne]

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This is 100% wrong. Think about going to an airport and getting on the conveyer belt. Which direction should the conveyer belt run relative to the direction you're running so that you go faster?

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WTF? We are entirely aware that the belt is moving in the opposite direction you want to go. You understand that too right?

NLsoldier owes you $400.

[daryn]

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ok, so I thought I knew how a plane worked, but this thread has me second guessing myself.


I always thought the turbine engines on the plane drew air through them (and past the wings) and out the back, propelling the craft forward. is this correct?

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the propeller/engine/whatever just acts as if it was a hand pushing the plane forward. the air that moves over the wings (providing lift) is just regular air, usually just chilling.

you can look at it both ways.. either the plane is moving through still air or the air is flowing over the still wing. either way the same thing happens

[Shajen]

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I have an urge to do more MS Paint.

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Fire away, Cap'n.

[goofball]

why didn't I find this thread sooner. The whole sum of the forces = 0 so acceleration = 0 is of course right re: the skateboard.

The airplane question is about the simplest question ever. How could a reasonable person think that the wheels spinning is what makes the plane fly? Of course the plane has to be moving relative to the air around it (or the ground if that makes it easier).

[Redd]

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Alright, kids. I'm going to let you in on a little rocket science secret. Prop planes do not generate lift by blowing air over the wings.

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They don't? Do you mean that they don't make lift by blowing the air themselves, or that the airflow across the wings from whatever source doesn't generate any lift?

As for the OP's question, it looks to me like the plane will take off. If there's zero friction in the wheel bearings, they can't exact any forces tangential to gravity on the plane.

So we have a forward force provided by the thrust and that's it, resulting in forward acceleration. The runway can move at whatever speed it wants, and the wheels will spin faster but they can't apply that force to the plane. In this particular example, the wheels will just spin with twice the angular velocity than they would with a fixed runway.

It's very much like a float plane taking off from the water (where there's also negligible friction).

[Slow Play Ray]

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Let the system be the fan/board/block. There are no net external forces acting on the system. Thus, the system doesn't move.

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my, that was easy. go umass!

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Hey, why is my answer no good? I am UMass as well, damnit!

*Edit* The reason I said it would go backwards as pictured is because that block is not big enough to "catch" all of the wind from the fan. Hence the "perfect sail" statement.