It's also possible that Godzilla or King Kong might reach down and just hold the plane in place.

it's all ball bearings these days!

and he could grab it by the husk.

Just before the Jet lifts off due to sufficient air movement over the wings in one direction, the conveyer will be moving equally fast in the other direction and the tires will explode due to spinning twice as fast as they are designed and destroy the underside of the plane causing a fiery crash. (e.g. the Concord).

So, the correct answer is that the plane will take off, followed quickly by a crash, followed even more quickly by lawsuits.

That is the difference between physics and engineering.

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Well, not if the wheels are frictionless. I understand the concept that the wheels do not create the forward locomotion on a plane.

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I stated in an early thread that initiall it was possible for the plane to move backwards until the friction of the wheel bearings is overcome. After that the plane would move forward and then take off.

Insofar as a 'magic' treadmill ... that belongs on one of Tanya's 'Can o worms' threads.

Don't worry, I'm still working on that flux capacitor joke

Old Faithful,

Yer two answer option is valid, in my overrated opinion, when offering up assumptions.

My position is based upon the following from the original thread:

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A plane is standing on a movable runway

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Which I assumed removed aerodynamic factors such as a box, etc.

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Keegan's right... it's all about stating your assumptions.

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Ditto.

If you assume no friction in the bearings, it's like the wheels aren't even there. The jet is connected to the bearings, the bearings to the axle, axle to the wheel, wheel to tire, and tire to ground. There is some degree of friction or structure in every connection. If you remove the friction between any two parts, everything below it is moot.

In short, you might as well cut off the landing gear, fire up the engines, drop the jet from a C-130, and have it fly over a rotating treadmill. As the jet flys over the treadmill, there is no friction between the two, therefore the treadmill won't keep the jet from flying on.

I was wrong before, and Keegan is right: "It's all about stating your assumptions.".

The jet flys.

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If you can read this, thank a teacher.
If you can read this in English, thank a Soldier.

i cant believe yall have been arguing about this for this long. who the hell cares?

Somebody say something?

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After that the plane would move forward and then take off.

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Again here is the kicker, IF the plane with the conveyor belt was still stationary compared to the rest of the world and the air it WOULD NOT take off, but the moment you say it moves forward (which it would) it would mover relative to the air around it and cause lift and take off

We are agree in principal But I am taking it one step more. The point is is that even with the conveyor belt and frictionless wheels and such the plane would WANT to move forward. If the plane was kept stationary, no lift is produced. If the plane was allowed to move,(even with the belt) it would cause enough lift and take off.

[This message has been edited by Old Faithful (edited 11/30/2006 2:47p).]

The plane will fly if you assume:
- The treadmill does not apply enough frictional force to keep the plane from reaching the necessary speed relative to the surrounding air to achieve lift
- The tires are not destroyed before terminal velocity is reached

Old Style,

I appreciate yer expertise and sage comments but the phrase:

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If the plane was kept stationary,

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Implies a factor being introduced that is not part of the original hypothetical situation.

But of course I take things quite literally which is not a necessarily a good thing.

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quote:
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Keegan is the one who is really right here, though. The whole f-in thing would quickly explode.
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No, Keegan is an idiot for failing to let his imagination handle a purely theoretical problem and focusing on the non-important mechanical aspects.

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Keegan gave his response in both ways, using his imagination first by interpreting the intention of the question. He then broke it down as an engineer would realizing that the question, as well as assumptions, were not clearly defined and as stated, the whole system would spin out of control.

There are so many questions, brainteasers, etc. like this where the gotcha is in the wording, so it isn't a fallacy to break it down as Keegan did. For some people, "the plane will fly" is the immediate obvious answer, and since it's a brainteaser, they start breaking it down and over analyzing, thinking their obvious answer (though the correct one by the intention of the question) can't be correct.

I've noticed with arguments like this, the people that are correct aren't nearly as adamant as the people who are wrong. The people on the right side are more like "plane will fly, next question". The Monty Hall question is another perfect example of this.

So, if you see idiots on the internet arguing about something like this, pick the side that is less passionate about their deduction.

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Implies a factor being introduced that is not part of the original hypothetical situation.

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I agree but I assumed it was because of the badly worded question.

It will fly with cclearmans statements.


Now onto the lift issue, it is CHANGE of MOMENTUM not the results of a difference in pressures on the top of the wing and the bottom

But ....

Will it take off?

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Now onto the lift issue, it is CHANGE of MOMENTUM not the results of a difference in pressures on the top of the wing and the bottom

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It's really a matter of semantics.

[This message has been edited by IIIHorn (edited 11/30/2006 2:55p).]

ttt

god dammit let it die.....just LET IT DIE

it has reached the point that people that are stating the wrong answer (and don't even understand the question or the fact that the plane still moves) are calling the people with the right answer complete morons.

Do not let my thread die! I trying for a record here.

So, what are the tires made?

Pixie dust, apparently.

http://www.texags.com/main/forum.reply.asp?topic_id=574344&forum_id=12

I'm not sure this has been beaten completely to death so...


ttmft

THIS THREAD IS GREAT!

The best part about this thread are the people that completely disregard reality and factual proof.

STFU!!!!

I have been ignoring this thread, hoping it would just go away.

But sheet! Enough is enough! Who freakin cares! It will fly, it won't. Give it a rest!



UNITY!

Thread of the Week.

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true that

and i thought a simple yes or no answer would end this thread

I think a mathematical proof is in order.

Assume that Friction has a first-order relationship to the force applied in the forward direction (granted, Friction, especially rolling friction, is a higher order interaction).

The Jet has a mass of M. The Engines apply a force F in the Forward (X) direction. The Corresponding Frictional Force (Ff) is applied in the Reverse (-X) direction.

Ff=Z*F, where Z<1

So the sum of total forward forces:
F(total)=F-Z*F=F*(1-Z)

Remembering that Z<1, F(total) will be a positive force in the X direction.

Therefore the plane will move forward.

Now to determine if the plane will take off:
Assume that the runway is a length D.

Force*Distance=Kinetic Energy=1/2 M*v^2

F(total)*D=1/2 M*v^2

(1-Z)*M*a(engine)*D=1/2 M*v^2
(1-Z)*a(engine)*D=1/2 v^2

So if the Engines are capable of providing enough acceleration, and friction isn't too great, and the runway is long enough, then the plane will be able to achieve enough forward velocity to take off.

Even if Z increases as the conveyor belt speed increases, Z won't =1, and the plane will reach a limit where its engines can't produce any more forward force, thus fixing it's forward velocity (because Air Friction becomes a significant factor). As long as the terminal forward velocity is great enough, the plane will take off. But there will be a positive forward velocity.


[This message has been edited by SolidT05 (edited 12/2/2006 10:35a).]

Very nice, Solid. I read through this whole thread thinking why didn't someone just explain it using sum of forces? If the engines have enough thrust to overcome the friction of the wheels up to the takeoff velocity, then it takes off.

Also, don't really understand whoever said Bernoulli's Principle isn't why aircraft fly. Change in momentum of the air describes the same thing...

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The best part about this thread are the people that completely disregard reality and factual proof.

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Like the 'reality' of a massive conveyer belt that can accelerate nearly instantaneously to incredibly fast speeds?

Well ... Will it?

no, it won't.

wait, yes, it will.