Quote :

"The whole idea of the myth is to see if a plane can take off while staying in one place, hence the treadmill."

Actually, you've just interpreted the intent of the myth wrong. Hence why we were discussing the importance of the way the question is worded.

1/28/2008 9:34:49 PM

Quote :

"Stationary planes do not fly . . . are we really even having this discussion?"

If the engines are running how is the plane going to stay stationary?

Because the treadmill wouldn't stop it, hence the myth/discussion.

1/28/2008 9:36:29 PM

Quote :

"The whole idea of the myth is to see if a plane can take off while staying in one place, hence the treadmill."

no it isn't. idiot.

1/28/2008 9:38:18 PM

This is . . . really sad. Are you guys serious? You aren't actually arguing about the result of the myth, you are arguing what the actual myth is?

This is like a bad game of telephone.

1/28/2008 9:54:42 PM

Well, those of us left in the thread aren't dumb enough to misunderstand basic laws of physics and aerodynamics... so we all know what will happen given each potential scenario.

The only issue is/was that we don't know who originally posed the question, and thus we don't know the parameters of the myth, which is why so many people misunderstood the question and gave the answer that seemed "wrong".

[Edited on January 28, 2008 at 9:56 PM. Reason : aren't]

1/28/2008 9:56:46 PM

There is no misunderstanding the question

Because the 'myth' isn't remotely interesting unless the treadmill is matching the speed of the plane and keeping the plane stationary. In that scenario, a basic understanding of physics lets you know exactly what will happen but your intuition makes you want to think that the plane will take off.

Any other scenario isn't nearly as interesting as we all know that there isn't a plane on the planet that couldn't out accelerate a treadmill, and gain lift. Hell, a human being can accelerate faster.

Stop trying to cover for people that went with their gut instinct instead of analyzing what really would happen.

1/28/2008 10:03:21 PM

Not trying to. You might not realize, but there are people out there (and people previously involved in this "debate") who think that the plane's forward motion on take off comes from propulsion generated by the wheels, completely neglecting the fact that planes have engines.

1/28/2008 10:07:40 PM

Quote :

"Because the 'myth' isn't remotely interesting unless the treadmill is matching the speed of the plane and keeping the plane stationary."

The treadmill can't keep the plane stationary is the whole point. There is no testable scenario where the plane would have its engines on, but still actually be stationary.

1/28/2008 10:10:21 PM

yes there is.... as soon as the plane starts to move forward, someone speeds up the treadmill so that it negates the forward motion...the plane stays stationary and doesn't take off...

the myth states that the speed of the treadmill is increased to match the net forward motion of the airplane....

so as the plane moves forward, they crank up the treadmill and it counteracts the plane

i don't care what causes the plane to move forward, i know the wheels don't do it..i know it is thrust from engines...but that thrust causes it to move forward down the runway, in this case the treadmill..
so if you crank that treadmill up to counteract the forward motion, the forward motion will stop

[Edited on January 28, 2008 at 10:16 PM. Reason : yep]

1/28/2008 10:15:36 PM

Quote :

"yes there is.... as soon as the plane starts to move forward, someone speeds up the treadmill so that it negates the forward motion...the plane stays stationary and doesn't take off... the myth states that the speed of the treadmill is increased to match the net forward motion of the airplane.... so as the plane moves forward, they crank up the treadmill and it counteracts the plane "

Case in point of someone who thinks a force acting upon the wheels is going to influence the motion of the plane. (nevermind, he corrected himself... but still doesn't seem to understand the parameters)

Anyway, to answer your post, refer to the earlier analogy of someone wearing roller skates on a treadmill and being pushed by someone not on the treadmill.

If you're thinking that the treadmill could move quickly enough to use rolling friction to counteract the thrust of the plane, then you're right, it technically could, but it's entirely implausible and not the intent of the original myth.

[Edited on January 28, 2008 at 10:20 PM. Reason : .]

1/28/2008 10:18:11 PM

as long as that plane is attached to the wheels, and the wheels are attached to the ground, then the wheels play a factor...


the plane starts moving forward, then crank the treadmill up so that it quits moving forward


^that's what i'm thinking..
the myth i heard stated "the speed of the treadmill is increased to counteract any forward movement of the plane"

[Edited on January 28, 2008 at 10:20 PM. Reason : indeed]

1/28/2008 10:19:57 PM

I can see how the engines cause thrust that would move the plane forward regardless of the treadmill. I don't think the myth is even possible to do. if someone is on roller skates on a very fast treadmill all someone has to do not on the treadmill (engines) is produce enough force to counteract friction from the Rollerblades (not very much force) so the engines would easily push the plane forward. not gonna stay still.

1/28/2008 10:21:43 PM

^^



What about snow planes? or sea planes then? They don't have wheels.


[Edited on January 28, 2008 at 10:28 PM. Reason : a]

1/28/2008 10:28:21 PM

if they are gonna get a treadmill moving fast enough to counteract the friction of the wheels versus a jet engine that is gonna be one fucking fast moving treadmill

1/28/2008 10:31:31 PM

^ no

It takes even less to push a plane, than it does to push a car in "neutral" gear.

[Edited on January 28, 2008 at 10:33 PM. Reason : ]

1/28/2008 10:32:31 PM

You guys are silly-heads.

1/28/2008 10:34:17 PM

My glider argument was just to show that engine power does not factor in to a plane taking off from a treadmill. Planes can and usually are at or near full power for takeoff's but remain stationary till the pilot releases the brakes.

Quote :

"gk2004 is such a fucking troll"

Nope, just trying to get my point across. What I do know is that planes dont fly without air flowing over the wings Even on a treadmill that is moving at 100 mph no air is moving over the wings therefore no lift will be generated.

Perhaps I will be proven wrong on Wednesday.

1/28/2008 10:36:44 PM

^^^Exactly... which is why he's correct that the required treadmill speed to make rolling friction counteract the engine thrust on the air would be absolutely obscene.

Rolling friction (RF) is nearly negligible. Engine thrust (ET) is very large. To make RF = -ET, the speed of the treadmill would be potentially faster than the speed of light (Just an assumption for dramatic effect... I didn't actually do the math and I don't plan to).

[Edited on January 28, 2008 at 10:40 PM. Reason : .]

1/28/2008 10:37:44 PM

Quote :

"as long as that plane is attached to the wheels, and the wheels are attached to the ground, then the wheels play a factor... the plane starts moving forward, then crank the treadmill up so that it quits moving forward ^that's what i'm thinking.. the myth i heard stated "the speed of the treadmill is increased to counteract any forward movement of the plane" "

no, jesus. you guys fundamentally just don't get it.

the treadmill can go as fast at it want. It can go at 10,000 mph if it wants, and as long as the wheels and wheel bearings on the plane don't burn up because of high RPMs and heat generated, it will still have no theoretical impact on the forward movement of the plane that is generated from the thrust of the engines.

as discussed earlier, if the myth is stated as "the speed of the treadmill is increased to counteract any forward movement of the plane", then the myth is based on a false premise, and therefore the myth is neither true nor false because the premise is impossible to begin with.

[Edited on January 28, 2008 at 10:42 PM. Reason : .]

1/28/2008 10:40:53 PM

^^ I see, i read it wrong.


DAMMIT first time i've been wrong in this thread

BUT, you'd have to reword the question because the plane would have already taken off by the time it reached this speed. So the treadmill would have to be defined as moving at maybe 100x the plane's speed.

[Edited on January 28, 2008 at 10:41 PM. Reason : ]

1/28/2008 10:41:32 PM

The only version of this proposal that is interesting is if it is worded to say the treadmill will match the speed of the wheels, not the speed of the plane.

We then make the following assumptions:
-friction in the wheel bearings is non-zero
-wheels will maintain static friction contact with treadmill
-this treadmill is able to move at unrealistic speeds without damage
-any speed means 'speed relative to the ground', both translational and rotational

Under this scenario, two things could happen.
1- your landing gear will break as the treadmill accelerates to unrealistic speeds to match wheel speed relative to earth, at the same time trying to generating a translational force equivalent to the force generated by the thrust
2- if you make a further assumption that your landing gear is unrealistically sturdy, then the plane would actually flip and crash on its nose as there would eventually be a net rotational force large enough to overcome the force due to gravity

There is only one scenario (in the theme of the original problem) where the plane would not take off, requiring the following assumptions:
-friction in the wheel bearings is non-zero
-wheels will maintain static friction contact with treadmill
-this treadmill is able to move at unrealistic speeds without damage
-any speed means 'speed relative to the ground', both translational and rotational
-landing gear (and the rest of the plane for that matter) is unrealistically sturdy
-an additional rotational force is applied by some means to the plane to cancel the net rotational force of the thrust and wheel bearing friction

the end.

1/28/2008 10:51:51 PM

Quote :

"he only version of this proposal that is interesting is if it is worded to say the treadmill will match the speed of the wheels, not the speed of the plane."

If the plane is moving forward due to the engines, then the treadmill speed is going to be doubling speed infinitely, since it invokes the A = A + A paradox.

1/28/2008 10:54:33 PM

can't bust or prove this... no treadmill can go that fast.

[Edited on January 28, 2008 at 10:57 PM. Reason : .]

1/28/2008 10:54:38 PM

Quote :

"The only version of this proposal that is interesting is if it is worded to say the treadmill will match the speed of the wheels"

That's not a realistic situation.

1/28/2008 10:55:35 PM

Quote :

"The force is on the air, not the treadmill. It will fly."

1/28/2008 10:58:51 PM

Quote :

"can't bust or prove this... no treadmill can go that fast."

you can prove or bust this.... with simply physics and logic

1/28/2008 11:00:08 PM

Quote :

"If the plane is moving forward due to the engines, then the treadmill speed is going to be doubling speed infinitely, since it invokes the A = A + A paradox. "

I am aware of that. That does not apply to my scenarios.

Quote :

"That's not a realistic situation."

I am also aware of this. There is no realistic situation involving a giant treadmill and a plane.

[Edited on January 28, 2008 at 11:04 PM. Reason : .]

1/28/2008 11:01:24 PM

Quote :

"I am aware of that. That does not apply to my scenarios."

You said...

Quote :

"The only version of this proposal that is interesting is if it is worded to say the treadmill will match the speed of the wheels"

This is actually the least interesting version, because it's the one that can't be tested.

1/28/2008 11:19:03 PM

Quote :

"This is actually the least interesting version, because it's the one that can't be tested."

Any scenario of this problem that can actually be tested is boring, because anyone who has taken basic physics should be able to predict what will happen.

My scenario required at least a small amount of thought, which is why it was more interesting.

1/28/2008 11:24:11 PM

While watching a treadmill rapidly increase it's speed to infinity might be fun, it's not actually possible.

1/28/2008 11:25:09 PM

^ exactly

in the scenario ^^ stated, the treadmill will never actually reach the wheel speed, only approach it asymptotically.

I guess whether this is interesting is in the eye of the beholder.

To me, the intriguing factor is watching the won't-flyers back pedal when the plane actually flies.

[Edited on January 28, 2008 at 11:27 PM. Reason : ]

1/28/2008 11:26:37 PM

Quote :

"While watching a treadmill rapidly increase it's speed to infinity might be fun, it's not actually possible."

That doesnt happen in the scenario I have described. It would be unrealistically fast, but not infinity.

Quote :

"in the scenario ^^ stated, the treadmill will never actually reach the wheel speed, only approach it asymptotically. "

Thats not true actually, and doesnt even make sense in the context of this scenario anyways, since it was already stated the treadmill would match the wheel speed. Its pretty obvious in this scenario the system would reach a steady state, with treadmill exactly equal to wheel speed.

1/28/2008 11:37:35 PM

^ No, it won't, not if the engines remain powered on. Because the plane will continuously accelerate until it takes off, where the wheels will no longer have contact with the treadmill.

In the intermediary time before the plane takes off, the treadmill can't actually match the speed of the wheels, because the speed of the wheels is a factor of the treadmill AND the airplane.

The treadmill can only match the speed of the plane itself.

[Edited on January 28, 2008 at 11:40 PM. Reason : ]

1/28/2008 11:40:23 PM

Oh ok, now I see why you dont understand. The plane does not accelerate. The net translational force is zero. Read the original post again I bet you'll get it.

[Edited on January 28, 2008 at 11:45 PM. Reason : .]

1/28/2008 11:45:36 PM

Quote :

"since it was already stated the treadmill would match the wheel speed. Its pretty obvious in this scenario the system would reach a steady state, with treadmill exactly equal to wheel speed."

false premise.
just because you say something is true or will happen - that the "treadmill would match the wheel speed" - doesn't mean it's actually physically possible. You're basing your conclusion ("the system would reach steady state") on a premise that is not possible to begin with, therefore your conclusion is invalid

1/28/2008 11:47:39 PM

^^No, you don't get it.

If the treadmill is actually moving, and the friction in the bearings is non-zero, then the treadmill CANNOT match the speed of the wheels, EVER.

[Edited on January 28, 2008 at 11:48 PM. Reason : ]

1/28/2008 11:48:13 PM

If A is treadmill speed, B is wheel speed, and C is the function of plane speed that influences wheel movement.

Treadmill speed matches wheel speed:
A = B

Wheel speed is a function of the treadmill speed and the plane's speed:
B = A + C

Can you not see how this creates a paradoxical, impossible scenario?
B = A
B = A + C

Unless C = 0, which cannot happen with the plane's engines on, this situation is impossible.

1/28/2008 11:53:55 PM

Quote :

"false premise. "

OK well you either didnt read the original post or did not understand it. Yes, a number of things in the scenario were not realistic. That does not invalidate the conclusion. If you accept the assumptions made in the original post the conclusions are valid.

Quote :

"If the treadmill is actually moving, and the friction in the bearings is non-zero, then the treadmill CANNOT match the speed of the wheels, EVER."

Do you have any logic to explain this? There is no reason the treadmill speed could not match the wheel speed in this scenario.

Quote :

"Can you not see how this creates a paradoxical, impossible scenario? B = A B = A + C Unless C = 0, which cannot happen with the plane's engines on, this situation is impossible."

Of course I saw that, a long time ago. This scenario results in a C equal to zero. Read the original post, you will get it.

[Edited on January 28, 2008 at 11:59 PM. Reason : ]

1/28/2008 11:54:23 PM

didnt mean to double post

[Edited on January 28, 2008 at 11:58 PM. Reason : ]

1/28/2008 11:57:15 PM

Just because you say something is true does not make it unconditionally true.

Watch...

"Given the scenario x*2=y, we need to find y. Assuming that x=1000, and assuming that y=100, my situation is logical and yours is not."

1/28/2008 11:59:53 PM

after it works, i bet adam and jamie will do something retarded to see if they can prevent the plane from taking off. like weld the plane to the conveyor rails or rotate the wings 90 degrees.

1/29/2008 12:07:14 AM

a fighter jet could take off stationary relative to the ground on a treadmill.

but those can also take off from a standstill without the treadmill.

1/29/2008 12:14:45 AM

Quote :

""If the treadmill is actually moving, and the friction in the bearings is non-zero, then the treadmill CANNOT match the speed of the wheels, EVER." Do you have any logic to explain this? There is no reason the treadmill speed could not match the wheel speed in this scenario."

Okay, let's let V represent the speed of the plane, W represent the rotational velocity of the plane's wheels, and T represent the treadmill's speed.

Quote :

" The only version of this proposal that is interesting is if it is worded to say the treadmill will match the speed of the wheels, not the speed of the plane."

So you are saying that T=W right?

And W=V+T

if you substitute T for W

you're saying

W=V+W

And if the plane is moving, then V>0. If the plane's engines are powered on, then V WILL be greater than 0. And if V>0, then T>0 always. And since W=T by your premise, then W>0 also.

So logically/mathematically, your conclusion that W=V+W is logically flawed.

1/29/2008 12:47:40 AM

What if the plane is landing on a treadmill?

1/29/2008 9:47:43 AM

Again, i cant believe this discussion is going on.

Try this at home:

1. Push a treadmill with the rear of it close to a wall. The wall in this example represents the standing air around a airplane sitting on the runway.

2. Put on rollerskates (or stand on a skateboard) and get on the treadmill facing the wall. You now represent an airplane sitting on the runway.

3. Push your arms against the wall with light force. Congratulations, you have just turned the engines in the plane on.

4. Have a friend start the treadmill, while you still apply force to the wall. The treadmill is now moving.

5. To complete the experiment, have your friend change the speed of the treadmill as much as he/she wants, and use the force of your arms (engines) to move yourself forward and backward on the treadmill. Push really hard (cranking up the engines) and move yourself on the treadmill. Congratulations, if you pushed hard enough, you took off.

If you have really good bearings in your skates, the force of the friction will be negligible, and you will require almost the same amount of pushing from your arms to keep you in the same spot on the treadmill regardless of the speed of the treadmill.

Does this help?

I dont have any rollerskates/skateboard or I would make a video of this in action.

[Edited on January 29, 2008 at 10:51 AM. Reason : ,]

1/29/2008 10:49:35 AM

this thread is hilarious.

people that have no clue and the people that "get it" are equally entertaining

1/29/2008 10:52:30 AM

^^BUT THERE ISN'T AIR GOING OVER THE WINGS MEANING THAT THERE ISN'T LIFT!!!!!!!!

1/29/2008 11:08:47 AM

damn some of you really have no concept of physics. YES THE PLANE WILL TAKE OFF!! air will move over the wings as the plane moves down the treadmill (granted the treadmill will have to be as long as a runway) until the plane reaches a speed at which the air moving over the wings creates enough lift to pick the plane up off of the treadmill.

i think too many of you are stuck on the idea if the treadmill matching the speed of the wheels. so take the wheels out of the equation, put skis on the plane as landing gear and cover the treadmill in snow...can you visualize it yet?

1/29/2008 11:19:48 AM

(I was being sarcastic)

1/29/2008 11:31:25 AM

Quote :

"YES THE PLANE WILL TAKE OFF!! air will move over the wings as the plane moves down the treadmill (granted the treadmill will have to be as long as a runway) until the plane reaches a speed at which the air moving over the wings creates enough lift to pick the plane up off of the treadmill. i think too many of you are stuck on the idea if the treadmill matching the speed of the wheels. so take the wheels out of the equation, put skis on the plane as landing gear and cover the treadmill in snow...can you visualize it yet? "

No, retard.

Nobody is arguing that a plane accelerating down a treadmill won't be taking off.

The myth is whether the plane can take off if its remaining at a standstill with engines at full throttle.

Thats the point of a treadmill in the first place, allowing you to move at speed without having any velocity.

1/29/2008 11:44:12 AM