4

11/7/2007 10:48:39 PM

yes hooksaw that is what i meant. Sorry it took so long to get back to this topic.

11/8/2007 12:48:50 AM

i am still curious about this treadmill, and whether or not i can run on it.

11/8/2007 8:52:10 AM

you won't take off on it

11/8/2007 9:06:15 AM

what the hell..

i mean, clearly i have thrust, same as a plane.

i fart.

what is the difference here?

11/8/2007 9:07:01 AM

http://www.mercurynews.com/food/ci_7320206

looks as though mythbusters is going to air this on Dec. 12

didn't know if this has been posted, or even true, i hope it is

i'm still undecided on whether it lifts of stays stationary after reading a bunch of others explaining its going to stay in place. none-the-less, i'm going to tune in....

my vote: its not going to fly.

11/19/2007 12:23:32 AM

i don't mean to be a dick, but there's no voting about it. it isn't a "maybe" scenario. it will take off.

11/19/2007 12:24:42 AM

wat

11/19/2007 12:27:08 AM

no, i'm not going to take that as being a dick, but let me try to explain what i read another guy say on the net.

he was saying look at the wheel in a short amount of time. assuming no slip say the plane moves one rotation forward (12 inches), well, the belt is going to push it backwards (the same 12 inches). i understand the thrust is going to push it, but if the wheels don't slip on the belt, the plane will not move forward.

i mean, i hate sounding like a dumbass but it just makes sense to me that its not moving. and no, i'm not trying to troll this.

11/19/2007 12:29:55 AM

imagine you're on a treadmill in a big room

and you have a friend in front of you who's not on the treadmill

and there's a rope tied between you

and you both start running when the treadmill starts

11/19/2007 12:32:11 AM

Imagine a guy wearing rollerblades on a treadmill.
now imagine him holding onto a rope that is tied to a wall in front of the treadmill
crank that treadmill up to 100 mph
the wheels will spin super fast, but it takes virtually no effort to not move and the guy can easily pull himself forward on the treadmill.

11/19/2007 12:33:38 AM

^^nobody moves???

^it would take alot of effort, because as the person on rollerblades tries pulling, the treadmill will speed up, keeping him stationary??

i don't know, i'm just going to give up. i'm really not trying to argue with anyone, cause i just can't wrap my static brain around this dynamic question.....



[Edited on November 19, 2007 at 12:37 AM. Reason : .]

11/19/2007 12:33:43 AM

you move

11/19/2007 12:34:09 AM

just watch the video on the previous page. stuttering dialogue aside.

[Edited on November 19, 2007 at 12:36 AM. Reason : ,]

11/19/2007 12:34:40 AM

so it's harder to keep the plane straight

?

11/19/2007 12:36:13 AM

this just in:NutGrass is a fucking idiot

11/19/2007 12:36:31 AM

yeah,


god damn

11/19/2007 12:40:02 AM

holy shit are you morons still arguing this

it will NOT TAKE OFF. if it does, it's because the props generated airspeed over the wings, or because there was air moved by the QUARTER MILE LONG CONVEYER BELT

11/19/2007 12:41:33 AM

11/19/2007 12:41:47 AM

stfu, walter

i said i didn't want to argue about the question, i'm just saying that the show will air on dec. 12 and i will be proven wrong.

11/19/2007 12:43:03 AM

i really can't wait for the mythbusters episode to end this thread.

11/19/2007 12:43:37 AM

it shouldn't even take a mythbusters episode

just a little (somewhat)critical thinking

11/19/2007 12:45:46 AM

it's funny how militant some of the people are that think it won't take off. I don't fault Nutgrass because he admits he doesn't know enough about it, but damn...some of you really ought to realize you really don't know what you're talking about.

11/19/2007 12:48:10 AM

ya know, the military already figured it out...

11/19/2007 12:50:25 AM

anyone still want to bet money against me?

[Edited on November 19, 2007 at 12:51 AM. Reason : ^that's not the same scenario. ]

11/19/2007 12:50:51 AM

it could work!

11/19/2007 12:52:50 AM

^^nah, no money on this one...

however, i could send you to a couple other message boards and you may find a taker. some guys are positive, without a doubt, that it will not take off.

[Edited on November 19, 2007 at 12:54 AM. Reason : .]

11/19/2007 12:54:15 AM

I'll throw in with Duke against anyone who wants to bet it won't take off

PLEASE, accept this challenge. I'm broke.

11/19/2007 12:54:25 AM

ya gotta understand that
A) the treadmill would be longer, of course
B) the belt direction would more the jet forward if the jet were not running.
C) no, it isn't gonna just rise up in the air...i know that.

11/19/2007 12:56:37 AM

suppose you have a jet on a long treadmill, but the jet has no engines. it's just sitting there, nothing's moving.

now suppose you tie a rope to the jet and some guy standing off the runway starts pulling it forward. the plane moves forward, and the treadmill rotates at the same speed in the opposite direction. plane is still moving forward though, because he's pulling it.

now suppose that man is actually standing behind the plane, off the runway, pushing it forward with a long stick. still moves forward, right?

now suppose that man is not a man at all but a jet engine, pushing that stick forward with the same force the man did with his legs.

now suppose we shorten that stick, so much so that we might as well just assume the jet was built with the engine.

has anything changed? no...the plane still moves forward, and will accelerate as normal until it lifts. let the treadmill spin opposite to its mechanical heart's content, all that'll do is make the wheels roll faster until the plane loses contact with the ground.

I REALLY don't know how to break it down any simpler, but if you still disagree, let's put $100 on it.

11/19/2007 1:05:21 AM

the problem is that people are confusing how the forces are transferred.

First think about a person walking / running on a treadmill. In normal walking the person's motion comes from the friction reaction with the floor. So now the floor is moving with the same speed, but in the opposite direction of the person's motion. The result is that relative to the floor, the person does not move.

Next think about a person on a bike. Under normal circumstances the force is transferred from the person through the pedals through the chain to the back wheel where the friction force propels the bike forward. If the bike is now on a treadmill moving at the same speed in the opposite direction of the bike, the person will be stationary to the floor.

In both cases the person is moving relative to the treadmill, just not relative to the ground.

Now assume that same bike is on a street in NY City and the biker is holding onto a car and is coasting. Can he move himself up the side of the car? Sure . . . it happens all the time. In this case, the force is not being transmitted through his own tires (instead the force is transmitted through the car), yet momentarily he moves faster relative to the ground.

An airplane takes this a step farther. Instead of imparting the force through a "fixed" object, the force is imparted on on the air which is essentially fixed because of the magnitude of the force being applied. So if the airplane is just sitting on a giant treadmill without it's engines running and the treadmill starts to move, what will happen? Well in the perfect world there would be no friction in the bearings, so the plane is going to remain stationary relative to the ground and the wheels will rotate. No matter how fast the treadmill moves, the plan will be stationary to the ground since there would be no force being transmitted between the mass of the plane and the ground.

But the world isn't ideal and there is friction, so we first think about what would happen if the treadmill were to move very slowly. A very low force is applied to the bearings and it doesn't overcome the friction force and the wheels don't rotate and the plane will move. If however, the treadmill moves very fast (assuming it instantaneously becomes fast) then there will be a very large force transmitted to the bearings which will easily overcome the static friction and the wheels will rotate freely. Some very small percentage of the horizontal force will be transmitted will be transmitted through the bearings and cause the plane to move very slowly.

So now think about the plane just sitting on the runway. The brakes are off and the engines are on and the throttle is increased. What happens? The plane moves forward relative to the ground since the engines transmit a force to the air which essentially transmits the force to the ground.

Now put the plane back on the treadmill and throttle the engines. There is a very small force from the friction in the bearings moving the plane backwards and a very large force from the engines moving the plane forwards. The engine force >>>>>>>>>>>>>>>>>>>>> friction force and will easily bring the plane up to takeoff speed.

[Edited on November 19, 2007 at 1:18 AM. Reason : ^what he said. I spent way too much time typing that instead of doing HW. ]

[Edited on November 19, 2007 at 1:28 AM. Reason : typo ]

11/19/2007 1:14:50 AM

duke, a buddy of mine asked for your cell # at one point during our discussion a couple weeks ago when I told him you had 30k dollarbux on it.

he's currently a recovering compulsive gambler, however.

11/19/2007 1:16:33 AM

^^ I'm not a "she," jerk.

[Edited on November 19, 2007 at 1:25 AM. Reason : but well put.]

11/19/2007 1:25:32 AM

I'll just throw my two cents into this. I don't know too much about the subject but . . .

From what I understand the plane's wings are shaped in such a manner that when it is moving relative to the air around it, the air above the wings is moving faster than the air below the wings. This causes less pressure about the wings, forcing an upward motion.

If the plane is moving on the treadmill, it is not moving relative to the air around it. This creates no difference in pressure, resulting in no lift.

People keep saying that it is moving forward, but I just don't see it. It is staying in the same place, the air around it isn't moving, and its velocity and acceleration both equal zero. (Keep in mind this is in an ideal, theoretical situation where the plane shoudl never actually move).

[Edited on November 19, 2007 at 1:33 AM. Reason : .]

11/19/2007 1:28:22 AM

why do you people keep explaining the same thing over and over, its been explained 100 times in this thread alone,

11/19/2007 1:30:21 AM

^^explain why you think it is will not move relative to the ground?


[Edited on November 19, 2007 at 1:33 AM. Reason : ]

11/19/2007 1:32:10 AM

Well, if I understand the circumstances correctly, the plane is moving like a person on a treadmill. They are running, but not actually moving relative to anything around them.

11/19/2007 1:34:57 AM

as i stated like 4 posts up, the person must transmit a force to the treadmill (through his feet) but the plane does not. So the plane is not restricted as a person is.

11/19/2007 1:38:51 AM

[Edited on November 19, 2007 at 1:41 AM. Reason : ]

11/19/2007 1:40:47 AM

everyone keeps saying that the wheels will have to go twice as fast, well the treadmill is going to work twice as fast to keep the plane in the place it first started. for the plane to move forward, it is going to have to gain 'ground miles' or whatever its called, but the treadmill will not allow that to happen. for every 'ground mile' the wheel tries to spin, the treadmill is going to turn it back. i just see it sitting in the same spot.....

as far as the person on a bike getting a push while on a treadmill, i don't see the bike going off the front of the treadmill. i see the treadmill speeding up and keeping the bike in the same spot, no matter how hard his buddy pushes him. now, if the treadmill stayed at the same speed the entire time, sure, the bike will ease off the front while being pushed, but i'm interpreting the question that the treadmill will speed up to keep the bike/plane stationary.

11/19/2007 1:45:19 AM

no

11/19/2007 1:58:39 AM

no, the conveyor can spin the plane's wheels "back" as much as you want...the airplane will still move forward relative to the ground (or more specifically, the surrounding air mass).

btw, i'm willing to bet smaller denominations of money, too...$20, $100, $500, whatever...just gotta settle on terms of how we could authoritatively settle the question, and have a trustworthy middleman to hold your money until I take it.

11/19/2007 2:50:20 AM

The plane takes off, says NFL sunday and miller light.

Also, i think i remember thinking about this, and deciding it would take off

11/19/2007 2:54:41 AM

wait a minute

the treadmill is irrelevant

11/19/2007 7:53:33 AM

Quote :

"The plane takes off, says NFL sunday and miller light"

That's a reliable source, for sure.

11/19/2007 8:18:01 AM

The thing people seem to be getting confused with is what is providing the forward movement speed of the plane. When a plane takes off it is not like a car where the forward motion is being driven by the wheels. On a plane the wheels are basically free moving and forward movement is driven by the thrust of the engine, or the pull of a prop. Therefore no matter what the plane is sitting on it will still move forward at the same speed, all that is going to happen is the wheels are going to spin twice as fast since there are two forces acting on them. If this same thing applied to a car where forward movement was driven by the wheels then yes the car would sit in place.

11/19/2007 9:14:22 AM

Quote :

"didn't know if this has been posted, or even true, i hope it is"

on first page

11/19/2007 9:17:03 AM

hence,

Quote :

"the treadmill is irrelevant"

why has no one just said that

11/19/2007 9:19:58 AM

Quote :

"Well, if I understand the circumstances correctly, the plane is moving like a person on a treadmill. They are running, but not actually moving relative to anything around them."

are you really that fucking stupid? imagine a person with fucking WHEELS ON THE BOTTOM OF THEIR SHOES AND JET ENGINES ON THEIR BACK, they can use almost no energy to stay still because guess what, THEY HAVE FUCKING WHEELS THAT ROLL. The conveyor is essentially wasted energy that at best is going to make the wheels spin around faster, whooptie fucking doo. Now, the jet engine obviously has enough energy to overcome the tiny force pushing the wheels in a backwards (or whatever direction, it doesn't matter, period) direction (and by tiny I mean really really fucking tiny, because wheels roll people, that's why we fucking use them)

Does anybody still not understand this or are yall just trolling that bad? The plane does not use the wheels for anything other than to roll down the runway, a conveyor belt is only going to make them have to move a little faster, it isn't going to cancel out all the thrust from two god damn jet engines or make all the air above the conveyor move at such an insane pace that the plane can't create lift.


[Edited on November 19, 2007 at 9:27 AM. Reason : yea, just ignore the god damn conveyor it has NOTHING TO DO WITH AERODYNAMICS]

11/19/2007 9:26:20 AM

But the treadmill is going backwards to counter the forward roll of the plane.

11/19/2007 9:38:37 AM