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#607410 - 07/11/07 12:38 PM Re: Airplane on a treadmill question
Mobycat Offline
Member
*****

Registered: 12/09/00
Posts: 8374
Loc: the hue of dungeons and the sc...
Quote:
Originally posted by cadams7407:
OMG! does the navy know about this!? Why don't they have treadmills on all the air craft carriers!?!?!?!?!
Bad example there, Leroy.

An aircraft on an aircraft carrier uses a catapult.

The distance a plane takes to take off on land is the same as the distance to take off if there were a treadmill under it.

Put yourself on iceskates. Stand on ice next to a pole. Put flippers on your hands. Now flap like a bird trying to fly forward (not up). You WILL move relative to the pole. Same thing.
_________________________
"Nature has constituted utility to man the standard and test of virtue. Men living in different countries, under different circumstances, different habits and regimens, may have different utilities; the same act, therefore, may be useful and consequently virtuous in one country which is injurious and vicious in another differently circumstanced" - Thomas Jefferson, moral relativist

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#607411 - 07/11/07 12:39 PM Re: Airplane on a treadmill question
GrayHam Offline
Member

Registered: 17/04/01
Posts: 8849
Quote:
Originally posted by Mobycat:
Quote:
Originally posted by cadams7407:
[b]OMG! does the navy know about this!? Why don't they have treadmills on all the air craft carriers!?!?!?!?!
Bad example there, Leroy.

An aircraft on an aircraft carrier uses a catapult.

The distance a plane takes to take off on land is the same as the distance to take off if there were a treadmill under it.

Put yourself on iceskates. Stand on ice next to a pole. Put flippers on your hands. Now flap like a bird trying to fly forward (not up). You WILL move relative to the pole. Same thing.[/b]
He's not getting that the plane's engines are providing thrust, I bet.

I think he's one of the people envisioning a static aircraft on a treadmill . . .
_________________________
Does anybody remember laughter?

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#607412 - 07/11/07 01:30 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


Will the airplane transmission handle the power needed for take-off?

[Wave]

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#607413 - 07/11/07 01:34 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


Quote:
Originally posted by vitaly:
Will the airplane transmission handle the power needed for take-off?

[Wave]
Yes, but it is hard on the diffs.

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#607414 - 07/11/07 01:41 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


The transmission will, but the transfer case will fail, thus they need to install some crawler gears.

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#607415 - 07/11/07 01:44 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


Quote:
Originally posted by GrayHam:
Quote:
Originally posted by Mobycat:
[b]
Quote:
Originally posted by cadams7407:
[b]OMG! does the navy know about this!? Why don't they have treadmills on all the air craft carriers!?!?!?!?!
Bad example there, Leroy.

An aircraft on an aircraft carrier uses a catapult.

The distance a plane takes to take off on land is the same as the distance to take off if there were a treadmill under it.

Put yourself on iceskates. Stand on ice next to a pole. Put flippers on your hands. Now flap like a bird trying to fly forward (not up). You WILL move relative to the pole. Same thing.[/b]
He's not getting that the plane's engines are providing thrust, I bet.

I think he's one of the people envisioning a static aircraft on a treadmill . . .[/b]
Willing to bet he's one of those people that are cornfused and think the engines drive the wheels.

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#607416 - 07/11/07 01:45 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


Quote:
Originally posted by AHTOXA:
The transmission will, but the transfer case will fail, thus they need to install some crawler gears.
Naw, Tony, then the crawler gears will have you blowing axle shafts, especially when reverse is used laugh

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#607417 - 07/11/07 04:22 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


This is so funny to me. That's why I like coming back to it. Some people just can't get past their initial reactions.

Look at Madman's FBD. If you don't understand that, trust those of us that do.

The plane takes off. Period, end of story.

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#607418 - 07/11/07 08:39 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


Quote:
Originally posted by mine_man:
This is so funny to me. That's why I like coming back to it. Some people just can't get past their initial reactions.

Look at Madman's FBD. If you don't understand that, trust those of us that do.

The plane takes off. Period, end of story.
Why should we blindly trust that you understand Madman's FBD (whatever that is :p )?

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#607419 - 08/11/07 07:20 AM Re: Airplane on a treadmill question
Anonymous
Unregistered


FBD - free body diagram, is a pictorial representation often used by physicists to show all contact and non-contact forces acting on the given free body (wikipedia).

Break the object down to the forces present and the answer is obvious. I have not yet seen a FBD presented by the "will not take off crowd".

How often do you get to discuss physics? It's fun, for the nerds of the forum like me. Brings me back to the hundreds of FBDs I had to come up with for physics I and II back in college. Damn some of those were hard; oh the memories...

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#607420 - 08/11/07 12:37 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


Isnt the treadmill going to cancel out the engine thrust?
I mean the debate is a treadmill moving at the same speed as the plane.
If you are running on a treadmill and someone pushes you, yes you will go forward, but not clear across the room.

Engine thrust may cause the plane to go faster than the tread mill, and will just move it forward off the treadmill, if the treadmill does not speed up.

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#607421 - 08/11/07 12:39 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


Die, stupid fucking thread, die!!!!

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#607422 - 08/11/07 07:04 PM Re: Airplane on a treadmill question
Big Daddy Chia Offline
Member

Registered: 12/06/01
Posts: 4442
Loc: Austin, TX
Quote:
Originally posted by AHTOXA:
Die, stupid fucking thread, die!!!!
no
_________________________
Scott "Chia" Holland
"God created man. Sam Colt made them equal"

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#607423 - 08/11/07 08:30 PM Re: Airplane on a treadmill question
InfX708 Offline
Member

Registered: 24/09/00
Posts: 864
Loc: Ft. Bragg, NC
Ok, I'm working with Iraqis and have now become a master of trying to explain things in tiny detail - also works for U.S. Army staff officers who have never left the wire. Here are the conditions we are operating under: An airplane traveling at say 300mph, thrust being provided by its engines. A tread mill under the bird is traveling at 300mph in the opposite direction (this is drag). Since thrust must be more than drag, by an amount that differs from bird to bird, this particular aircraft won't fly until more thrust is provided, assuming there is no head, tail, or side wind. The treadmill is essentially pushing the aircraft backward while the engines push forward. Everyone knows there are 4 forces working on an airplane, right? Thrust must exceed drag by a certain amount to generate lift, which is caused by air flowing over the wings. There are a number of physical laws, principles, and effects involved and you can read here if you are interested. Suffice to say that the wing has to be moving relative to a fixed point on the ground, in the absence of any air movement, in order to fly. So, if the thrust does not overcome the rearward speed of the treadmill, it matters not the length of the treadmill. The aircraft won't fly until it generates enough thrust to move the wings through the air. Bottom line, on a calm day, you can not stand next to the tread mill, facing the side of the fuselage and watch the plane take off without moving any part of your body relative to the earth.
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#607424 - 08/11/07 08:39 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


Leave it to the Army of One to fuck that up!

Your premise that the conveyor traveling at 300 MPH in the opposite direction having equal affect as the thrust is false. 300 MPH conveyor has very little drag at all therefore thrust > drag.

USMC > ARMY

[Finger]

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#607425 - 08/11/07 10:09 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


To clarify, the landing gear has the effect of minimizing friction with the conveyor/treadmill. The effect of the treadmill is negligible.

Remember, the thrust of the aircraft works against air. The conveyor only spins the wheels.

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#607426 - 08/11/07 10:15 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


If the plane is on a treadmill where is the air coming from to lift the plane?

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#607427 - 08/11/07 10:40 PM Re: Airplane on a treadmill question
Anonymous
Unregistered


Quote:
Originally posted by chumpmann:
If the plane is on a treadmill where is the air coming from to lift the plane?
The engines are providing the thrust. The wheels are there to reduce friction but we already covered this...

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#607428 - 09/11/07 02:04 AM Re: Airplane on a treadmill question
InfX708 Offline
Member

Registered: 24/09/00
Posts: 864
Loc: Ft. Bragg, NC
Quote:
Originally posted by Timmah:
Leave it to the Army of One to fuck that up!

Your premise that the conveyor traveling at 300 MPH in the opposite direction having equal affect as the thrust is false. 300 MPH conveyor has very little drag at all therefore thrust > drag.

USMC > ARMY

[Finger]
Leave it to a jar head not to comprehend simple analogies. Draw out a diagram showing the forces acting on an airplane. The one that pushes from the front is called drag. Therefore, anything pushing back against the aircraft's forward movement is drag, i.e. a conveyor belt moving 300 mph. It sure as hell isn't gravity, lift or thrust. If there was no thrust from the engines, the aircraft would move backwards at 300mph. The aircraft would not just sit there in one spot, unless you had frictionless wheels. If that's the case, then the treadmill is pointless anyway - it's not exerting any sort of force on the airframe. In order for an airplane to take off, thrust must overcome drag by a given amount. This generates lift which overcomes gravity. Next you're going to tell me that if I can an ostrich on a treadmill going fast enough, it will fly. But it's easy to just make statements with any explanation to back it up - just like a jar head.
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300,000 miles, and counting

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#607429 - 09/11/07 02:15 AM Re: Airplane on a treadmill question
InfX708 Offline
Member

Registered: 24/09/00
Posts: 864
Loc: Ft. Bragg, NC
Quote:
Originally posted by Timmah:
Quote:
Originally posted by chumpmann:
[b]If the plane is on a treadmill where is the air coming from to lift the plane?
The engines are providing the thrust. The wheels are there to reduce friction but we already covered this...[/b]
You still didn't explain where the air moving over the wings to provide lift comes from. The engines simply hold the plane in place on the treadmill, assuming the plane is not moving forward relative to a ground observer. Engines provide thrust which is forward movement. We've already established in our model that the plane is not moving forward to a fixed observer - i.e. someone not on the treadmill.

To look at it from a different angle, if you put an airplane on a fixed runway with the highest friction wheels available and put a huge fan in front capable of moving the air over the wings at take off speed, the airplane would take off. It would have zero forward movement relative to the ground observer, but it would have sufficient air flowing over the wings to generate lift. Thrust does not provide lift. Thrust provides forward movement through the air.
_________________________
300,000 miles, and counting

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#607430 - 09/11/07 02:59 AM Re: Airplane on a treadmill question
Anonymous
Unregistered


I did explain it. The plane rolls because if the treadmill moves 300 MPH in the opposite direction it isn't enough drag to stop the plane from taking off.

Thrust > Drag = plane moves and flies.

I'll drag up this example...

OK lets say you're on roller skates and standing on a moving sidewalk. I'm not on the sidewalk. I hand you a tow rope and walk the opposite direction of the sidewalk. Do you move? yes

Let's say we quadruple the speed of the sidewalk and I still walk in the opposite direction. Do you still move? Yes

How much drag does the moving sidewalk affect me? The answer is very little.

The plane's engines overcome the minimal amount of drag the conveyor offers and the plane takes off.

The only way the conveyor stops the plane is if it can produce enough speed which in turn will produce enough drag to counter the engine's thrust. It however isn't matching the planes speed at that point but greatly exceeding it. It isn't going 50 MPH in the opposite direction. I would have to go much faster than that to stop a plane that needs to get up to 50 MPH to take off.

That simple enough?

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#607431 - 09/11/07 03:37 AM Re: Airplane on a treadmill question
InfX708 Offline
Member

Registered: 24/09/00
Posts: 864
Loc: Ft. Bragg, NC
Quote:
Originally posted by Timmah:
I did explain it. The plane rolls because if the treadmill moves 300 MPH in the opposite direction it isn't enough drag to stop the plane from taking off.

Thrust > Drag = plane moves and flies.

I'll drag up this example...

OK lets say you're on roller skates and standing on a moving sidewalk. I'm not on the sidewalk. I hand you a tow rope and walk the opposite direction of the sidewalk. Do you move? yes

Let's say we quadruple the speed of the sidewalk and I still walk in the opposite direction. Do you still move? Yes

How much drag does the moving sidewalk affect me? The answer is very little.

The plane's engines overcome the minimal amount of drag the conveyor offers and the plane takes off.
Ah, but you moved. That totally eliminates the original question. Now, if you are the observer, then I don't move forward relative to you, since you and I are moving forward at the same speed. Relative to the sidewalk, I am moving forward faster than it is moving backward and will continue to do so as long as you are pulling me forward, but my position relative to you will not change. Thus, to you, I will appear to not be moving at all.
Now, if you modify the original question and throw in the detail that the aircraft moves forward relative to the ground observer, then yes, the aircraft will lift off once it has achieved enough forward airspeed. After all, it is all about airspeed. Ground speed is irrelevant. Right now, we are all moving at about 1300 ft/sec relative to the sun, but since the air around us is moving at the same speed, on a calm day, we have zero air speed.

For clarity, this whole thing is dependent upon relativity. Assumptions are that the airplane is moving 300mpg forward relative to the conveyor. The conveyor is moving 300mph backward relative to the ground observer. Therefore the aircraft is moving at 0 mph relative to the ground observer. Now, if the plane is moving forward 300mph relative to the ground observer, who is stationary relative to the Earth and the surrounding air, then yes, the plane will take off, assuming that it takes off at 300mph. but, if the plan is moving forward at 300 mph relative to the ground observer and the treadmill is moving backward 300mph relative to the ground observer, then the plan is moving forward 600mph relative to the runway (conveyor belt). So in reality, it's a flawed question and your answer depends on your point of view, literally.
_________________________
300,000 miles, and counting

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#607432 - 09/11/07 03:40 AM Re: Airplane on a treadmill question
Anonymous
Unregistered


I think that is the point. Yes I moved. Yes the plane moves because the drag is less than thrust.

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#607433 - 09/11/07 03:48 AM Re: Airplane on a treadmill question
InfX708 Offline
Member

Registered: 24/09/00
Posts: 864
Loc: Ft. Bragg, NC
Ok, at that point, the plane speed forward is greater than the conveyor's speed backward, resulting in a forward movement overall, thus existing outside the parameters of the question. Like I said, it all depends on the point of observation and relativity.
_________________________
300,000 miles, and counting

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#607434 - 09/11/07 04:19 AM Re: Airplane on a treadmill question
Mobycat Offline
Member
*****

Registered: 12/09/00
Posts: 8374
Loc: the hue of dungeons and the sc...
Quote:
Originally posted by InfX708:
Like I said, it all depends on the point of observation and relativity.
And the fact that the question is worded badly.

Pretend there is *zero* friction, and the engines are off - if the conveyor belt moves in ANY direction, the plane is going to stand still. Isn't that the law of inertia?

Key here - ZERO friction - there is no external force to push the plane back if there is ZERO friction.
_________________________
"Nature has constituted utility to man the standard and test of virtue. Men living in different countries, under different circumstances, different habits and regimens, may have different utilities; the same act, therefore, may be useful and consequently virtuous in one country which is injurious and vicious in another differently circumstanced" - Thomas Jefferson, moral relativist

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