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#1 |
Bioengineer and aspiring lawer
Join Date: Apr 2006
Location: Pittsburgh
Posts: 872
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We all have been assuming that the air does not accelerate with the treadmill, which is correct. It is also why the treadmill has no effect. The jet engines push against the AIR, nothing else, so if the air does not accelerate with the treatmill then there must be a constant force pushing back on the aircraft (basic physics). Since the treadmill is only in contact with the wheels, and the wheels cannot transmit a force back onto the aircraft (no brakes being applied), there is an unballenced force acting on the body of the plain. Therefore, the plane must accelerate.
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#2 | |
I think this line's mostly filler.
Join Date: Jan 2003
Location: DC
Posts: 13,575
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Quote:
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#3 | |
The future is unwritten
Join Date: Oct 2002
Posts: 71,105
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Jet engines don't push against the air, they push against the plane. The plane will be pushed forward until it reaches takeoff velocity, no matter what speed the wheels are turning. All they do is keep the plane from dragging on the ground. Planes take off from runways that are moving at 1000 mph, under them, every day.
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The descent of man ~ Nixon, Friedman, Reagan, Trump. |
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#4 |
still says videotape
Join Date: Feb 2001
Posts: 26,813
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9 pages on topic, impressive. Unless the runway is moving air, you've got nothing but a over-powered paper weight.
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#5 |
Bioengineer and aspiring lawer
Join Date: Apr 2006
Location: Pittsburgh
Posts: 872
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and it keeps the covers from falling down into the sewers
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#6 | |
The future is unwritten
Join Date: Oct 2002
Posts: 71,105
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The descent of man ~ Nixon, Friedman, Reagan, Trump. |
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#7 |
Not Suspicious, Merely Canadian
Join Date: Oct 2006
Posts: 3,774
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I changed my mind. Bruce is right; the jet engines aren't pulling air over and under the wings; in fact, the engine doesn't even have to be on the wing. The engines are pushing the plane to achieve atmospheric air flow over and under the wings. Since the treadmill plane isn't moving relative to the atmosphere, the needed air flow around the wings doesn't happen and there's no lift; just a lot of engine revving and wheel-spinning. It doesn't matter what 'ground speed' the instruments record, the plane has no velocity relative to the air around it. The thing won't fly, any more than a kite will fly if you hold its string while running on a treadmill.
That's my story, and I'm stickin' to it. :p
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#8 | |
The future is unwritten
Join Date: Oct 2002
Posts: 71,105
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#9 | |
Not Suspicious, Merely Canadian
Join Date: Oct 2006
Posts: 3,774
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If you run on a treadmill, does air flow past your face (assuming no fan!)?
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#10 |
The future is unwritten
Join Date: Oct 2002
Posts: 71,105
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The plane isn't running on a treadmill, that's not how it moves. It moves by pushing through the air...the treadmill has no bearing on the plane.
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The descent of man ~ Nixon, Friedman, Reagan, Trump. |
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#11 |
We have to go back, Kate!
Join Date: Apr 2004
Location: Yorkshire
Posts: 25,964
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*pokes head into room.....realises is totally out of depth and retreats*
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#12 |
Bioengineer and aspiring lawer
Join Date: Apr 2006
Location: Pittsburgh
Posts: 872
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But the engines still exert a force against the body of the aircraft, and since the runway can't exert any force in the absence of friction, their is a net acting force on the aircraft
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#13 |
still says videotape
Join Date: Feb 2001
Posts: 26,813
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but no lift
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If you would only recognize that life is hard, things would be so much easier for you. - Louis D. Brandeis |
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#14 | |
I'll just put the tip in
Join Date: Oct 2006
Location: NC
Posts: 39
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#15 | |
Snowflake
Join Date: Mar 2006
Location: Dystopia
Posts: 13,136
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#1: If the "forward speed" is defined as relative to the treadmill then the plane is stationary relative to the air. #2: If the "forward speed" is defined as relative to the ground, then it is possible for the plane to be in motion relative to the air. Nothing in the question rules out either of these interpretations, and no amount of blustery hoopla or physics masturbation can change that. The question is unanswerable as stated. It's designed that way on purpose.
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****************** There's a level of facility that everyone needs to accomplish, and from there it's a matter of deciding for yourself how important ultra-facility is to your expression. ... I found, like Joseph Campbell said, if you just follow whatever gives you a little joy or excitement or awe, then you're on the right track. . . . . . . . . . . . . . . . . . . . . . . . . . . Terry Bozzio Last edited by Flint; 12-07-2006 at 08:29 PM. |
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