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Can a Plane on a Treadmill Take Off?



 
 
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  #1  
Old February 8th 06, 08:08 PM posted to rec.aviation.student,rec.aviation.piloting
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Default Can a Plane on a Treadmill Take Off?

"alexy" wrote in message
news
Just to "set the hook" here, are you saying that it will be possible
to have the conveyer move backwards fast enough that the plane remains
still, even under full power, and with no brakes on?

I thought you had already established that it would be possible, and that
the treadmill speed is "somewhat below the speed of light"? You didn't
appear to solve the "materials integrity" aspect of the problem, but that
seems like a minor quibble.

Pete


  #2  
Old February 8th 06, 08:18 PM posted to rec.aviation.student,rec.aviation.piloting
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Default Can a Plane on a Treadmill Take Off?

"Peter Duniho" wrote:

"alexy" wrote in message
news
Just to "set the hook" here, are you saying that it will be possible
to have the conveyer move backwards fast enough that the plane remains
still, even under full power, and with no brakes on?


I thought you had already established that it would be possible, and that
the treadmill speed is "somewhat below the speed of light"? You didn't
appear to solve the "materials integrity" aspect of the problem, but that
seems like a minor quibble.


No fair; that's the next question, not to be asked out of order!! ;-)

--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.
  #3  
Old February 9th 06, 01:50 PM posted to rec.aviation.student,rec.aviation.piloting
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Default Can a Plane on a Treadmill Take Off?

"Peter Duniho" wrote:

"alexy" wrote in message
news
Just to "set the hook" here, are you saying that it will be possible
to have the conveyer move backwards fast enough that the plane remains
still, even under full power, and with no brakes on?


I thought you had already established that it would be possible, and that
the treadmill speed is "somewhat below the speed of light"? You didn't
appear to solve the "materials integrity" aspect of the problem, but that
seems like a minor quibble.

You know, there is a fallacy in my reasoning that I am surprised no
one has called me on. We are used to aerodynamic drag, which increases
as the square of velocity. But if my memory of high school physics is
correct (and if Newton hasn't changed his mind in the last 40
yearsg) the friction between two bodies is a coefficient of friction
times the force normal to the motion (i.e., the weight of the plane).
No component for the relative velocities of the two bodies! So the
drag due to wheels is small, and speeding up the conveyer will not
increase that small drag, at least until you get to the "noise"
elements that make the idealized drag model imperfect.

I guess that by _accelerating_ the conveyer, you could make the plane
use all of its power for a short while providing the angular
acceleration to the wheels, but you very quickly get to relativistic
speeds, without ever reaching a steady state tradeoff for the
engine/prop's thrust.

Much easier to just read the problem as stated, and have the conveyer
only move as fast backwards as the plane moves forward!!

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  #4  
Old February 9th 06, 06:29 PM posted to rec.aviation.student,rec.aviation.piloting
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Default Can a Plane on a Treadmill Take Off?

"alexy" wrote in message
...
You know, there is a fallacy in my reasoning that I am surprised no
one has called me on. We are used to aerodynamic drag, which increases
as the square of velocity. But if my memory of high school physics is
correct (and if Newton hasn't changed his mind in the last 40
yearsg) the friction between two bodies is a coefficient of friction
times the force normal to the motion (i.e., the weight of the plane).
No component for the relative velocities of the two bodies!


Hardly seemed worth it, given the opportunity to equivocate on the point.
In particular, while the idealized friction drag remains static relative to
speed, that ignores the possibility for change in the materials as the
friction heats them. Expansion may create a higher normal force (depending
on what part expands faster), and thus higher frictional drag. It also
ignores aerodynamic drag around the surface of the tire.

While I haven't bothered to calculate what these increases would be, it
seems safe to say that it's *possible* they would rise fast enough to offset
the available thrust before reaching the speed of light.

Basically, in an arm-chair, lay-person discussion like this, practically
*anything* is possible as you approach the speed of light. So why not just
invoke that, and ignore the details?

Pete


  #5  
Old February 9th 06, 07:29 PM posted to rec.aviation.student,rec.aviation.piloting
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Default Can a Plane on a Treadmill Take Off?

Strap a big enough engine on the treadmill, and one way or another,
you'll make it take off.



  #6  
Old February 9th 06, 08:03 PM posted to rec.aviation.student,rec.aviation.piloting
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Default Can a Plane on a Treadmill Take Off?

("Peter Duniho" wrote)
While I haven't bothered to calculate what these increases would be, it
seems safe to say that it's *possible* they would rise fast enough to
offset the available thrust before reaching the speed of light.

Basically, in an arm-chair, lay-person discussion like this, practically
*anything* is possible as you approach the speed of light. So why not
just invoke that, and ignore the details?



Let's take this away from the light...

For the plane NOT to take off - the plane must have zero forward
movement/airspeed. According to the OP rules, in that state the belt is
stationary.

If the prop is pulling at the plane to go forward, the belt can keep up
(debate-debate-debate) causing the plane not to make any headway. Again,
in-that-state, the belt must (now) stop because it only travels backward at
the same speed as the plane moves forward - but the plane is still pulling
forward ...against a (now) stationary belt.

I'm (now) officially confused.


Montblack
http://www.artfinale.com/store/sku_pgs/E06BT.php
Taking steps to get the right answer.

  #7  
Old February 9th 06, 08:36 PM posted to rec.aviation.student,rec.aviation.piloting
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Default Can a Plane on a Treadmill Take Off?

Help, we're all on a treadmill and we can't get off.

What can we take for brain misfunction?

  #8  
Old February 9th 06, 11:03 PM posted to rec.aviation.student,rec.aviation.piloting
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Default Can a Plane on a Treadmill Take Off?

"Montblack" wrote in message
...
Let's take this away from the light...

For the plane NOT to take off - the plane must have zero forward
movement/airspeed. According to the OP rules, in that state the belt is
stationary. [...]


See, this is where you went wrong. This little tangent is not about the
original post's rules. The original problem has been modified for the
purpose of entertainment, not enlightenment.


 




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