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Re: Rocket action



On Thu, 9 Dec 1999, brian whatcott wrote:

At 15:53 12/9/99 -0500, Robert Cohen wrote:
On Fri, 3 Dec 1999, brian whatcott wrote:

At 08:52 12/2/99 -0500, Rick Tarara wrote:

It is easy to 'see' that the rocket can continue to accelerate under a
sustained thrust, but less obvious how the center of mass (rocket starting
in space, originally at rest) remains fixed and at rest, especially
once the
speed of the rocket exceeds the speed of the exhaust. ;-)
///
Richard W. Tarara

I believe Rick would want to reconsider this mind experiment.

brian whatcott <inet@intellisys.net>
Altus OK


Why reconsider it? Is something wrong with it?


I have written up my objection to the list two or three
times by now. Is the objection not intelligible?

The idea of a time progression until a rocket outraces its
exhaust is a physics textbook fairy tale in essence, if you
consider that its exhaust can be throttled to low velocity
at some indefinitely early stage.

I'm sorry but you've lost me. What is it, specifically, about Rick's mind
experiment that you object to? Is it his statement that the center of
mass remains fixed? It seems reasonable to me and I'd like a clear
explanation for why it is wrong. By the way, I've only been a member of
this list for a short while and so I may have missed your earlier posts
(although I checked the archive and couldn't come up with anything).

----------------------------------------------------------
| Robert Cohen Department of Physics |
| East Stroudsburg University |
| bbq@esu.edu East Stroudsburg, PA 18301 |
| http://www.esu.edu/~bbq/ (570) 422-3428 |
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