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The change in momentum of the gas after it leaves the rocket cannot, at leasst in first order, have any effect on the rocket. I don't understand your remark after the "but".
Regards,
Jack
On Mon, 24 Jul 2006, Marc "Zeke" Kossover wrote:
--- Jack Uretsky <jlu@hep.anl.gov> wrote:
The answer toThis is what I originally thought (and the student, too)
what is getting
upward momentum is, simply, the earth. The added
downward momentum from
the gas is from the gravitational attraction of the
each.
but it leaves out the fact that the rocket does get some
positive momentum as well. The rocket end up upwards from
it's original position, even though it remains the same
distance from the planet.
I advocate keeping it simple and accompanying theSure, but he was wondering about momentum conservation. And
answer with a
diagram showing the gas, the earth, the mutual forces
acting on each, and
nothing else.
I think that he was leading me towards asking the more
vexing question about momentum conservation in a plane with
level flight.
Marc "Zeke" Kossover
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