Re: Rocket action

[Richard Tarara <rtarara@SAINTMARYS.EDU>]

----- Original Message -----

> On Wed, 1 Dec 1999, Greg Kifer wrote:
>
> > I remember, but don't know from where, hearing that a rocket can go no
> > faster forward than the exhaust gases leave the exhaust nozzle.  Is this
> > correct?  If so, can someone explain the whys and wherefores to a simple
> > high school teacher like me.  Thanks in advance.
>
> On the contrary, it's easy to make a rocket "go faster" than its exhaust.
> All *you* have to do is outrace its exhaust in the other direction.
>
> Notice that, by Newton's first law, it takes absolutely no effort for you
> to continue to do this and, if the rocket continues to produce *any*
> thrust whatsoever, it will go *even* faster!

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.  ;-)

Rick

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