Re: Double Your Momentum, Reflection


Charles wrote:
>On 7 Dec 2005 12:26:24 -0800, "PD" <TheDraperFamily@xxxxxxxxx> wrote:

>>Initially, ball has momentum +P and wall has momentum 0.
>>Finally, ball has momentum -P and wall has momentum +2P.
>>Total momentum is conserved (+P in both cases).

>I managed to confuse myself with your explanation.

>Imagine two walls. Let's put them in orbit, so there is no coupling
>between them. Elastic ball and walls. so little loss.

>the ball hits one wall and results in the momentum as you state. It
>bounces to the second wall, regains its +p momentum and imparts -2P
>momentum to the second wall. Then it bounces to the first wall again,
>which still has its +2P momentum, now it gets 2 more, so it results in
>+4P? This can progress for a long time?

Yes, in principle it can keep going until the walls are moving outward,
each with half of the kinetic energy the ball originally had. As the
walls move apart faster and faster, the ball loses more and more
velocity with each bounce.

Isaac Kuo

.

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