Re: wave momentum

["James W. Wheeler" <jwheeler@EAGLE.LHUP.EDU>]

To drive a microphone-e.g. a variable capacitor type, it must exert a
force, hence it must carry momentum!  The average momentum over a cycle
may well average to zero-but it is not zero at every point in the cycle.

On Fri, 12 Mar 1999, James McLean wrote:

> "James W. Wheeler" wrote:
> > But the Maxwell tape ad is about a longitudinal wave that carries enough
> > momentum to drive (e.g.) a pick up microphone.
> It carries enough *energy* to drive a microphone.  I don't think there
> is a net change in the velocity of the microphone (and hence in it's
> momentum).  First increased pressure pushes it one way, then decreased
> pressure pulls it the other.
>
> --
> --James McLean
> jmclean@chem.ucsd.edu
> post doc
> UC San Diego, Chemistry