Oops. My last message was intended to be for the AP physics list,
where I thought I was when I sent it. I haven't been talking about
the c of m approach here, but on the AP list. So those I confused by
my e-mail can just trash it without loss of content.
If anyone would like to hear more about the c of m method that I and
a few colloeagues have been using effectively for several years,
contact me off-list, and I'[ll be happy to explain it.