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Re: Center-of-mass system



"Center of momentum" is to be preferred in general because it admits
relativistic particles to the system. "Center of mass" is certainly
the better way to introduce the concept in an introductory course.

Of greatest importance is that one should *never* allow the use of
"center of gravity"! There is no case where this atrocious construct
is more appropriate than "center of mass".

Leigh

I hadn't thought about the effects of relativity on the center of
mass when I replied to this thread a few minutes ago. I'm going to
have to think about that some more. But I don't see anything so
egregious about center of gravity, as long as we remember that cg and
cm are the same only when the gravitational field is uniform, so, to
the extent that we can take the Earth's grav. field to be uniform
near the surface, the cg and cm are interchangeable terms. Having
said that, I agree that center of mass is by far the preferable term,
and we use it at all times in my classes, just as soon as we have
made clear the difference between the two.

Hugh
--

Hugh Haskell
<mailto://hhaskell@mindspring.com>

Let's face it. People use a Mac because they want to, Windows because they
have to..
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