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Re: What is weight?




Well, John, that *is* complicated. Now that you've defined
it, how do you *measure* it? Albert Einstein says you can't.
I think he's right.

Leigh

But surely pedagogically we are not going to discuss General Relativity
in a high school or beginning college class. We are talking about
acquiring some workable understanding of basic Newtonian Mechanics.
As such, there are preferred frames, so called intertial frames, where
the meaning is perfectly well defined and measurable.

I point out that in even in GR, the gravitational field is transformable
away only at a point. As soon as one considers an extended region, real
gravitational fields are NEVER equivalent to an accelerated frame since
real fields are never uniform.

J. EPstein

I don't propose to discuss GR in class; I do (and if you look at my
transparencies you will see that I did) discuss briefly the principle
of equivalence. I don't really get your quibble about gravitational
fields being nonuniform. When I define weight I do so locally, and my
(vector) g is uniform throughout the hypothetical laboratory in which
my model systems are set. I can certainly hypothesize a uniform
gravitational field; what you mean by "real" fields is obscure.

Leigh