Re: Kinds of Mass

[DEVARAKONDA VENKATA NARAYANA SARMA <narayana@HD1.DOT.NET.IN>]

If we do not metion their different conceptual origins and then mention
their equivalence, an intelligent student may rediscover that they have
different origins and form a poor opinion of the critical thinking faculty
of the teacher and physics itself.

regards,

sarma.
At 06:31 PM 11/13/99 -0600, you wrote:
> Hi all-
>        In response to Rick Tarara:
> ***************************************************************
> I guess I don't understand why we hold onto the dual nomenclature.  Yes the
> conceptual origins suggested there might be a difference, but it seems that
> the experiments are pretty convincing that inertial and gravitational mass
> are identical.  Why continue to speak of these separately?  Are they ever
> different?  For example, what is the gravitational interaction between two
> masses moving parallel to each other (relative velocities zero).  Would one
> use the rest masses or the relativistic masses in GMm/R^2 (realizing that
> true relativists would probably never use the Newtonian formulation) and
> does it matter in terms of the inertial/gravitational nomenclature?
>
> Rick
>
> *******************************************************
>        If it were true that all substances experienced the same force from
> some standard mass (the Eotvos experiment), then the equality of
gravitational
> and inertial mass would be a matter of definition.  We would be free to
choose
> units for which equivalence it true (see Weinberg's book on gravitation where
> he discusses the "weak" equivalence principle).
>        The difficulty is that the Eotvos experiment, as is true of any
experiment,
> only establishes substance independence of gravitational force within a
range of
> uncertainty.  It is possible in principle, then, that some future
experiment will
> find a small, but non-zero difference, between, say, the gravitational
accelerations
> of a K-meson and a proton in the gravity field of the earth.  We would
then have
> to drop the "strong principle of equivalence" and distinguish between the
> gravitational and inertial masses of some substances.  There will be standard
> substances for which gravitational and inertial masses will be equal by
> definition.
>                                Regards,
>                                        Jack
>
>
>        "I scored the next great triumph for science myself,
> to wit, how the milk gets into the cow.  Both of us
> had marveled over that mystery a long time.  We had
> followed the cows around for years - that is, in the
> daytime - but had never caught them drinking fluid of
> that color."
>                Mark Twain, Extract from Eve's
>                Autobiography