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- Newsgroups: sci.physics
- Subject: Re: Converting the masses
- Message-ID: <mcirvin.711903684@husc8>
- From: mcirvin@husc8.harvard.edu (Mcirvin)
- Date: 23 Jul 92 15:01:24 GMT
- References: <n0596t@ofa123.fidonet.org> <mcirvin.711489157@husc10><9868@sun13.scri.fsu.edu
- > <1992Jul22.193837.18095@sfu.ca> <MATT.92Jul22142345@physics.berkeley.edu>
- Nntp-Posting-Host: husc8.harvard.edu
- Lines: 33
-
- matt@physics.berkeley.edu (Matt Austern) writes:
-
- >In article <1992Jul22.193837.18095@sfu.ca> palmer@sfu.ca (Leigh Palmer) writes:
-
- >> "Mass" as you use it
- >> is equal to neither inertial nor gravitational mass as those terms apply to
- >> any system more complicated than a particle at rest!
-
- >There is, however, *nothing* which is equal to either inertial or
- >gravitational mass for a relativistic body.
-
- >That is: I define the inertial mass of a body as the "m" appearing in
- >the equation
- > F = m a, (1)
- [...]
- >I believe that these definitions are customary; I don't know what
- >other meaning could be attached to the phrases "inertial mass" or
- >"gravitational mass."
-
- Wellll, if you define F as dp/dt instead, and then define inertial
- mass by the formula p = mv, then the total energy
- (or "relativistic mass") *does* become exactly the "inertial mass."
- But I still don't think this should be used in physics classes.
-
- As for gravitational mass, I agree with you there: there really
- isn't any such thing in the context of GR, unless you want to
- define it trivially as the "inertial mass" defined above because
- acceleration is independent of mass-- but that's hardly the
- best way to look at it, though it's the language that often
- gets used.
-
- --
- Matt McIrvin mcirvin@husc.harvard.edu Long live short .sigs
-