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From: guy@rlgvax.UUCP (Guy Harris)
Newsgroups: net.physics
Subject: Re: eV Revisited
Message-ID: <1686@rlgvax.UUCP>
Date: Wed, 8-Feb-84 22:51:42 EST
Article-I.D.: rlgvax.1686
Posted: Wed Feb  8 22:51:42 1984
Date-Received: Fri, 10-Feb-84 03:34:52 EST
References: <1559@pur-ee.UUCP>
Organization: CCI Office Systems Group, Reston, VA
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>   Mass and energy are related to each other by a constant.  This
> constant is c^2.  If you know something's mass and want the energy
> associated with that mass, you use the well known equation E=mc^2.
> Likewise, to obtain mass from energy, divide the energy by c^2.
> The point of the whole thing is this.  You cannot specify mass
> by using units of energy.  You have to use units of mass, and the
> unit of mass associated with eV is eV/c^2.   Not simply eV.

However, given that c^2 is a constant, you can specify mass by giving
the energy equivalent of that mass; saying that the electron has a mass
of .511 MeV is more convenient than saying it has a mass of .511 MeV/c^2,
so the e-/e+ mass is conventionally given as .511 MeV.

	Guy Harris
	{seismo,ihnp4,allegra}!rlgvax!guy