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From: crl@pur-phy.UUCP (Charles LaBrec)
Newsgroups: net.physics
Subject: Re: eV Revisited
Message-ID: <1198@pur-phy.UUCP>
Date: Fri, 10-Feb-84 11:41:51 EST
Article-I.D.: pur-phy.1198
Posted: Fri Feb 10 11:41:51 1984
Date-Received: Wed, 15-Feb-84 04:28:41 EST
References: <1559@pur-ee.UUCP>
Organization: Purdue University Physics Dept.
Lines: 20

One of the first things you get used to in physics is differing unit
systems.  It is entirely possible (and in fact done) to devise a system
of units where the unit of mass = the unit of energy.  In relativity,
you often see c = 1, and perhaps time in units of distance.  In
quantum electrodynamics, a frequent practice is to define hbar, c, and
the mass of the electron = 1.  One of the things that irks me sometimes
is the variety of unit systems in electromagnetics.  There are the
MKS (SI), CGS(esu), CGS(emu), and Gaussian systems.

Looking at more common systems,  there are two English systems, one that
uses "pound-mass" and the other "slugs" to measure mass.  (I believe
something that weighs 1 lb.-force has a mass of 1 lb-mass in the former.)
Of course, a kilowatt-hr is a unit of energy (even though people commonly
say, "How much power did we use?").

So, the bottom line is, don't hold unit systems sacred.

Charles LaBrec
UUCP:		pur-ee!Physics:crl, purdue!Physics:crl
INTERNET:	crl @ pur-phy.UUCP