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From: js2j@mhuxt.UUCP (sonntag)
Newsgroups: net.physics
Subject: Re: Potential Energy (could someone expand on the 'yes' answer?)
Message-ID: <1235@mhuxt.UUCP>
Date: Mon, 4-Nov-85 13:04:22 EST
Article-I.D.: mhuxt.1235
Posted: Mon Nov  4 13:04:22 1985
Date-Received: Tue, 5-Nov-85 23:11:53 EST
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Organization: AT&T Bell Laboratories, Murray Hill
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> >Is this true?  Does the potential energy stored in a spring
> >contribute to its rest mass?  How about a battery, a capacitor, etc?
> >->	    Jim Galbiati,  GenRad Inc,  Production Test Division	    <-
> 
> Yes.

     Wow, what an informative answer!  
     Lets consider a very simple system as a specific example.  Suppose we
have two electrons rather close together and very far from any other influence
at T=0.  They have some potential energy stored by virtue of their mutual
repulsion.  If we let them go, that potential energy is gradually converted 
to kinetic energy as they speed apart.  
     If we could measure the mass of these electrons, would we find that
the two-electron system has more than two electron rest masses?  Would we
find that each electron has more than one electron rest mass?  If we were
measuring the electron masses from the reference frame stationary w.r.t. the
electrons at T=0, would the extra mass measured as T => infinity be the
same as the extra mass measured due to relativistic effects, or would we
have to treat that apparent mass change seperately?
-- 
Jeff Sonntag
ihnp4!mhuxt!js2j
    "What would Captain Kirk say?"