Re: Energy density; the correct one

[Robert Cohen <Robert.Cohen@PO-BOX.ESU.EDU>]

I wrote:
> > Situation 1. Suppose I hold two equally positively-charged
> particles, q1 and
> > q2, a distance r12 apart.  If I keep hold of q1 and release
> q2, q2 flies off
> > to a place infinitely far away and gains kinetic energy
> equal to E2. I then
> > release q1, which stays put since q2 is now infinitely far
> away.  The total
> > energy of the system is E2.
> >
> > [snip]
> >
> > In situation 1, I did no work on either q1 or q2.

to which David Rutherford [mailto:drutherford@SOFTCOM.NET] asked:

> Then how did they come to be r12 apart? If you did no work on
> them, then
> somebody (or something) else must have. If they are just sitting there
> without you holding them in position, then they will go
> nowhere when you
> "release" them.

I was not speaking of the work done by me to bring them together but rather
the work done on the particles as they separate.  I apologize for not being
more clear.

If the two are equal, so be it.  However, first answer the question I
propose, i.e.,
is the work done on the particles in situation 1 equal to the work done on
the particles
in situation 2?

____________________________________________
Robert Cohen; rcohen@po-box.esu.edu; 570-422-3428; http://www.esu.edu/~bbq
Physics, East Stroudsburg Univ., E. Stroudsburg, PA 18301