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Re: Mass re: E=mc^2



I lost my ability to send emails for about a week. After extensive work on
my computer, this is a good test to see if I'm able to talk to the outside
world.

-----Original Message-----
From: Forum for Physics Educators [mailto:PHYS-L@list1.ucc.nau.edu] On
Behalf Of Michael Edmiston

I usually answer that question by saying matter is "bound energy" or by
saying it is "localized energy."

I suppose that will bring the question "what is energy." The only
response I have to that is... energy is what the universe is made of.
------------------

I have a problem with envisioning the world as made of "energy". We have
recently discussed the Work-Kinetic Energy theorem. This is a way of
transforming the vector equation F=ma into a scalar form that is easier to
work with - the result being the invention of a quantity 1/2 mv^2. I find it
hard to imagine a universe made up of an invented scalar quantity whose
original purpose is simply a bookkeeping tally of the product of
acceleration and distance. I certainly couldn't think of a convincing way to
discuss this approach with an introductory physics student.

I am, however, more comfortable of the idea of mass as coming from the
forces of interaction at the submicroscopic level and being quantified by
the potential energies associated with these interactions (i.e. "tensions"
in space)

Bob at PC