Re: [Phys-L] defining energy

[Richard Tarara <rtarara@saintmarys.edu>]

Yes they are circular, and if not obvious to the kids, point that out, 
but energy is pretty abstract, really just a human construct.  The 
circularity is probably unavoidable at an operational definition level.  
I've always felt that concepts like mass, time, charge, and to a great 
extent energy are difficult if not impossible to really define in 
lower-level conceptual terms apart from operational definitions. It's 
like the Augustine statement on time--'if not asked, I know what it is, 
but if asked to explain (define) then I know I don't know. '

rwt

On 10/29/2013 2:13 PM, Philip Keller wrote:
> But if I define work as "the means by which energy is transferred",  then
> together my definitions are circular!  I am not looking to overwhelm my
> 11th graders with formality, but I would like the definitions to be
> logically sound.
>
>
>
>
> On Tue, Oct 29, 2013 at 1:49 PM, Richard Tarara <rtarara@saintmarys.edu>wrote:
>
> > If you just 'define' work as "the means by which energy is transferred
> > from one object to another and/or from one form to another" it is a little
> > cleaner.   Defining energy is still a problem--the 'ability to do work'
> > definition is pretty good for my world/national energy course, but
> > ultimately it boils down to a bookkeeping system for keeping track of
> > properties of nature that are conserved but moved and transformed by work.
> > The Feynman 'Dennis the Menace' story is useful at this level (and beyond),
> > and appears in Volume//one of the lectures but also in the Kirkpatrick and
> > Francis textbook.  I'm sure someone will provide an incomprehensible (to
> > 11th graders) more formal definition!  ;-)
> >
> > rwt


--
Richard Tarara
Professor of Physics
Saint Mary's College

free Physics educational software at
www.saintmarys.edu/~rtarara/software.html