Re: [Phys-l] teaching energy

["R. McDermott" <rmcder@gmail.com>]

----- Original Message ----- 
From: "Rauber, Joel" <Joel.Rauber@SDSTATE.EDU>
To: <phys-l@carnot.physics.buffalo.edu>
Sent: Thursday, September 28, 2006 3:51 PM
Subject: Re: [Phys-l] teaching energy


> I just made a quick (5 minute) cursory glance at the reference below; it
> appears very interesting, however, I'm bothered a bit by the discussion
> of gravitational PE on page 3.
>
> |
> | Please read "Making Work Work" at
> | <http://modeling.asu.edu/modeling/MakingWorkWork.pdf
> <http://modeling.asu.edu/modeling/MakingWorkWork.pdf> >
>
> The author makes much of saying saying that we won't say there is a PE
> associated with the system of two masses, since we can't locate the
> energy in either body. Therefore they conclude that it resides in the
> gravitational field.
>
> I fail to see what is wrong with associating PE with the system, the
> distance between the objects being the state variable. They mention this
> interpretation and then reject it.

The central theme is that the energy must reside somewhere.  Taken in that 
context, the only "place" for it to be is in the field itself.

> I suppose they must do the same thing when it comes to discussing PE of
> a system of 2 charges. I.e. the modelers calculate energy in a charge
> configuration by integrating E^2 over a volume, rather than by
> qQ/distance???

Not necessary.  The calculation of energy proceeds as usual, it is simply a 
case of where that energy "resides".