Re: ENERGY WITH Q

["Carl E. Mungan" <mungan@USNA.EDU>]

> What happens to mechanical energy when it gradually
> disappears? To answer this question one must be aware
> that frictional forces are always associated with increases
> of temperature.

Presumably you only mean KINETIC friction. Static friction does not
have this effect. eg. A box in the back of a pickup truck
accelerating without slipping.

>  Experiments performed by Count Rumford,
> and those performed by Joule, would be used to establish
> the mechanical equivalent of heat. Then I would say that
> caloric is not a substance, it is a form of energy.

Well, you said you didn't want to argue pedagogy, but you should at
least address the question of what you are going to tell your class:
ignore the textbook? Are you planning to rewrite the energy chapters
in whatever intro text you are using and give your class notes? I'm
unwilling to do that, but you may do as you wish.

I am here alluding to the following two points:

(i) Most texts don't introduce Q until the thermo chapter. I don't
see any good reason to introduce Q while the students are still
barely sorting out work and mechanical energy. Certainly I don't
think it helps solve problems in the mechanics section.

(ii) With apologies to some on this list, most texts don't refer to
heat as a *form* of energy. Instead it is a way to *transfer* energy
from one object to another. Mixing mechanisms for *changing* energy
of an object with the *kinds* of energy an object can have is a
recipe for confusion, IMHO.
--
Carl E. Mungan, Asst. Prof. of Physics  410-293-6680 (O) -3729 (F)
      U.S. Naval Academy, Stop 9C, Annapolis, MD 21402-5026
mungan@usna.edu    http://physics.usna.edu/physics/faculty/mungan/