Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: CONSERVATION OF ENERGY




On Wed, 30 Jul 1997 09:26:22 -0400 (EDT) "W. Barlow Newbolt"
<wnewbolt@liberty.uc.wlu.edu> writes:
On Tue, 29 Jul 1997, Jim Green wrote:

At 05:57 AM 7/29/97 -0400, Gene wrote:
I would like to get a few things straightened out concerning
internal
energy--like what is it.

I am thinking that this question is too narrow -- It is a good
question of
course for spending time on phys-l ranting about words, but, to have
a
meaningful discussion, first you should say what the system is and
what
formalism you are going to use the concept in and for what purpose.


If you are going to use the First Law, you will also want to ask
what "Q"
and "W" are. And then if you want to include any more than "random"
motion,
you will need a good reason to do so. It can be done (and Leigh will
want
to), but the *usefulness* for doing so escapes me.

IE there is not much point in specifying "internal energy" in some
intergalactic formal sense for all time and space unless the rest of
the
problem is illuminated.




Jim Green
JMGreen@sisna.com





Jim,
The rest of the situation is illuminated! Consider the case
which has already been mentioned in this thread. A heavy cylinder is
filled with a mixture of gasoline and air sealed and insulated. In
the
side is a spark plug to which we can apply a spark whose energy
contribution may be considered negligible. The temperature goes up
when
the plug sparks; the pressure increases; but no heat is transfered, no

work is done, and there is no change in internal energy. In order to
understand how this can be we have to include all of the energy in the

internal energy.



W. Barlow Newbolt 540-463-8881 (telephone)
218 Howe Hall 540-463-8884 (fax)
Washington and Lee University newbolt.w@fs.science.wlu.edu
Lexington, Virginia 24450 wnewbolt@liberty.uc.wlu.edu

I think physics teachers should subtract at least one third from the
score for a problem that is solved without specifyinf formally what the
control volume or system is.

"What can you say about a society which insists that
God is dead, but which also insists that Elvis Presley
is alive?"
Irv Cupsinet

Why do you put this here? I would like to be presented with at least one
specimen of our society that insists both. Otherwise it's not funny.
The humor must come from a contradiction, but we already know that
different people think different things. Incidentally, I have never
encountered a person who claimed that a formerly living god is deceased.
That was way before my time unless I am very much mistaken - and I'm 63.
Did you see my polemic that slipped off the ends of my fingers last
night?
What did you think? I know. I am crazy.

Best regards / The Amateur