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Re: CONSERVATION OF ENERGY



On Mon, 21 Jul 97 16:37:30 Al Bachman <BACHMAN@rfmh.org> wrote:


With respect to the original problem situation: there appears to be a
basic confusion about the identity of the SYSTEM.

True. Can you, please, edit the problem in a more appropriate way and
poste it? After all the situation is worth discussing. Compairing what our
"ideal" students would be expected to write on the hypotetical exam is a
good way of keeping things simple.

If [the system] includes the two iron components, then the Work done ON
the system is zero. If the system as described is isolated then dQ is also
zero, and the total energy internal to the system is constant.

Yes indeed. But the use of the boundary idea was up to a student who might
be expected to reply exactly as above. And why is it necessary to define
the boundary in order to predict by how much will the temperature rise
after the system is equilibrated?

I am troubled by application of the term 'Internal Energy' and its
confusion with situations in which ...

I am working on terminology with which we may perhaps all agree. Will
post it separately today.
Ludwik Kowalski
P.S.
The question 'how is thermal energy (injected into the system) distributed
between the two pieces of iron' was not on the exam. But it can be added.
My ideal student would answer: 'in proportion to masses, after the
equilibrium is established'.