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Re: [Phys-L] work versus mechanical transfer of energy



conserved? It may or may not be constant, but energy that enters or
leaves
the system can be accounted for.

enters or leave?

if you raise the system, the energy enters or leave the system?

the energy is in the system or in the earth or between both????

I think thermodynamics do not account for other kinds of energy (not
internal).

By adding energy to the system, I meant doing things that increase the
energy of the system. So things like heating, doing +work to the system, or
even adding particles. Any of these could change the energy total of the
system. The energy within the system would still be conserved (as always)
but would not have a constant value.

This internal energy would not be
constant, but it would be conserved.


?
My high school kids think that energy conservation only works for closed
and isolated systems (although they might not use those terms). They think
energy conservation (or any conservation principle) means the numerical
value is constant. So we work to see that energy can enter or leave a
system in a variety of ways. None of those ways violate conservation of
energy. So if a system consist of only a ball and earth, kicking the ball
is doing work to the system. It adds energy to the system changing the
numerical amount of energy, but does not violate conservation of energy.

I apologize for the initial lack of clarity.

John, I appreciate you modification. It was a subtle point. I didn't intend
to pick nits. I wanted to make sure I wasn't missing anything about U and
internal energies.

Have a good one.

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