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Robert Cohen wonders as follows:energies
Is energy conserved (i.e., energy that does not include "pretend"
bylike PE)?
Integrate N#2 --> Int F*ds = Int ma ds
We _define_ Int F*ds as work and Int ma ds = 0.5mv^2 as KE == energy --
definition.This
Some of this work we call PE and we lump the PE and the KE together --
is not always helpful in an intro class.for a
Now N#3 says that the F on the system in question = -F on the applicator
Thus the work done on the system = - the work done on the applicator.
And it then follows that energy increase of the system = the decrease of
the energy of the applicator. Total KE is conserved -- always -- even
complicated interaction with multiple particles.***************************************************
your
But KE + PE is _not_ always conserved.
Now some on this list will want to use "enhanced" language but this is
quite adequate for an intro class -- and beyond.
But if you try to say that energy flows, you do a great disservice to
students.time
Surely we all know all of the above; we just need to be reminded from
to time how simple this is.
Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen