-----Original Message-----
From: Ludwik Kowalski <kowalskiL@Mail.Montclair.edu>
Would you agree that
"the concept of work has no meaning unless a working force is
specified"?
Not necessarily. The work-energy theorem deals with the Net Work done on an
object. That NET Work can be calculated as the algebraic sum of the
individual works where one considers the work done by each individual force
OR it can be the work done by the NET force acting on the object. The
problem for students (and for us) is that work can be both positive and
negative and thus the NET work can sum to zero even when there IS work being
done on an object by individual forces. The only real objection to
Ludwick's statement would be that the principle is useful 'the other way
around'. That is, if we recognize that the KE of an object is not changing
then the Net Work must be zero. If we can clearly identify one agent as
doing work on the object, then we are forced to find another agent(s) also
doing work (+/-) such that the total work is zero. Hence the work concept
can be used to help find the forces. Maybe this is the same as 'specifying'
the forces, but I see it as a slightly different approach.