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Re:




Bill Adlam wrote:

> Work is the amount of energy changed from one form to another (i.e.
> expended).  It doesn't have a direction.  When an object moves, work
> is equal to force times distance.
>
> Bill

Almost, but not quite.  When a force is applied to a solid object
constrained so that it can move only in a plane oriented perpendicular
to the force, then the force exerts no work on the object.  In other
words, a 50 pound vertical force acting on an object which moves 10 feet
horizontally across a frictionless plane, results in zero work rather
than 50 foot-pounds of work.  Needless to say, this description implies
that the horizontal motion is not a consequence of the vertical force.

Of course, work can be described in more than one way.  For example, one
of the ways 'flow work' can be done on a fluid system is when the
pressure forces on the boundaries move, for example in a tapered
cylinder when p1A1 and p2A2 at the end sections move through delta S1
and delta S2 respectively.  We could go on with different scenarios at
length, but again I think we are moving away from dinosaurs.
Jim