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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.
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.