Re: positive and negative work

["John S. Denker" <jsd@MONMOUTH.COM>]

On Sun, 11 Nov 2001, Joe Heafner wrote:
> Let's pick ONE SINGLE CORRECT defition and trash the rest.

I agree.  Excellent suggestion.

John Mallinckrodt wrote:

> >  "There is NO universally agreed upon definition of 'work.'"

I suppose that's true, but it's not useful.  The universe is a big
place;  there is no universal agreement on the definition of "green", or
anything else.  Still, many words have well-established conventional
meanings, which is what makes communication possible.

> Work (in any of its
> many forms) is conventionally *defined* as a product of some force
> with some distance (or, more generally, as a sum of integrals of
> infinitesimal such products.)

I would have said that work is conventionally defined to be the integral
of F dot ds, where ds is well-defined (and therefore work is
well-defined) if and !!only!! if we are dealing with pointlike particles
(i.e. no internal structure).

My colleagues know and understand this definition.  I expect students to
learn this definition.  I do not expect anyone to understand or even
remember any other definition.  Yes, I have read JM's papers, but I am
not persuaded by them.  There are innumerable idiosyncratic
generalizations of the notion of "work", but the assertion that they
worth learning is unproven and implausible.  They are are an impediment
(not an aid) to communication.

Recommendation:  When in doubt, decompose the system into pointlike
elements and apply F dot ds to each element separately.  If you do
anything else, you're strictly on your own -- you shouldn't call it
"work", and whatever you call it you will have to explain what it is and
why we should care.

Recommendation:  Fixating on work is a blunder.  Work is of secondary
importance at best.  Energy is primary and fundamental.  Pay attention
to the energy.  If "work" helps you keep track of the energy, fine --
otherwise forget about "work".