Re: correct answer

[John Mallinckrodt <ajmallinckro@CSUPomona.Edu>]

On Thu, 9 Oct 1997, Dewey Dykstra, Jr. wrote:

> This, I believe, is the type of problem which first motivated Bruce
> Sherwood to realize that the standard form of the W-E Theorem presented in
> the C.M. frame does not work in this setting.  The object is deformable.
> His subsequent considerations led to (I believe) 2 AJP articles whose exact
> references I do not have at my finger tips.  Maybe someone else remembers
> them.

  "Pseudowork and real work," Am. J. Phys. 51, 597-602 (1983).

and, with William H. Bernard) 

  "Work and heat transfer in the presence of sliding friction," 
  Am. J. Phys.  52, 1001-1007 (1984). 

In the first article, Bruce drew the important distinction between the
usual definition of work--force times displacement of the point of
application--and what he called "pseudowork"--the work that *would* have
been done by the force *if* it had been applied at the CM of the system on
which it acts.  This "pseudowork" is the work that Bob Sciamanda regularly
alludes to as the only appropriate work to use in "the" work energy
theorem.  It is always, trivially, the case that the total pseudowork on a
system is identical to the change in the center of mass kinetic energy of
the system. 

In my paper with Harvey Leff,

  "All about Work," Am. J. Phys., 60, 356-365, (1992).

we showed that there are at least *seven* useful definitions of work (with
two of them turning out to be identical) and *six* useful "work-energy
theorems" (one of which is, of course, the pseudowork-CM kinetic energy
theorem.) 

Why does it feel like we've been through this before?

John
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