Re: Why work before energy in texts

[Bob Sciamanda <trebor@VELOCITY.NET>]

> Is is correct to say that work "becomes" energy, rather than "produces"
> energy or "results in" energy or some other way of describing the
> sequence?

This is of course the language of conceptual models.  There is work and
there is work.   Eg.: in a commonly used conceptual model, when a single
force accelerates a single particle, useful meaning attaches to the view
that a transfer of energy occurs from "forcing agent to the accelerated
particle".  On the other hand the (CM) work done by the rigidity force of
a wall on a skater who pushes off from that wall is a numerical measure of
the KE change in the skater, but the wall is not the source of that
energy;  energy transformations are here internal to the skater. The CM
work energy theorem remarkably monitors that internal energy exchange from
the work of only external forces.

The above is concerned with work within the scope of Newtonian mechanics.
Further confusion arises when the first law of thermo uses (a more
generally defined) FdX term, calls it work and equates it to an energy
transfer across an indicated boundary. People then want the mechanical
work integral to always play that same role - it does not.

Bob Sciamanda
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor