Re: New AP Physics Convention in Thermodynamics

[Ludwik Kowalski <kowalskiL@MAIL.MONTCLAIR.EDU>]

Easilly available "plastic money" puts many young people
in debt. Should the traditional convention "money I have is
positive, money I owe is negative" be changed? No, I am
not suggesting this; it is good to have stable conventions.
Ludwik Kowalski

Brian McInnes wrote:

> Arnold Arons wrote in "Teaching Introductory Physics"  (page 147, 1997 Ed):
>
> "Delta E  =  Q + W
> Note that this form alters the sign of W from that used in the usual
> American convention in the first law.  I suggest this convention for the
> sign of W, at least temporarily, since it would be very messy to give
> negative signs to work done by the force in accelerating an object at a
> stage when students are having great difficulty with interpretation and use
> of algebraic signs in general."
>
> In a footnote Arons notes: "In the most commonly used American convention,
> work is taken to be positive when it is done by rather than on the system.
> This is very likely motivated by the convenience of associating a positive
> value of dW with positive values of pdv for expanding fluid (or so-called
> chamical) systems.  the convention is the reverse in much European and some
> American thermodynamic literature."
>
> Brian McInnes