Re: momentum before force (was: friction)

["Daniel L. MacIsaac" <danmac@physics.purdue.edu>]

Whoops.  I just posted:

> Newton worked in dP/dt -- the change in momentum (he was too cagey to
> assume constant mass like the statement F = ma is often misinterpreted).
> From IMPETUS or the better-differentiated MOMENTUM that followed, he
> defined force.

....by this murky writing I was trying to bring up the fact that 
dP/dt = m dv/dt + v dm/dt; with which Newton was intimately aware and
which is often overlooked in our more modern treatments of F= ma in 
beginning dynamics.  We tend to leap at F = m dv/dt right away, which is
incomplete.  Newton's language was very cagey about this; better
than most of our own textbooks. However, a distinct idea of P evolved 
BEFORE F by some considerable time.  No co-evolution here, one distinctly
precedes the other.

Dan M
(momentarily avoiding drawing up my second exam for today :^)

Dan MacIsaac, Assistant Professor of Physics and Astronomy, Northern AZ Univ
Visiting Asst Prof, Purdue Univ;  Adjunct Faculty, Indiana Univ at Kokomo
NEW NET ADDRESSES:  danmac@nau.edu  http://www.phy.nau.edu/~danmac
PhD in Education: Curriculum & Instruction