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Re: little gee and its sign



At 9:36 -0600 9/12/01, Jim Green wrote:

At 06:33 12 09 2001 , you wrote:
I've always thought g was the local gravitational field.
skip

Oh my. Folks we are talking about an intro class and the first few weeks
of the class with the introduction of the topic of dynamics -- and you want
to present the concept of a field????

Quite so, if one starts the intro. physics course in the traditional
manner. I suggest an alternative.

Acceleration is not an easy concept to grasp at the beginning. It's
not very intuitive, and certainly is an abstraction. So why not start
with uniform motion and then introduce momentum as the starting point
for dynamics? Momentum is, it seems to me, much easier to motivate
and is much more of a concrete concept than is acceleration.
Furthermore, when one looks at momentum changes, one is led quickly
to a very useful operational definition of force, which then
dovetails nicely with Ludwick's observation that acceleration has the
same sign as the force. This make acceleration a much more concrete
idea, and certainly much better motivated that when it is introduced
in a more or less ad hoc manner in connection with kinematics.

Doing it this way, by the time one gets to the concept of "g," the
introduction of the word "field" is not so big a leap, and it
certainly prepares the students for its later use in the E&M part of
the syllabus.

Hugh
--

Hugh Haskell
<mailto://haskell@ncssm.edu>
<mailto://hhaskell@mindspring.com>

(919) 467-7610

Let's face it. People use a Mac because they want to, Windows because they
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