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Re: transfer of momentum



"Mechanics and Heat" by Frank (McG-Hill about 1940) was, I believe, the
text used both by Feynman and myself (at least we have that much in
common). It starts with change of momentum.

On Tue, 18 Nov 2003, Chuck Britton wrote:

Our school has been using the momentum approach to force for several
years now. The word Force isn't discarded but it IS reserved until a
thorough treatment of momentum has been covered. (Acceleration spends
ALL of the first quarter and into the second as being ONLY the slope
of the velocity graph.)

After momentum and collisions (including elastic collisions analyzed
from the CM reference frame) the idea of force being what happens
when the momentum changes in the collision seems quite clear. Impulse
approximation calculation fit right in smoothly.

I must admit that I have never considered the FLOW of momentum but it
certainly fits into the newtonian view. (Newton NEVER wrote F=ma).
His second law 'relates' the change of momentum to this thing called
force. (net Force)

Text books are a bit slow at picking up on this pedagogical
'breakthrough' but I believe that Chabay & Sherwood have adopted this
sequence. (momentum before energy etc.)


At 6:09 PM -0800 11/18/03, Ludwik Kowalski wrote:


Radical ways of teaching should first be tried as
simulations; for example, by writing a physics
textbook based on new ideas. Then in very small
experimental classes. Throwing away the concept
of force is dangerous; we might replace it by a new
concept and be very sorry later. I would strongly resist
if somebody tried to force me to implement a radical
change, such as replacing F by dp/dt in dealing with
static situations. I would have to see some simulations
(textbooks), I would have to hear from teachers who
experimented with new ideas on a small scale.
Ludwik Kowalski


--
I never teach my pupils; I only attempt to provide the conditions in
which they can learn.
- Albert Einstein


--
"Don't push the river, it flows by itself"
Frederick Perls