Re: transfer of momentum

[Joseph Bellina <jbellina@SAINTMARYS.EDU>]

I agree with your suggestion.  I also think we should not use Newton's
original work, just as most have found they can't use Feynman's text.

I wonder what would happen if we eliminated the work acceleration and
only used change in velocity, or if you wanted change in momentum.  By
eliminating the work you would eliminate the task of developing a
conceptual understanding for it.  I would also like to eliminate the
word displacement, since it is just the change in position.  It seems to
me that students can handle vector position and vector velocity pretty
well.  They can do change in position and change in velocity too,  but
vector acceleration, the change of a change is just too much
for many of them to conceptualize.  I'd rather just talk about the rate of
change of velocity, or of momentum.  The term displacement is, in my mind,
superfluous.

cheers,

joe

On
Wed, 19 Nov 2003, Chuck Britton wrote:

> If I understand John correctly -
>
> He is trying to DOWNplay the equation that most of us rattle off as N2, F=ma.
>
> A MUCH better representation of Force is Newton's own version
>
>         F = delta p/delta t
>
> Even for those intro students who are being introduced to SR (or GR),
> it is VERY good pedagogy to use the momentum formalism in favor of
> the acceleration approach.
>
> Most of us realize how much trouble acceleration causes for our students.
>
>         Example - a ball at the top of it's trajectory. What is the
> force/acceleration of the ball AT THAT INSTANT!!!
>
> If you think that most of your student 'get this' you are sadly mistaken.
>
> Drawing a momentum vs time graph (or more commonly,velocity vs time)
>
> Gives them a visual picture that answer the difficulty for some/many students.
>
>
> Acceleration is a VERY difficulty concept.
>
> Momentum is a MUCH simpler and basic concept.
>
> USE it ! ! ! !
>
> OK, ya'll, at 9:56 AM -0500 11/19/03, Bob Sciamanda wrote:
> >  I respect your free choice to use this conceptual model of F=ma in
> >  component form.  As with all conceptual models, this is a matter of
> > taste and free choice;  the testable physics lies in the quantitative
> >  relations connecting measurables.
>
> --
> Chuck Britton                                   Education is what is left when
> britton@ncssm.edu                       you have forgotten everything
> North Carolina School of Science & Math         you learned in school.
> (919) 416-2762                                  Albert Einstein,        1936

Joseph J. Bellina, Jr.               574-284-4662
Associate Professor of Physics
Saint Mary's College
Notre Dame, IN 46556