Re: transfer of momentum

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

Are you dealing with gen-ed students?  Yes, I do say 'if the velocity of the
object changes' -- but how do they recognize if that is the case--by
recognizing that the object has sped up, slowed down, or changed direction.
So, the mantra is repeated often--does the object speed up, slow down, or
change direction?  When looking at the Work Energy Theorem (you have a
subtitle for this one, I know) where the Net Work = change in KE, again we
look to whether the object has sped up or slowed down.   All of this is to
stay within the realm of student's instinctual knowledge of motion--does it
move, does it speed up, does it slow down, does it change direction--and
then to try and develop a Newtonian view of all this.

Rick


----- Original Message -----
From: "John Mallinckrodt" <ajm@CSUPOMONA.EDU>


> > BUT......
> >
> > The important feature here is when the momentum changes.  How do you know
> > when the momentum changes?  Answer--if the object speeds up, slows down,
or
> > changes direction.
>
> I would say, "If the velocity of the object changes."
>                                              ^^^^^^^
>
> > Now if using acceleration, one asks:  "How do you know if the object is
> > accelerating?"  Answer--if the object speeds up, slows down, or changes
> > direction.
>
> I would say, "If the velocity of the object is changing."
>                                              ^^^^^^^^^^^
>
> The difference may appear minor, but I believe its pedagogical effect
> is not at all subtle.
>
> --
> John Mallinckrodt        mailto:ajm@csupomona.edu
> Cal Poly Pomona          http://www.csupomona.edu/~ajm