Re: [Phys-l] [ap-physics] The Swinging Bucket Problem

["John Clement" <clement@hal-pc.org>]

Actually it really doesn't work well for college students either.  Only the
top tier may understand the meaning of "centripetal force".  By the top tier
I think it is between the upper 1 and 5%.  As a result completely omitting
the words centripetal and centrifugal is very advisable.  In the intro.
course the forces need to be treated as always something produced by
physical agents or interactions.  Then the net force is used in NTN2.  But
there is the suspicion that even the term net force is a barrier, but that
the term sum of the forces might be better.

The fact that students tend to regard "the centripetal force" as a
particular force has been noted by the researchers, and it is a strong
misconception.  Following Arons one should never introduce the term
"centripetal force" until after the concept has been explored that the net
force can produce circular motion.  At that point it only needs to be
introduced for students who might go on and need to read other physics
books.  It is totally unnecessary and confusing for the other students.  So
why not just defer it until the concepts are thoroughly mastered, say at the
end of the semester.  And of course the top tier will figure out the term if
they read another book, without your introducing it.

John M. Clement
Houston, TX

> Because it works for millions doesn't mean it will work for my high-
> schoolers.  The top of the class would be fine with centripetal.  The
> students that are not planning on going into a science field, or for that
> matter going to college, sometimes need something a bit different than
> what might be accepted by millions.
>
> If my students go to Dictionary.com & look up centripetal, the first
> definition they see is:
>
> centripetal force:  the force, acting upon a body moving along a curved
> path, that is directed toward the center of curvature of the path and
> constrains the body to the path.   (there are additional definitions that
> are a bit more accurate).
>
> They read "THE force" to mean the ONE force that is making this happen.
> We can all agree this is not true.  It would certainly be nice if a single
> class discussion would resolve this issue, but it doesn't (ok, it does for
> the top tier, but I can just give the top tier the book & they'd be able
> to figure it out)..