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Re: forces



John Mallinckrodt says:

... As Dewey says, students
can be trained to notice acceleration, but it takes a LOT of
careful work. I don't think it takes nearly as much work (in
fact, I don't really think it takes *any* work) to get students to
notice that "degree of squashing"--even of other objects--is
directly related to the amount of force applied. John Clement's
bridging analogies make effective use of students' innate
understanding of such connections.


Dewey Dykstra, Jr. says:

Finally, whether forces are so obvious to physicists or not, it is
abundantly clear that what *students* think of and refer to as force is not
the same thing as most physicists in many ways. ...
... So, I don't see either the
scientists' version of acceleration *or* the scientists' version of force
as being *either* more or less an abstract invention when one starts from
what I understand to be the students' typical view.


In my (very naive) view, I would have agreed with John that students
pre-understanding of 'force' is extraordinarily close to the physics
understanding of it. In what ways do you see a difference?

Perhaps you are refering to the concept that force causes motion (rather
than change-in-motion). In that case I understand you, but I would label
that as a pre-conception about the relationship between force and motion
rather than a pre-conception about force itself. I think that distinction
may be important, although it may be a 'nit-pic'.

--
--James McLean
jmclean@chem.ucsd.edu
post doc
UCSD