A couple of comments on Roger Pruitt's notes from yesterday:
1. You say "To a physicist, both acceleration and force are real
observable quantities." Yet, with the exception of forces on one's own
person none of your examples involve direct perception of *force* on
*another* object. All of them involve inferring force from the perception
of something else: spring end displacement, motion of some sort, etc. What
some of us have been trying to say is that force is *not* directly
observable, especially in situations in which we believe force is acting on
another object. All of your examples support our contention. Further, if
we get to analyzing why we believe force is acting on ourselves
(considering the neurobiology of sensation) or to analyzing what people
*conclude* about force from their own experience, then this is another
matter, BUT it does not appear that *even in this context* that force is so
obviously directly perceived as opposed to being a construct.
....and then, one is also tempted to wonder at so absolute a statement
concerning force when one is also aware to the implications of general
relativity, a theory which seems to be telling us about motions which are
*not* the result of forces. ...are there really *forces* in QM? ...is
there *really* motion of objects in QM? ...are forces really so real and
directly perceivable in physics? ...hummm...
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. It is as abundantly clear
that telling students what force *is* works for VERY few students (results
in subsequent evidence that they actually have changed their understanting
of the nature of force) and those few students who do could be modifying
their view in spite of our telling them. 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. If it really *is* the
students' views that we would like to see changed, then I think we'd better
seriously consider the general program I have suggested several times
recently in notes to phys-l.
2. In your other note, you ask (for reasons I can only guess) do we
produce better engineers with an approach like Workshop Physics? Just
because you have seen no data presented, does not mean that some exists.
Of course, Dickinson College does not produce engineers, but it does
produce physics majors. I bet if you actually asked for "data" from
Priscilla Laws or others who are trying to use the approach you would find
some "light on the subject."
It sounds to me like you are saying that we should continue teaching
physicists and engineers the same way, yet, if anything the person who made
the decision to construct the overhead walkways differently than designed
took physics taught in the traditional way. The presumption that appears
to be behind the recommendation to keep teaching them the same way is that
it actually 'works.' Obviously, if everything is okay then why change?
The problem, in my view, is that everything is not okay and furthermore I'd
like to see us do better. Hence, I don't agree with the suggestion for
that reason as one among several other important ones.
It also sounds like you are saying that all the rest of the students who
experience physics instruction are less important. One might be able to
take this position if what we do to prepare engineers and physicists had no
effect on the rest of the population. The trouble is that it does affect
the rest of society. Just to point to the most proximate effect: If the
person making the construction site decision about the walkways was not an
engineer who took physics in the traditional way, then it was a
construction manager who took either physics for engineers or an
algebra-trig level intro physics course.
For the by far bigger effect on society, I point to the fact that probably
the MOST LASTING lesson learned by people exposed to physics instruction is
that there is something they *cannot* do; i.e., make sense of the physical
world. This lesson is by far the dominant one over time and in relative
'weight' for 99+% of the population. It is learned very early in school
life. It would be one thing if it were true. If it were true, it still is
nothing to be proud of. BUT, it is *not* true. I'm not saying that
everyone can "do" theoretical physics, but I am saying that people can make
more sense of the physical world than they do via physics instruction than
they do now and at a much earlier age than most who teach physics think
they can. This makes the situation all the more horrible that this ONE
LESSON is the main one taken from the enterprise of physics teaching as we
generally know it today. (I will add that it is not even a desirable or
responsible lesson that some learn that the "can" do physics and most
others cannot.)
One might still be tempted to focus on the notion that we cannot 'cover' as
much material by "the Workshop Physics" approach. To this I ask, why do we
have to wait until college to accomplish all this stuff? Much of this
could be accomplished before or by the 9th grade, but all of the teachers
come to the university and get taught the traditional way. But they could
be taught differently, yet *we* do not do this. In a better world, if we
choose to make one, I can imagine that students would have done alot or
most of the conceptual front end by the time they get to college and in
doing so would not only have changed their initial notions, but the major
lesson would NO LONGER BE that *they* cannot make new sense of the
phenomena. Now that I could live with much better!
Dewey
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Dewey I. Dykstra, Jr. Phone: (208)385-3105
Professor of Physics Dept: (208)385-3775
Department of Physics/SN318 Fax: (208)385-4330
Boise State University dykstrad@varney.idbsu.edu
1910 University Drive Boise Highlanders
Boise, ID 83725-1570 novice piper
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