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Re: force

It seems to me that force is far more observable than is acceleration. I
experience and feel forces--run into a wall or sit in a car and have it
speed up, for example. Yes, there are accelerations involved, but what I
feel are forces on me. These seem to me to directly observable--very

Here's a problem. Drop a ball on a coil spring. At what point will the
acceleration on the ball be zero? Most students and many physicists will
say that it is when the spring is fully compressed. WRONG! It is when
the net force on the ball is zero. At that instant the ball is still
moving downward and compressing the spring.

I think there might be some advantage, therefore, to teaching forces
first then kinematics. However, a better approach might be to integrate
them more than is presently done.


Why don't "we" ever consider where the students 'heads' are with respect to
forces (including what *they* think forces relate to and how and why) first
and then follow Maurice Barnhill's advice which follows?

Now granted, all the things I had done before *had gotten them to the
point that they had two sets of discordant explanations, each of which
they thought ought to be true.* THIS CONDITION IS WHAT IS REALLY NEEDED

"We" seem to be so wrapped up in"what" or "where" the students are supposed
to get that the process of how and why THEY might change the sense they
make of the world is totally ignored. If this is the case then why do we
expect any results other than those "we" get regardless of what order we
"teach" the topics?

What *is* our justification for determining "what" or "where" students must
get? ...and who does it serve?


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
1910 University Drive Boise Highlanders
Boise, ID 83725-1570 novice piper