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[Phys-L] Re: student difficulties with velocity as a vector?



Yes, that is a start. The learning cycle approach which has been shown to
improve students on a Piagetian test also improves student understanding.
This means first exploration, then term definition/concept explanation, and
finally application. This approach was found by Karplus and Lawson to be
very effective, however it needs to informed by research as to what
sequences work best. It has been used by the Modelers, but they call it the
Modeling cycle.

However, remember that conventional demonstrations do not work well as has
been shown by Catherine Crouch. She did find that if the demo is preceded
by prediction it worked better. One approach to improving demos would be to
get the Interactive Lecture Demonstrations by Sokoloff and Thornton, Wiley.
These are partially scripted lecture demos which work very well. The
sequence of demos and the order of operations are scripted, but the words
you say are not.

Rather than telling the students there is something strange going on, they
should be forced to conclude for themselves that something strange is going
on. Unfortunately they have such a strong attachment to their
misconceptions that they will perceive the misconception rather than the
actual event. For example, dropping and projecting a steel ball at the same
time can be readily heard to hit at the same time. Students will then think
the echo is one of the balls and the immediate clunk is the other. One way
out of this dilemma is to video it with instant replay. If the replay is
too delayed, the demo will fail, so it must be really instant.

BTW the mathematicians way of teaching vectors as a series of abstract
things is absolutely hopeless because it does not attach any of the basic
misconceptions. It proceeds in the wrong direction. The research by Lawson
and others has shown that best understanding is obtained by going from the
concrete to the abstract, not the other way around. Notice that the
learning cycle does this.

Again, I would urge people to first all get onto the same page by reading
the McDermott article, and perhaps looking at the McDermott tutorials.

John M. Clement
Houston, TX


I suppose it is way, way below a physics teacher's mien
to give a pitch like this:
"Folks, there is something very very strange going on with these two
balls.
One I drop off the edge of the bench, the other I whack sidewards.
Watch: what is strange about the time the balls take to hit the floor?"

Show not talk? Forget about 2-d vectors? Let's see the evidence
first?

Brian Whatcott Altus OK Eureka!