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Re: The Good Stuff




For those who want a new thread, here are a couple of starting points.

1) I had a couple of students come up after class and ask "So, when do
we get to the _good_stuff_?" After half a semester of projectile
motion with another half a semester of mechanics to come, I was at a
lost. Presumably they want to see nuclear power, quarks, and big
bangs; along with perhaps electronics or telescopes.



I have had similar feelings about mechanics in the past especially since I,
like others who responded, have students who aren't going on to additional
physics classes. BUT, I found the good stuff in mechanics in the larger
issues of physics and it's ways of knowing (for lack of a better phrase).
For example, most students come in to my class having heard at least some
part of the ideas of what rate objects fall and how weight plays a role
(Galileo and the Tower of Pisa story), but they aren't really able to
explain it and tend to fall back on their own intuition pretty quickly when
it comes to defending the concepts they have half-learned. I have asked my
class to perform this exercise.

1) Propose an answer to the question - does the weight of an object affect
how fast it falls (Some students haven't heard it before and say yes. Some
have seen it somwhere else and say no. No one has generally thought it all
the way through).

2) Lab groups measure the time it takes several objects of their choosing to
fall from a fixed height. (The level of sophistication of this experiment
depends on which level of physics class I am dealing with).

3) We "analyze" the data graphically by plotting time and weight data
comparing everyone's results. Usually I get one of the following results
(a) Students used objects that vary widely in shape and weight and get some
appreciable differences in time measurements.

(b) Students use objects with the same approximate weight and shape and get
times that don't vary appreciably.

4) In either case, students tend to believe they have either proven or
disproven their original conjecture. Heavy objects fall faster because my
textbook hit the ground a lot quicker than a feather for example. Or, I
thought all objects fall at the same rate, but the textbook/feather
differences seem to disprove that.

5) In front of the class, I drop a piece of paper held horizontaly and a
textbook at the same time. I then wad up the paper and drop it and the textbook.

6) Students now have to consider this "evidence" and rework any new ideas
about the heavier/lighter question into their original ideas AND then
propose and perform experiments to test these new ideas. (If they struggle
in their thought process - I sometimes ask them, "Which would you rather do
- jump from an airplane with a parachute or without one? Why?).

The whole point in my boring you with this lesson plan is to show that even
though we make think of introductory kinematics as not the good stuff, there
are several important things that make the unitiated student think. These
things even make those who believe they have already been taught all about
it think. And things that make you think constitute the good stuff in my
book. Student response is pretty good too, by the way.

R. Allen Shotwell
Chair, Science and Math
Ivy Tech State College
Terre Haute, IN