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Re: Scientific method was physical pendulums/ an opportunity



Leigh Palmer wrote about a week ago (sorry I can't keep up with you folks)
in connection with a golfball range problem:

The ironic thing about the problem I quoted is that the person
who made it up felt it necessary to specify the value of g. If
the student is guided by that he will solve the problem somewhat
inelegantly, but I can't make my students (who must already have
done such problems in high school) see that there is merit and
beauty in the elegant solution.

This led me to ask the following questions:

(i) In this message does "elegant" mean "algebraic" and "inelegant" mean
"numerical?" Surely the amount of work required to solve this problem is
not less for the algebraic method. In fact, one could argue (and this is
just what many of my students do) that it is the numerical method which is
less work because you only have to carry a simple value from step to step
in your solution, rather than an often cumbersome algebraic expression.

Yes, the amount of work necessary to the solution of this problem
is less for the algebraic method, if only because "g" need not be
entered twice. Any method will require the solution of one
quadratic equation, but the equation for distance is simpler than
the equation for time which many students find first.

I find that my students frequently calculate a number and then
write it down, only to enter it again into their calculators at
the very next step. I've shown twenty or so how to use their
calculators' memories - they mostly had no idea about how to do
so.

(ii) But maybe I missed something. Is there a more elegant *method* of
solution to the golfer problem than plowing through the component equations
of kinematics (which requires using the quadratic equation and picking the
correct root BTW)?

I don't know a more elegant method; I use components because I
use the independence of the two kinds of motion in the analysis.
Is there any other way?

To boil the issue down: I think most of us tell our students to manipulate
the equations algebraically before substituting numbers even when the
resulting final equations will never be used again. Of what value is this
for non-physics majors? Pretend I'm one of your introductory students and
try to convince me.

That's easy. You won't be allowed to use a calculator on the
exam (which they've known since the first day of class). I will
expect you to be able to do it my way.

I have a real tactical problem here. My exam on Friday will be
held in a room with 335 seats. I have 304 students still left
in the course! I couldn't possibly allow them to use their
calculators; I would be unable to enforce a ban on programmable
calculators with text and formula storage capability. As it is
my TAs and I will have to get very glowery to reduce wandering
eyes.

Leigh