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Re: [Phys-L] raising the game



On 07/01/2013 08:00 PM, Paul Lulai wrote:
There are times when it is appropriate to guide a student through a large problem.
There are times when it is appropriate to have students do a portion of a larger problem.
There are times when it is appropriate to have the student do larger, unstructured problems.
To choose a single item along any of these lines and point out its faults is simply silly.

We agree it would be silly to obsess over any particular example.

However, there is larger game afoot, having to do with /balance/.
Questions of balance should never be centered on any particular
example, but rather on the statistics of an ensemble of examples.

There is a sub-issue of how one might shift the balance, but
this is a sub-issue. It was illustrated, more-or-less
imperfectly, by Σ- the example.

We agree that /sometimes/ it makes sense to discuss this-or-that
principle in isolation, and sometimes not. I said this very
explicitly, so I don't think I was being silly.

I have asserted that the FCI is not well balanced. I've never heard
anybody argue otherwise. If you want to argue that the FCI does have
a well-balanced mixture of narrowly-focused problems plus larger,
unstructured problems, you have to actually /make the argument/.

Focusing on one particular example will not make the balance issue
go away.

=============================================

Having said that, here are a couple of tangential remarks on the
Σ- example:

1) On the scale of things, this isn't a bad exercise:

1a) A Σ- is not something you encounter every day, but it is a real
thing, and it really does decay into a neutron and pion. The
more you think about this reaction, the more you understand it.
You can use real-world outside information ... including e.g.
more-accurate data on the masses:
http://hyperphysics.phy-astr.gsu.edu/hbase/particles/baryon.html
http://hyperphysics.phy-astr.gsu.edu/hbase/particles/sigma.html

1b) By way of contrast, consider the monkey-shooting exercise:
The more you think about it, the less it makes sense. It supplies
a lot of context, none of which is useful. That is, you cannot
use anything you know about real monkeys, real gun physics, real
hunting procedures, et cetera. To the extent that monkey-shooting
/indirectly/ illustrates a principle of physics, the principle
is far better illustrated by other phenomena.

2) Because Σ- decay is a real thing, you can use it in a number of
ways:
-- You can make the exercise more open-ended, less pluggy/chuggy,
by providing fewer hints in the statement of the question.
-- Or you can move in the opposite direction, taking the structured,
step-by-step approach. That is, you can structure the problem in
two parts: The first part is the original version that asks for
a derivation of the equation, and the second part asks for a
numerical solution of the equation.

I still do not think it is "silly" to solve the equation after it
has been derived. Doing it numerically is ridiculously easy. It
is easier to just do it than to make excuses for why you didn't
do it.

Once again it's a question of balance and perspective. If you're
going to teach students to make 3D graphics using Vpython, then
you can't turn around and say it's not worth the trouble to solve
one algebraic equation in one unknown using a spreadsheet. It's
just not consistent.