Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] rich context luncheon meat



On 01/27/2011 10:02 PM, Wendy Adams wrote:
I prefer some of the problems from the University of Maryland

http://www.physics.umd.edu/perg/abp/aha/index.html

OK, thanks for the pointer.

That's an interesting and refreshing collection of exercises.

The "pyramid" problem contains some interesting features. Part 1-a
is in some sense a plain old "rate times time" question, but it
is off the beaten path because the rate is not a simple velocity
but rather more akin to a flow rate. This illustrates a point
that Feynman was fond of making: the same equations have the same
solutions. And you need some understanding of the situation to
realize how the equation applies.
travel rate * time = distance
mass flow rate * time = mass

The "tailgating" (i.e. stopping-distance) exercise has the virtue
of being /important/. This is a real physics application. This
is literally the physics of life and death, in some cases. When
I talk to grown-ups and ask them what they learned in high-school
physics, and what they _wish_ they had learned, it is common for
them to say they wished there had been more coverage of real-world
applications such as this.

Everybody should do this problem. It's interesting, it's easy,
and the answers come as a surprise to a lot of people. And it
is /important/.

As always, IMHO it is a mistake to grade things on any single
one-dimensional axis ("one through ten" or "A through F" or
"glass half full"). Reality is multi-dimensional.

So, I would give the stopping-distance exercise high marks in the
"significance" dimension.

However, in another dimension this is still in the crawl-before-
you-walk stage, or maybe even a more primitive stage. I'm talking
about the "open-ended versus plug-and-chug" dimension, aka the
"creative versus cookbook" dimension. I observe that the method
of solution is spelled out in detail. Virtually(*) everything
you need to know (and nothing more) is handed to you on a silver
platter.

(*) There is one thing that needs to be estimated, but you
are /told/ to estimate it, so the amount of creativity and
the amount of brain-strain is infinitesimal.

As a further manifestation of the plug-and-chug nature of this
version of the exercise, it calls for a numerical answer under
only one set of conditions. There is no hint that it might be
useful to plot the answers as a function of initial speed.
There is no hint that there might be a scaling law involved.

You could fix this part of the problem easily enough.

Yeah, I know that babies need to crawl before they can walk,
and some babies don't have enough strength to roll over in
their crib, let alone crawl.

But we're not talking about babies here. We are talking about
college students. One would hope that being able to think,
without having every step of every calculation spelled out for
them ... one would hope that would be a graduation requirement.
Frankly, I would have thought it was an admission requirement.

Please don't tell me these student's "can't" think for themselves.
I simply don't believe it. Maybe you could convince me, but you
would need a ton of evidence. My evidence that they *can* think
comes from looking at the games they play outside of class, many
of which are quite open-ended, not at all cookbooky. Chess is
not a 100% good example, but it suffices for present purposes.
Even ten-year-old kids can play chess. They don't need to have
every move scripted for them. They can improvise and strategize
to meet a distant goal. Not all of the ten-year-olds like chess,
and none of them are very good at it, but they *can* do it after
a fashion.

If you had a room full of college kids who were *incapable* of
playing chess, then that would be a problem, and we would need
to discuss that problem. But I don't think that's what the
usual problem is. AFAICT the usual problem is that in their
previous years of schooling, the students have been taught that
they do not need to think in class, and indeed that thinking
mostly just gets them into trouble. This needs to change. You
can't change it overnight, but you can change it over time.

Just "going with the flow" using completely-scripted cookbook
exercises isn't good enough.

Some specific constructive suggestions can be found at
http://www.av8n.com/physics/thinking.htm