[Phys-L] Re: taking stuff apart

["Dwight K. Souder" <crvhs_dks@CRESTVIEW-RICHLAND.K12.OH.US>]

You brought up some good points and ideas.  The part about how much students
will learn from the experience, I'm also thinking of the idea of where the
students must make their own simplified, working model of their device.  I
figure for a student to take something apart, study it, and understand it
well enough that they could turn around and make something of their own and
present it...their is going to have to be some higher level thinking going
on.  One example I have was several years ago, I made my own pendulum &
weight driven clock all from wood.  One of my "weaker" students was so
interested in it, he studied it for a while, taught himself a little bit
about gears and pendulums, and made a simple clock out of cardboard that he
laminated himself.  I was impressed!  I even caught him a couple of times
doodling new designs.

My other reason for these projects is that there are a lot of stuff we use
on a daily basis that we have no idea of how or why they work.  To many of
the students, it's "magic".  Many do not realize that many of the machines
we have are rather simple, but put together in complex ways.

I was also at a science museum and one of the displays were all of these
"gadgets" people made.  There were some interesting and large number of
these gadgets, until the rise of TV...then the number of gadgets made
quickly dropped.  I think it's sad that more students don't "get their hands
dirty" more often and try some creative things with parts that are readily
available.

Please, if anyone has anymore ideas/suggestions of what to do or how to go
about presenting and assessing such material, it would be greatly
appreciated!

Have a great day!
Dwight


-----Original Message-----
From: John Denker [mailto:jsd@AV8N.COM]
Sent: Thursday, September 29, 2005 4:35 PM
To: PHYS-L@LISTS.NAU.EDU
Subject: Re: taking stuff apart

Dwight K. Souder wrote in part:

> The second type of project is a "How does it work project", where students
> pick a complex mechanical device and figure out how it works (for example:
> wind-up clock, combination lock, etc.).  The students then make a
> presentation of their device and how it works.

1) The general idea of taking stuff apart to see how it works is
excellent.  However, there are a number of devilish details.
If you don't attend to the details, it will be much less of a
learning experience.

As is all too common, it is something of a double-or-nothing
situation;  the smart kids will learn a lot from the experience,
and the not-so-smart ones will learn much less.  Taking stuff
apart is easy;  taking stuff apart in such a way that you learn
from the experience is trickier.  It helps if you already have
a pretty fair idea of how the thing is supposed to work;  then
you can identify the parts as you find them.

1) Here is a suggestion that isn't as crazy as it might sound
at first:  A good starting place involves taking apart a junk
computer (obsolete and/or broken).  When you do this with
young kids, forget the fact that it was ever a computer and
concentrate on the fact that is is a box with a very nice
modular power supply inside.  Get rid of everything but the
power supply.  The result is that the kid has a closely-regulated
power supply that puts out +3.3V at a lot of amps, as well
as +5, +12, -12, and perhaps a few other things.  The pinout
for the widely-used "ATX" power supply connector can be found at
  http://xtronics.com/reference/atx_pinout.htm

Hint:  3.3V is great for electrolysis of water.  When I was
a kid, I was stuck with 12V battery chargers and "train"
transformers, and 12V is just way too much:  it causes lots
of nasty side-reactions.  I would have been super-overjoyed
to have something even remotely as nice as an ATX power supply.

2) Once you have the power supply, it expands what you can
do when taking other stuff apart ... because you use the power
supply to power-up various subsystems and see what they do.
A good example of this is taking apart a junk VCR:  if you
apply power to the load/unload motor, the mechanism will go
through its whole cycle, which is mind-bogglingly complex.
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