🚀 go-pugleaf

An intro  I like to use to put students into the "woderment/
thinking" mode uses a 'kelt'.  This little oblong pices of plastic
spins very smoothly , like a top in counter clockwise direction.
However most right handers will try to spin it in the clockwise
manner, where up on it will. wobble, come toa stop and proceed to
rotate in the opposite direction.

With a little misdirection it is easy to demonstrate a smooth
rotation, rub it magically to change its 'internal orientation'
and hand it to a student. The frowns on their faces when it does
its truck is truely rewarding.  I take it back, rub it some more and
again spin it in its stable mode.

After first diposing of the notion that physics teachers have specail powers,
student will ususally hypothesize that the direction of motion is a
simple explanation, go on to discover that the  kelt is assymetrical,etc.

The kelt actually stores rotational energy in a cyclic rocking motion
before it converts the rocking motion into a counter rotataion.
An article in Scientific American discusses the dynamics of the thing
in detail. Sorry I don't have the reference handy.

There are dozens of similar teases and hooks to use to get students
attention and imagination working.
Landon Wood

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lwood@ednet1.osl.or.gov    |   Landwood@aol.com
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Grant Union H.School           John Day, OR