Re: Pb

[Scott Goelzer <sgoelzer@COEBROWNACADEMY.COM>]

To demo this kind of transformation I drop a steel ball onto a one of
the temperature sensitive color changing post cards (the Exploratorium
sell these). The card must be on a hard floor.  A color change occurs at
the point of impact. Pressing the ball against the card and  floor with
great force and effort causes no change in color. Dropping the ball on a
piece of wood with the card in between also causes no change in color.
Demo leads to great student discussion regarding where energy is being
transferred.

HTH
Scott

> Date:    Sat, 10 Mar 2001 23:03:19 -0700
> From:    Jim Green <JMGreen@SISNA.COM>
> Subject: Re: Pb
>
> I appreciate the responses to the dropping the lead question -- especially
> the comments of John Denker.  I was having trouble correlating the
> ice-skater-into-the-wall situation with the lead-hitting-the-floor
> question.   After John's comments, I realize that I must have been having a
> senile attack.
>
> The key is that the wall/floor does "no" work -- that the body/lead does
> the work on itself.  Note that if one were to drop a hard steel ball on a
> hard floor the story is somewhat different -- except that if the ball and
> floor were real, the same amount of work would be done on the object by the
> time the object came to rest and would be heated just the same.  A nice
> thought experiment.
>
> Thanks all
>
>
> Jim Green
> mailto:JMGreen@sisna.com
> http://users.sisna.com/jmgreen
>
> ------------------------------

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Scott Goelzer
Physics Teacher
Coe-Brown Northwood Academy
Northwood NH 03261
sgoelzer@coebrownacademy.com
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