Re: plug and chug

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

----- Original Message -----

> > There has been some discussion of problems that are not "plug-and-chug",
> > but if there were any examples, I missed them.  So here are two from my
> > weekly 15 minute quizzes.  The text was "The Mechanical Universe", the
> > course was calculus based, notes and calculators were not permitted.

The following problem (or close to it) has appeared in Halliday & Resnick
through many editions and has always been one of my favorites.  There are
plenty of such problems in the text books that aren't simple p&g and can
hone critical thinking and problem solving skills (along with plenty of p&g
problems to work on the math skills).  The problem admittedly has some
'unrealistic' aspects--the completely elastic collision--but for that
matter, few of the Heller problems are all that realistic either.  Truly
realistic problems will seldom succumb to introductory course problem
solving techniques.

'A steel ball bearing is dropped from the roof of a building (the initial
velocity of the ball is zero).  An observer standing in front of a window
120 cm high notes that the ball takes .125 s to fall from the top to the
bottom of the window.  The ball bearing continues to fall, makes a
completely elastic collision with a horizontal sidewalk, and reappears at
the bottom of the window 2.0 s after passing it on the way down.  How tall
is the building?'

Rick

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Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556
rtarara@saintmarys.edu

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