If I read the responses correctly, we are agreed (with the exception of
Mike Maloney) that spinning balls curve in the direction of the spin. The
standard Bernoulli description (again with at least one exception--early
editions of Ostdeik and Bord) predict the curve to be in the direction of
spin. I think the justification for adding and subtracting the air
velocities has to do with getting the NET air flow close to the surface of
the ball. I'm not sure how that melds with a streamline description of the
phenomenon.
P.S. Maybe Roger Haar's description of what gives a right-handed pitcher
the advantage over a left-handed batter is better than MY ASSUMPTION that a
curve would move away from the batter. Then the fact (from David) that a
right handed pitcher's curve goes IN to a left handed batter is OK. I just
had figured it was easier to hit a ball that was AT LEAST within reach than
one that moved away out of reach. I haven't played baseball since I was 10
and back in those days all the pitchers worried about was getting the ball
anywhere near the plate! ;-)
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Richard W. Tarara
Department of Chemistry & Physics Free Physics & Energy Instructional
Software
Saint Mary's College available at:
Notre Dame, IN 46556
219-284-4664 http://estel.uindy.edu/aapt/rickt/software/
rtarara@saintmarys.edu http://www-hpcc.astro.washington.edu/mirrors/tarara/
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