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Re: .Bernoulli and curve balls.




In fact, for a slowly spinning, slowly
pitched *smooth* ball, the curve can break the opposite way as the
air flow may be laminar on one side and turbulent on the other.

The mythology is enhanced! What speed must the ball move (and spin)
so that the airflow becomes laminar? To what precision must this
condition be established and maintained?

This is obviously a pretty complicated problem.

And what do physicists do when confronted with a "pretty complicated
problem"? Give up!? Let's have a bash at it and see why this is not a
credible possibility.

.. . . some analysis follows which I omit. . .

This problem is difficult. It is also complicated. The answer is
well known, however, and that should be a guide to tell us whether we
are modelling it reasonably or not. The glib "explanations" in terms
of the Bernoulli effect are unsatisfying and unedifying in addition
to being incorrect. I can't find the Hecht explanation of the curve
ball which was cited as 98% correct and I'd like to have that page
number again (I have the Hecht books). We are *not* all agreed, though
I may be a very small minority, but at least I've done a calculation!

Leigh




There exists empirical data on this problem taken in wind tunnel
tests which I believe is reported in the Briggs article previously
cited. It confirms a curve opposite to the direction expected from
the Magnus effect and the wind velocity at which this occurs does
correspond to the transition from laminar to turbulent flow.
Evidently, then, there must be some error in the calculation (though
I must confess I didn't catch it).

Paul J. Camp "The Beauty of the Universe
Assistant Professor of Physics consists not only of unity
Coastal Carolina University in variety but also of
Conway, SC 29528 variety in unity.
pjcamp@csd1.coastal.edu --Umberto Eco
pjcamp@postoffice.worldnet.att.net The Name of the Rose
(803)349-2227
fax: (803)349-2926