Re: The flight of a spinning table-tennis ball

From: TimR (timothy42b_at_aol.com)
Date: 06/09/04 

Date: 8 Jun 2004 23:22:25 -0700

Okay, here's my understanding.

Areas of low and high pressure are meaningless. They aren't large
enough in magnitude to affect the flight of the ball and they are a
consequence of the motion, not the cause.

Without showing the math, which means this post is completely
worthless, here's what happens.

A ball spinning counterclockwise seen from above and moving forward
will curve to the left. That is obvious from experience. That is
because as it spins it collects some air (through entrainment next to
the boundary layer) and tosses it back and to the right. Throw the
air in one direction, get a reaction force in the other, basic Newton.
 I'm guessing, but it seems likely that the way you apply that force
to the air you are throwing is by shear, viscous forces. Since the
air moves, a pressure gradient develops also, but it is secondary and
has little impact on flight of the ball.

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