Re: What produces the curve in a wiffle ball pitch?

Anna

Wiffle balls are very interesting from a Physics perspective and as you
have found, the aerodynamics are pretty complex.

Solid surface balls such as baseballs or soccer balls curve due the Magnus
effect (http://en.wikipedia.org/wiki/Magnus_effect).  The Magnus effect
explains the curving path a spinning object takes as it moves through a
fluid, in this case air.  Imparting a spin causes one side of the ball to
create a low pressure area, much like an airplane wing, and the higher
pressure on the other side of the ball pushes it towards the low pressure
side.  

The curve in the path of a wiffle ball is driven more from an aerodynamic
drag, or wind resistance, perspective than the Magnus effect.  The holes
are located on only one side of the ball to increase the drag on that side,
causing the ball to curve towards the side with the holes even when there
is very little or no spin.  The holes are oblong to maximize this
aerodynamic drag.  

If the holes were evenly distributed around the ball, the aerodynamic drag
would be equal on both sides and any curving would be the result of spin
and the Magnus effect. 

Good Luck