THE SCIENCE OF THE WIFFLE BALL. This article by Bjorn Carey in Popular Science reports on research using a wind tunnel by mechanical engineer Jenn Stroud Rossmann at Lafayette College on the forces that operate on a Wiffle ball. (A Wiffle ball is a hollow plastic ball with holes on just one half of the surface.) The results are satisfyingly complicated. The path of the ball is determined by the net effect of external and internal forces that shift constantly as the ball is in flight. External forces result from disruption of airflow over half of the ball, while “air rushing into the holes creates vortices that whirl inside.”
I never had much control of a Wiffle ball. I tried to make the ball spin parallel to the “equator” line on the ball and throw side arm. There was one wonderful day when I could make the ball dip or rise sharply and predictably, but I never was able to do it again.
It’s nice to learn that a knuckle ball can be thrown with a Wiffle ball with the same unpredictable results as with a baseball and in the same way—by throwing the ball with as little spin as possible. The holes on the Wiffle ball should face the batter upon release.