Aerodynamics of the Wiffle Ball

Let nobody fool you. Wiffle Ball is deadly serious. Not a realm just for kids in a field or city streets, there are some serious adult level Wiffle Ball leagues across the country. As with the physics of how much a curveball in baseball actually curves, the dynamics of how the multitude of trick pitches work when tossing a Wiffle Ball requires equal analysis comparing how hollow, perforated Wiffle Balls curve compared to the solid baseball.

We skewered some baseballs and Wiffle balls and used a wind tunnel to measure the forces “lift, drag, and side or lateral forces” as functions of things like the airspeed and spin rate. For the Wiffle ball, we also varied the orientation of the ball with respect to the airflow, making our own version of the manufacturer’s pitching instructions.

With perforations on either side of the ball, we found that the Wiffle balls experienced a lateral force that generally acted to push the ball toward the position of the holes. Things got more complicated when the perforations were on the upstream portion of the ball. As shown in the first image below, fog traces the airflow over a ball with the holes facing the flow, with a symmetric wake pattern suggesting that if we untethered the ball it would fly straight. The second image shows the flow over a ball with its holes facing up, and a wake that is deflected upward, meaning that the ball is experiencing a downward force.

I would be equally interested in learning the dynamics of how the hollow, thin Wiffle Bat impacts distance of hitting a Wiffle Ball when compared to a bat that was different in structure.

Photo Source: The Contentious Physics of Wiffle Ball

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