Authors: Dylan Snook, Anthony Cornwall, Travis Ficklin
Mentors: Travis Ficklin
Insitution: Utah Tech University
The purposes of this study were to (a) experimentally measure the moment of inertia of a regulation baseball and (b) use the same method to measure the new moment of inertia of a modified baseball about orthogonal axes. The moment of inertia (I) of a rolling sphere follows the form I = k*m*r2, where m = ball mass, r = ball radius, and k represents a constant specific to the ball. Because baseballs are multi-layered of varying densities, they were not treated as a solid spheres.
The balls were rolled multiple times down a plane inclined at 4.55 degrees and acceleration was derived by video tracking the ball using a camera with optical axis perpendicular to the plane of the ball’s motion. Position and velocity were derived during the rolling acceleration, and the slope of velocity was taken to be the rolling acceleration (acc). This was then used in the equation: k = (g sin(theta)/acc) – 1, where g is the acceleration due to gravity and theta is the angle of inclination of the plane. The variable k was calculated based upon average acceleration over many rolling trials and then used to finally calculate I for each ball. Results for the regulation ball and for the modified balls will be presented for multiple axes.