Spin from Oblique Impact of Batted Sports Balls

The spin of a batted ball is needed to describe the ensuing trajectory. The following considers experimental spin measurements collected by impacting a stationary ball with a swinging bat. Each collision was recorded with two high speed cameras from which velocity and positional data was obtained. Both baseballs and softballs were hit at swing speeds from 28m/s to 39m/s producing ball trajectories from 0° to 25°. The effect of hit angle, barrel surface friction, bat circumferential moment of inertia, barrel diameter and ball inertia were observed using four different bat constructions and two different ball types. Ball spin increased with hit angle and bat speed, and decreased with ball inertia. Ball spin was not influenced by barrel surface friction, barrel diameter, or bat circumferential moment of inertia.