9 th Conference of the International Sports Engineering Association (ISEA) Spin of a batted baseball

Experiments are conducted to investigate the spin o f a baseball undergoing an oblique collision with a bat. A baseball was fired horizontally at speeds up to 120 mph onto a 3"-diameter cylinder of wood that was r igidly attached to a wall. In one experiment, a two-wheel pitching machine was used in which the backspin or topspin of the incident ball could be adjusted. In another experiment, an air cannon was used to project the ball with no spi n. In both experiments, markers on the ball were tracked with high-speed video to determine the velocity and spin vectors, before and after the scattering. Our primary resul ts are as follows: (1) For a given angle of incide nce, the scattered spin is nearly independent of the incident spin; (2 ) The spin of the scattered baseball is considerabl y larger than expected for a model whereby the ball rolls before leaving the surface. Implications for the spin of batted baseballs will be explored.