Abstract
The purpose of this study was to examine kinematic factors (swing speed, angular speed of the bat, impact position, center of rotation of the bat, etc.) influencing batted ball speed in baseball. Applying the law of the conservation of angular momentum, we derived a computational formula to determine batted ball speed for given kinematic parameters. A series of computational simulation were conducted to clarify the influence of each of these parameters to the batted ball speed. The simulation outcome demonstrated two characteristic phenomena: One phenomenon is that, batted ball speed decreases without altering the bat head speed when the angular speed of the bat at impact is reduced (in this case, the center of rotation of the bat was shifted away from the center of mass); and the other phenomenon is that, the impact position of the bat that maximizes batted ball speed deviates slightly from “the sweep spot“ toward the bat head when the angular speed of the bat at impact is increased without altering the bat head speed (the center of rotation of the bat was shifted toward the center of mass of the bat, in this case). These phenomena can be explained only when the coefficient of restitution of a bat is not uniform across different positions over the bat surface as well as across various swing characteristics, such as angular speed of the bat and the center of rotation of the bat.
