Impact of a ball with a bat or racket

The collision of a ball with a baseball bat or a tennis racket is usually modeled in terms of rigid body dynamics, assuming that the hand exerts no impulsive reaction force on the handle during the collision. In this paper, a uniform aluminum beam was used as an idealized bat or racket, in order to examine both the rigid body approximation and the assumption that the hand force can be neglected. An aluminum beam was chosen so that its length and stiffness could easily be varied and so that the results could be compared with solutions for a flexible beam. It was found that rigid body models of beams, bats, or rackets are of limited use but the hand force can usually be neglected. The flexible beam model provides remarkably good agreement with experimental results and provides new insights into the dynamics of this type of collision, including the nature of the sweet spot. © 1999 American Association of Physics Teachers.