The Trampoline Effect

Abstract

The superior performance of non-wood bats is due to the fact that they are hollow rather than solid. The wall of a hollow bat vibrates like a drum when it strikes the ball, emitting a characteristic high pitched ping sound. The wall vibrates not while the bat and ball are in contact, but after the ball leaves the bat. The enhanced performance of a hollow bat is not due directly to the vibration of the wall of the bat. Rather, the enhanced performance is due to the fact that the wall bends slightly and then springs back as the ball leaves the bat. It is the springiness of the wall that gives rise to the improved performance of the bat. If the wall could somehow do its job more efficiently, it wouldn’t ping at all. The wall would then give all its stored elastic energy back to the ball, shooting the ball out at high speed, and there would be no energy left in the wall for it to vibrate.