Performance versus moment of inertia of sporting implements

A review is presented of the importance of the moment of inertia (MOI) to the performance of a sporting instrument. It is shown that for a given coefficient of restitution (COR), both the intrinsic power and the swing speed of a tennis racquet or baseball bat correlate strongly with the MOI about an axis through the handle and only weakly with the mass. It is further shown that for non-wood baseball bats approved for use in college baseball in the USA, batted ball speed is a stronger function of COR than of MOI. When comparing two implements with the same MOI, the primary factor affecting performance is the COR, which can be enhanced by means of the trampoline effect. A new method of matching the MOI of a set of golf clubs is also described. r 2009 John Wiley and Sons Asia Pte Ltd