Aerodynamics of tennis balls - effect of wear

The aerodynamic properties of spinning balls were obtained using a wind tunnel with a dedicated force balance. The ball was spun at rates of up to 2750 rpm, which is representative of a typical top spin shot hit by a professional player. Drag and life coefficients (CD and CL respectively) were measured for a range of balls which had been subjected to varying amounts of wear. Both CD and CL of the worn balls were generally lower than those of the new balls. A trajectory plot was used to show that the heavily worn balls would give a receiver 1.5% less reaction time.