Comparison of standard and oversize tennis balls for normal impacts on a racket

The coefficient of restitution was determined for two different types of oversize tennis ball for normal impacts on a rigidly clamped racket. A standard ball was also tested as a control. It was found that an oversize ball with the same mass and type of rubber and internal pressure as a standard ball, rebound with a higher coefficient of restitution. However, an oversize ball with a lower internal pressure rebound with a lower coefficient of restitution, compared to the standard ball. The quasi-static hysteresis loss of balls, determined from compression tests, correlated with the coefficient of restitution results. It was found that an increase of 7% in the ball-racket contact area resulted in a decrease of 5% in maximum string extension, for an impact with the same peak force.