The Effect of Spin on the Flight of a Baseball

Abstract

New measurements are presented of the lift on a spinning baseball. The experiment utilizes a pitching machine to project the baseball horizontally; a high-speed motion capture system to measure the initial velocity and angular velocity and to track the trajectory over ~5 m of flight; and a ruler to measure the total distance traversed by the ball. Speeds in the range v=50-110 mph and spin rates (topspin or backspin)in the range omega=1500-4500 rpm were utilized, corresponding to Reynold's numbers Re=(1.1-2.4) x 10^5 and spin parameters R*omega/v=0.1-0.6. Standard least-squares fitting procedures were used to extract the initial parameters of the trajectory and to determine the lift and drag coefficients. Comparison is made with previous measurements or parametrizations of the lift and drag coefficients, and implications for the effect of spin on the flight of a long fly ball are discussed.