Have you ever dropped a ball and had it bounce once normally before taking a crazy second bounce? I'm always watching out for this phenomenon when I have a lacrosse ball on a hard surface, but I've never really understood what was going in. The main factor causing the crazy second bounce is actually the spin on the ball acquired during the first bounce. As the ball falls, it usually has a small amount of spin or is traveling at an angle that isn't 90 degrees. As the ball hits the ground, the ideal,perfectly elastic collision does not happen as there is friction between the ball and the ground. This friction is responsible for creating a backwards force of the surface of the ball, resulting in a much greater spin than before. When the ball then hits the ground the second time, the spin takes effect as the ball shoots off in the direction of the spin, reaching a low vertical displacement but far horizontal displacement. Because of the role friction plays in adding the additional spin on the first bounce, this effect is not as prevalent with balls that do not have high coefficients of friction with other surfaces. Since rubber does have a pretty high coefficient of friction with other surfaces, lacrosse balls and most bouncy balls follow this abnormal pattern, causing disaster for any ignorant owner who happens to drop it.