Coefficient of Restitution

 The coefficient of bounciness or restitution of an object is the fractional value representing the ratio of velocities before and after an impact. An object with a COR of 1 collides elastically, while an object with a COR < 1 collides inelastically.

For a COR = 0, the object effectively "stops" at the surface with which it collides, not bouncing at all. The coefficient of restitution is the measure of elasticity of the collision in between ball and racquet. Elasticity is the measure of bounce, or in other words, how much of the kinetic energy of the colliding objects before collision remains as kinetic energy of the objects after the collision. With an inelastic collision, some kinetic energy is changed into deformation of the material, sound, heat, and other forms of energy, and is thus unavailable for use in moving.

A perfectly elastic collision has a coefficient of restitution of 1. A perfectly plastic, or inelastic, collision has c = 0. 2 lumps of clay that do not bounce at all, but stick together. So the coefficient of restitution will always be in between zero and one.

A bouncing ball captured with the stroboscopic flash at 25 images per second. Ignoring air resistance, square root of ratio of the height of 1 bounce to that of the preceding bounce gives the coefficient of restitution for the impact of ball/surface. The coefficient of restitution is the ratio of speeds of the falling object, from when it hits the given surface to when it leaves the surface. In laymen's terms, coefficient of restitution is a measure of the bounciness. A ball is a round or spherical object which is used mostly in sports and games. Balls are made from different materials, but leather, rubber, and synthetics are common in modern times.