Julius Sumner Miller 55 HHOF - Coefficient of Restitution

Professor Julius Sumner Miller describes the coefficient of restitution with an example using a steel ball dropped onto a flat steel surface. The coefficient of restitution is based on Newton's Law of Restitution which deals with collisions. This law states that the speed of two bodies after collision is dependent on the material from which they are made. Initially, the measurement of the nature of the material(s) colliding was called the Coefficient of Restitution. But, because the coefficient of restitution is a unit-less ratio, this means there can be several ways to calculate this ratio depending on the type of data collected. The coefficient of restitution can be based on the ratio between the final and the initial speed of two bodies before and after a colliding. The coefficient of restitution can be based on the ratio of kinetic energy of two bodies before and after colliding, and there are still other data measurements that could be used. Professor Julius Sumner Miller shows us how to calculate the coefficient of restitution based on the ratio between the height the ball was dropped and the height the ball bounced after "colliding" with the steel surface.