The coefficient of restitution entered the common vocabulary, among golfers at least, when golf club manufacturers began making thin-faced drivers with a so-called "trampoline effect" that creates drives of a greater distance as a result of an extra bounce off the clubface. The USGA (America's governing golfing body) has started testing drivers for COR and has placed the upper limit at 0.83, golf balls typically have a COR of about 0.78. According to one article (addressing COR in tennis racquets), "[f]or the Benchmark Conditions, the coefficient of restitution used is 0.85 for all racquets, eliminating the variables of string tension and frame stiffness which could add or subtract from the coefficient of restitution.”
The International Table Tennis Federation specifies that the ball must have a coefficient of restitution of 0.94.
A rubber ball
When a rubber ball collides with an immobile flat surface (like massive marble floor), the object will rebound with some fraction of its original energy. If the collision is perfectly elastic, then the ball will rebound with all of the energy it arrived with and its rebound velocity will be the same as its approach velocity. In this case, the coefficient of restitution is said to