Coefficient of Restitution of a Golf Ball

COEFFICIENT OF RESTITUTION The coefficient of restitution (e or COR) is defined as a number that serves as an index of elasticity for colliding bodies (Hall, 2012). Essentially, it measures the rebound of a ball after a collision with another object, like a golf club striking a stationary golf ball. A perfectly elastic ball will have a COR of 1, and a perfectly plastic ball will have a COR of 0. In golf, the coefficient of restitution comes into play when the club head impacts the ball, and has a direct effect on how far the ball will travel after impact. Once the club head strikes the ball, the ball is deformed and flattened by the impact and the transfer of energy. Different brands of balls are made from different materials, and some balls have harder cores, while others have softer cores. The strength of the core directly relates to the coefficient of restitution; with a harder core, the ball will deform less and travel farther because of a more efficient transfer of kinetic energy from club to ball. With a softer core, too much energy will be spent deforming the ball and it will not travel as far. Here is the equation for the coefficient of restitution. e = √ hb / hd
Coefficient of restitution= the square root of the height of the bounce divided by the height of the drop.

For this project we measured the COR of a Titlelist 4 golf ball. We dropped the ball from a height of 1.24m five times to get a consistent height of the bounce. The results of the bounces were all around .914m high. Here is a sample problem for the coefficient of restitution of a Titlelist 4 golf ball: e = √ (.914 m / 1.24 m) = .86
With the results of this experiment we were able to conclude that a Titlelist 4 golf ball has a coefficient of restitution of .86. That number shows that this brand of golf balls will bounce pretty high and is more elastic than it is plastic. This means that when the club head impacts the ball, the kinetic energy will efficiently transfer

References: Hall, S. J. (2012). Basic biomechanics (6th ed). New York: McGraw-Hill.