Question

A golf club with 65J of kinetic energy strikes a stationary golf ball with a mass of 46g. The energy transfer is only 20% efficient. Calculate the initial speed of the golf ball

Answer 1

Kinetic energy of golf club = 65J, 
kinetic energy supplied to golf ball = 20% of 65 = 0.2 * 65 = 13J,
kinetic energy of ball = [mass * Velocity²]/2,
mass = 46gm = 0.046Kg,
[0.046 * V²]/2 = 13, or 0.046 *V² = 26, 
V² = 26/0.046 = 565.22, 
V = 23.77 m/sec = initial velocity of golf ball after hitting.