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

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.