Posted by help! on .
Suppose that highspeed stroboscopic photographs show that the 200g head of a golf club travels at 51 m/s just before it strikes a 50g golf ball initially at rest on a tee.
If the club head slows to at 36 m/s (in the same direction) after the collision,
what is the speed of the golf ball just after impact, and
what fraction of the original kinetic energy of the club head was lost to thermal energy? Assume that the mass of the club is concentrated mostly in the head.

Physics 
drwls,
The loss of momentum by the clud head equals the momentum acquired by the gold ball. Use that and its mass to derive the speed of the golf ball.
Then add up the kinetic energies before the collision (club head only) and afterwards (club head plus ball). Divide the before/after difference by the initial club head KE to get the fractional energy loss.