A curling stone of mass 20 kg and initially traveling at 2.0 m/s
collides head-on with a lighter stone of mass 15 kg which is
initially at rest. After the collision the struck stone has a speed
of 1.6 m/s in the same direction as the initial velocity of the
heavy stone. a) What is the final velocity of the heavy stone? b)
Is this collision elastic? Explain. If the collision is not
elastic, find the macroscopic energy lost in the collision