Q.23 Two identical solid balls, one of ivory and the other of wet clay, are dropped from the same height on the floor. Which one will rise to a greater height after striking the floor and why?

Hint: The height of the bounce will depend on the modulus of elasticity. 
Since, ivory ball is more elastic than wet clay ball, therefore, ivory tries to regain its original shape quickly. Hence, more energy and momentum is transferred to the ivory ball in comparison to the wet clay ball and therefore, ivory ball rises higher after striking the floor.