I animate 4 type of bouncing balls by observing the difference of the ball's physical property and its weight. I also analyze how does it affect:

The timing and travel distance of each bounce (Contact pose to Contact pose)
The overall timing that determines the number of bounces.
The height of each Up pose when it bounces.

These animated bouncing ball includes 

a) Soccer ball
b) Ping Pong ball
c) Bowling ball
d) Squash and Stretch Soccer ball