Principles of Animation
In the example below a normal ball won’t have much of squash and stretch as compared to a rubber ball because the weight and materials are different. Similarly, in the case of a metal ball; there won’t be any stretch and squash as the ball is very heavy and it falls without any squash. Thus, squash and stretch also help in defining the material of the object by its visual appearance.
Also, there are forces that apply to the object. In the below example, the ball doesn’t bounce by itself but there are forces that act upon the ball. Like Gravity that pulls the ball down and as the ball is stopped abruptly by a surface it squashes. Speed also plays an important role as the ball catches speed since gravity pulls it down. The ball tends to stretch in the direction it is going.
Kindly refer to the videos for detailed process:
Exercise:
For practicing stretch and squash it’s better to try animating a bouncing ball and apply the principle to understand how stretch and squash work.