Anything is Animated
As you go along, you will discover that the subtle manipulation of this principal will be a vital life giving property to your work. This principal is also directly related to the weight of anything that is animated. A skilled animator can make a simple circle outline appear to have the properties of the heaviest bowling ball or the lightest soap bubble depending on how it is treated with timing.
The bouncing ball exercise is often thought of as the most simple and effective way of developing a sense of timing (like in an by an infographic company): the ball slows down at the highest point of the bounce due to gravity and speeds up as it descends for the next bounce. With this exercise, you can gain a real appreciation of how the physics of motion relate to the principles of slowing in and slowing out, as well as the squashing and stretching of an object.