Pixilation - Frame-by-Frame Stop Motion: The Guide to Non-Traditional Animation Techniques - page 35

stop turning, the car continues slightly forward with secondary motion and
the chassis settles back to its default position directly over the tires. Once this
principle is understood, the director or actor can break these rules and create
some different effects.
Secondary motion basically means that any appendage or secondary mass like
hair on a head or a tail of an animal trails behind the main body of movement.
For example, if a person quickly turns his or her head, the hair trails a few
frames behind the mass of the head, which is the source of the movement.
The head stops, but the hair continues around past the head's stationary
position then settles down.
Fig 3.4 Secondary motion of hair as it trails behind the turn of a head.
Anticipation basically means that, to move in a particular direction, you must
first move slightly in the opposite direction. This wind-up builds energy and
allows the audience to see what is about to happen for a beat before it actually
happens. This is exaggerated in animation but often does happen in real life.
Fig 3.5 the wind-up or anticipation allows an audience time to focus on an object before it
moves, and anticipation builds energy just before that action occurs.