Use when motion needs to feel physically grounded—objects falling, characters jumping, things colliding, or any element that should obey believable weight and momentum.
Think like a physicist watching the world move. Every object has mass. Every motion has cause and consequence.
Before animating anything, ask: What does this weigh?
A feather and a bowling ball both fall, but they tell completely different stories. Your job is to make the audience feel that weight without thinking about it.
Squash & Stretch — Mass is conserved. When something compresses, it must bulge. A bouncing ball flattens on impact because its volume has to go somewhere.
Timing — Heavy = slow to start, slow to stop. Light = quick reactions. A truck and a bicycle brake very differently.
Slow In & Slow Out — Nothing starts or stops instantly. Acceleration and deceleration are the fingerprints of mass.
Arcs — Gravity curves everything. Even a punch follows a pendulum path from the shoulder. Straight lines feel robotic.
Secondary Action — When the main mass moves, attached masses follow with delay. Hair, clothing, jowls—they're all passengers on the physics train.
Follow Through & Overlapping Action — Different masses have different momentum. A character stops, but their belly keeps going. This is inertia made visible.
Anticipation — Force requires windup. You can't push without first pulling back. Show the gathering of energy before release.
Exaggeration — Push physics past reality to feel more real. A heavy landing needs more squash than actual physics would produce.
Staging — Position elements so physical relationships read clearly. The audience must understand spatial cause and effect.
Straight Ahead & Pose to Pose — Use straight ahead for chaotic physics (explosions, water). Use pose to pose for controlled physics (a character lifting something).
Solid Drawing — Volume must remain consistent. A character can't lose mass between frames without the audience noticing something is wrong.
Appeal — Even physics follows design. Decide if your world has cartoon physics or realistic physics, then be consistent.
When something feels "floaty" or "weightless":
When something feels "stiff":
Audiences don't analyze physics—they feel it. Your job isn't accuracy; it's believability. Sometimes breaking physics (hanging in mid-air before a fall) creates more convincing weight than obeying it.