Physics group
The Physics group controls how particles move once emitted. You can set properties such as Gravity and Turbulence and set controls for making particles bounce on other layers in the composition. The concepts are pretty advanced, but the controls are quite simple.
The full Physics group, with Air and Bounce subgroups.
Physics Model
The Physics Model determines how the particles move. There are two Models available.
Gravity
Gravity makes particles fall downwards in a natural way. The particles pick up speed as they fall, just like any object in real world would. Low values make the particles fall slowly. High values make the particles fall more quickly. The gravity value can also be set to negative values to make particles appear to float up instead of down over time.
Physics Time Factor
This control enables full control over the particle simulation rate. Time Factor can be used to speed up or slow down the particle movements, or freeze them completely, or even play their motion in reverse. This control is keyframeable to allow you to start and stop the simulation. Read more about Physics Time Factor.
Air group
The Air group has a set of modifiers that control how the particles move through air, with forces like air resistance, spin and wind controls to push and pull on the particles. This group is active when Air is chosen in Physics Model menu. Read more about this group on the Air group page.
The controls and subgroups in the Air controls group.
Bounce group
The Bounce model is used to make particles bounce on layers in the composition. This group is active when Bounce is chosen in Physics Model menu. Read more on the Bounce group page or you can read a tutorial on the Make Bounce page.
The Bounce group of controls sets the values for how particles bounce off of up to two layers.