The Four Types of Friction

Static Friction
when a force is applied to an object but it does not cause it to move
example: pushing on a wall
Fluid Friction
occurs when a object moves through a fluid, meaning either a liquid or gas
examples: skydiving, swimming
Sliding Friction
occurs when solid surfaces slide over each other
example:falling on the pavement
Rolling Friction
occurs when an object rolls over another (something with wheels or that is circular like a ball)
example: riding a motorcycle