1. Friction

2. Friction is: Force between two objects that are moving and touching Objective is to slow down the object (in terms of motion)

3. Types of Friction KINETIC FRICTION: Object changing motion STATIC FRICTION: Objects staying still Surface being rough or smooth will determine amount of friction.

4. Hills and Valleys The roughness of a surface determines the amount of friction  Microscopically all objects have hills and valleys  The closer your valleys and hills the smoother the surface because there is less space to slow an object down  The further apart your valleys and hills the rougher the surface because there is more space to slow an object down. rougher surface=more friction  To reduce friction, fill in valleys (oil, wax, water, etc…)  To reduce friction, wear down hills (sand, smash, etc…) Smoother surface=less friction  To increase friction, create more hills or valleys or both