What is friction? Friction = force that opposes the motion of two surfaces that are touching Always happens in the direction opposite of the direction of motion

Friction - SLIDING Explanation – opposes the motion of sliding objects Labeled Picture   Explanation – opposes the motion of sliding objects Additional Example – sledding, brakes on a car, writing with pencil, moving heavy furniture

Friction - STATIC Labeled Picture   Explanation – frictional force on a non-moving object Additional Example – pushing a heavy box, skis sticking to snow when not moving

Friction - ROLLING Labeled Picture   Explanation – friction between wheels and a flat surface Additional Example – bikes, cars, trains, skateboard, furniture dolly, rolling suitcase

Friction - FLUID Labeled Picture   Explanation – force that opposes the motion of objects traveling in liquids or gases Additional Example –swimming, hand out a moving car’s window (air resistance), walking on a wet floor