1. 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

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

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

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

5. Friction - FLUID
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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