1. FRICTION

2. Friction A force that acts in a direction opposite to the motion Will cause a moving object to slow down and finally stop

3. Source of Friction Friction occurs because the surface of any object is rough. Even surfaces that appear smooth cause friction.

4. Rougher Surfaces The rougher the surface, the greater the friction. Example: Pavement is much rougher than grass, more friction is produced when you slide on the pavement than on grass.

5. Mass and Friction Objects with more mass need more force to overcome friction, objects with less mass need less force to overcome friction.

6. Types of Friction Sliding Friction- occurs when two solid surfaces slide over each other. Example: When you go sledding, or apply the brakes on a bicycle or car.

7. Types of Friction Rolling Friction- occurs when an object rolls across a surface. Makes objects easier to move than with sliding friction. Example: Anything with wheels uses rolling friction.

8. Types of Friction Fluid Friction – occurs when a solid object moves through a fluid. Fluids include liquids and gases. Example: The friction between air and a fast moving car is the largest force opposing the motion of the car.

9. Static Friction Static Friction is when a force is applied to the object but the object does not move. Static friction disappears as soon as the object moves.