1. Friction What is friction?

2. Answer Me!!! Think of two factors that affect friction.

3. Friction Friction is the force that opposes relative motion of two objects in contact. Block Surface Block Surface

4. Coefficient of Friction The frictional interaction between two surfaces is measured with the coefficient of friction. The bigger the coefficient of friction, the “stickier” the two surfaces will be together.

5. Types of Friction Static Friction is the force that opposes the start of motion. Kinetic Friction is the force that opposes two that are in motion. kinetic friction < static friction

6. Normal Force The Normal Force (F N ) is the force pressing two objects together. On a horizontal surface, F N = -F G F G = mg F N = -mg

7. Force of Friction Where F f is the Force of Friction F N is the Normal Force And  is the coefficient of friction

8. Final Thought… A 2kg rubber block is being dragged across a horizontal ice rink at a constant velocity. Calculate the force of friction acting on the block.

9. Answer Me!!! How will the weight of a crate affect the frictional force acting on that crate?

10. Answer Me!!! A 10 N wooden crate is being dragged across a horizontal wooden surface at a constant speed of 4 m/s. How much force is being used to pull the box?

11. Friction on an Incline If an object is on an inclined surface, the normal force (F N ) is equal to the component of F G that is perpendicular to the surface. FNFN FGFG F G_|_

12. Constant Velocity When an object moves at a constant velocity:  Acceleration = 0 m/s 2  Net Force = 0 N  Force Pulling = Force Resisting

13. Answer Me!!! A 12 N block slides down a 20 o incline at a constant speed. What is the coefficient of friction between the block and the incline?