1. Warm Up A 15 kg block sits on a frictionless slide which has an angle of incline of 30 degrees. A) Draw a Free Body Diagram of the situation B) What is the acceleration of the block down the ramp?

2. Pg 101 (Q21; P36, 37, 43, 52a)

3. Friction Force that opposes the motion of an object (prevents slippage where two objects touch)‏

4. Static Friction Friction preventing an object from moving. F fr = μ s * F N μ s Is the coefficient of static friction. Object is in equilibrium there is NO MOVEMENT

5. Example A puppy playing tug of war is being pulled by a 50 N force. If the mass of the puppy is 5 kg, and he isn’t moving, what is the coefficient of static friction between the puppy’s paws and the ground?

6. Practice A rhino playing tug of war is being pulled by a force. If the mass of the rhino is 400 kg, and he isn’t moving, the coefficient of static friction between the rhino and the ground is 0.2, what is the force pulling the rhino (if it isn’t moving)?

7. Kinetic Friction Friction that impedes the motion of a sliding object while it is moving What does ‘impedes mean’? F fr = μ k * F N μ k Is the coefficient of kinetic friction. When velocity is constant, the force pushing/pulling is equal to the force of friction.

8. Example A box is pushed across a table which has a coefficient of kinetic friction of 0.15. If the box weighs 45 N, and is moving at a constant velocity, what is the magnitude of the force pushing it?

9. Practice A crate is pushed with constant velocity across a floor. The floor and the crate have a coefficient of kinetic friction of 0.25. If the force pushing the crate is 200N, how much does the crate weigh?

10. Pg 101 (P36 and P 37)

11. Homework Worksheet