1. Notes: Friction Static friction (F s ) is the force that opposes initial motion between two contacting surfaces. (standing friction) When a force is applied to an object (F applied ) and the force of static friction (F s ) opposes it equally, the object does not move. -F app Fs NO MOTION It is in equilibrium.

2. Static friction (F s ) The greatest value of an applied force (F applied ), before an object starts moving, is F s,max. When is F s,max overcome, the object will move in the direction of the applied force F applied. Fs-F app

3. Kinetic friction (F k ) is the force that reduces motion between two moving objects, in contact. (sliding friction) The value of kinetic friction is less than static friction F k < F s -FkFapplied The total force (F net ) acting on an object is the difference between the applied force (F applied ) and the force of kinetic friction (F k ). F net = F applied - F k

4. Calculating Friction Friction is directly related to the normal force and the type of surface an object is in contact with Coefficients of friction  Kinetic =  k = F k = kinetic friction F N normal force Static =  s = F s,max = static friction max F N normal force Frictional force F f =  F N = coefficient of friction x normal force

5. Kinetic or static? Why? Define what all the arrows mean

6. Kinetic or static? State why and what all the arrows mean