1. Friction Acts in direction of plane (i.e. up or down the table) Factors affecting friction Limiting friction F lim =  R

2. Factors Affecting Friction Mass of object Material of surface & object Area of contact Shape of contact Other forces (& others…)

3. Limiting Friction The amount of force required to overcome friction There is a limit to the amount of friction between an object and a surface Friction, or limiting friction, is largely dependent on mass of object F lim =  R Amount of force required to overcome friction Coefficient of friction (all the other factors) Normal reaction force (  mg) 0 ≤  ≤ 1

4. More on friction Friction is in direction opposite to motion (it opposes the force) At point of movement the friction is ‘limiting’ (and in direction opposite to motion) At point of movement F =  R Friction is always ≤  R (in case above friction is equal to  R)