o In general, F1 + F2 + F3 +------ + Fn = 0
Friction o Friction is a contact force that opposes relative motion. o No friction exists till an external force is applied. There are 3 types of Friction: o
Static friction o
o
Force that resists initiation of motion of one body over another with which it is in contact
Opposes Impending motion o
Denoted by fs Let the ball be at rest initially Applied force, Fa = 0; Static friction, fs = 0