•A force is applied to a body
resting on a surface but it does not move yet; a friction
force of the same magnitude but opposite in direction keeps
the body from moving – static frictional forcefs.
•As the applied force is
increased, fsreaches its
maximum beyond which it cannot increase; the body starts to
move as the applied force becomes greater than the
friction.The friction that is now present (a constant value) is
called the kinetic frictional force, fk.