## 6.2    Properties of Friction

Experiments show that friction has 3 properties:

1.      If the body does not move, then the static frictional force equals the applied force.

2.      The magnitude of  has its maximum value fs,max that is related to the magnitude of the normal force  of the body on the surface:  , ms is the coefficient of static friction for the two surfaces that are in contact.

 force slider

 Script by Dr. Mohamed S. Kariapper using Physlets from

3.      When the applied force  exceeds fs,max, the body begins to slide. We have accelerated motion toward the left as seen in the above figure. When sliding the magnitude of the frictional force rapidly decreases to a value fk given by .  is the force of kinetic friction and mk is the coefficient of kinetic friction. ms and mk are property of the two surfaces that are in contact.

Demos/Animations Examples/Checkpoints Interactive Problems
am = animation ,dm = demo, cp = checkpoint, ex = example, ip = interactive problem