Kinetic friction

For a sliding object, the kinetic friction force fk opposes the motion. In the absence of external pushing, kinetic friction stops a moving object.

Basic feature:   fk is proportional to the normal force:  fk = μk N.

Here μk is the kinetic friction coefficient, a dimensionless number that depends only on the two surfaces in contact. Typical values are the range 0.1 - 1.0.