2.7 Kinetic and Static Friction

Kinetic Friction

Kinetic friction occurs when two surfaces slide past one another. It opposes the direction of motion and depends on the roughness of the surfaces in contact. The magnitude of kinetic friction is given by:

${F_{f,k} = \mu_k F_N}$

${F_{f,k}}$ is the kinetic frictional force

${\mu_k}$ is the coefficient of kinetic friction

${F_N}$ is the normal force

Kinetic friction is independent of contact area and speed (for most cases) but depends strongly on the materials of the surfaces.