Draw a graph to show the variation of frictional force with applied force.

${\mu }_{s } and {\mu }_{k }$ are the coefficient of static friction and kinetic friction.
If applied force(F) is less than  ${\mu }_{ } N$ then friction force will be equal to applied force .
If applied force(F) is equal to ${\mu }_{ } N$ then friction force is known as limiting friction force.
If applied force(F) is beyond ${\mu }_{ } N$ then friction force decrease to kinetic friction(${\mu }_{k}N$)