Static friction

Determining the Coefficient of Friction.

Friction is a resistive force that prevents two objects from sliding freely against each other. The coefficient of friction (μ) is a dimensionless number, the ratio of the resistive force of friction (F_r) and by the normal or perpendicular force (F_n) pushing the objects together. It is represented by the equation:
μ = F_r / F_n.

It must be noted that friction is proportional to the normal force, rather than the actual weight of the mass in contact;it is invariant to the surface area in contact (only at macroscale).

There are different types and values for the coefficient of friction, depending on the type of resistive force. The coefficient of friction can be determined through experiments, such as measuring the force required to overcome friction or measuring the angle at which an object will start to slide off an incline.