The friction coefficient is defined as the ratio of the frictional force to the ______ acting on an object.

The friction coefficient is defined as the ratio of the frictional force to the normal force acting on an object. The normal force is the perpendicular force that the surface exerts on the object, balancing its weight or any other perpendicular forces. By dividing the frictional force by this normal force, we obtain a dimensionless number that tells us how much friction exists for a given surface pair. For example, if a 10‑newton block slides across a floor and the friction force is 3 newtons, the coefficient of friction is 3 ÷ 10 = 0. 3, meaning the friction is 30 % of the normal force.