The coefficient of friction is a dimensionless scalar value, which is a ratio of the force that exists between two objects and another force pushing them together. The coefficient of friction can be broken down into two types of measurements;
- The coefficient of static friction; determined from a ratio of the maximum static force (F) between the surfaces before any movements occurs to the normal (N) force.
- The dynamic/kinetic coefficient of friction; is determined from the ratio of the kinetic force (F) between the surfaces while one surface is moving across the other to the normal force Ff/N.
Both these entities are depended on the surfaces involved. These values are determined experimentally using a Zwick Roell ZwickiLine Z5.0 TN for Flexible Low-Force Testing machine, following international standards ASTM 1894 and ISO 8295.