Question

how to calculate Kinetic and static coefficient of friction

Answer 1

Kinetic friction, also known as sliding friction or moving friction, is the amount of retarding force between two objects that are moving relative to each other. This is important in understanding the coefficient of kinetic friction, which is the proportion you get when you take the pulling force needed to keep an object moving and divide that by the force holding the two sliding surfaces together. This coefficient is specific to the materials involved in the contacting surfaces. A rougher surface will have a higher coefficient.

The equation that helps you to find the coefficient of kinetic friction is this:

Coefficient of Kinetic Friction

The normal force is the amount of force perpendicular to the surfaces that are in contact, or the force holding the objects together. And the force of kinetic friction is the amount of force necessary to keep the two objects moving relative to each other. The force of kinetic friction acts in a opposite direction to the movement of the two objects.

For an object at rest on a flat surface, with no other force acting on it, the normal force would be the force of gravity on the object, or the weight of the object. This force is calculated by multiplying the object's mass by the acceleration of gravity (N=mg). Two cubes lying next to each other on a flat surface with faces touching would have a normal force of zero because there is no force holding the two surfaces together.

Answer 2

The force of static friction can be calculated by taking the coefficient offriction between the two surfaces and multiplying it by the normal force that the surface is applying to the object. On a flat surface, the normal force is equal to the force of gravity acting down on the object.