Explain Friction Force (Ffrict)

Force exerted by a surface as an object moves across it or makes an effort to move across it. There are 2 parts of friction force - sliding and static friction. Usually the friction force often opposes the motion of an object. For instance if a book slides across the surface of a desk then the desk exerts a friction force in the opposite direction of its motion. Friction results from the two surfaces being pressed jointly closely, causing intermolecular attractive forces among molecules of dissimilar surfaces. Thus friction depends upon the nature of the two surfaces and upon the degree to which they are pressed together. The maximum amount of friction force that a surface can exert upon an object can be measured using the formula: Ffrict = µ x Fnorm