The equilibrium representation of a body by means of a figure of a block resting on a plane surface is very familiar to us since it is recurrent in the textbooks of fundamental physics. Nevertheless, in most of the cases where the frictional force is present, this representation, in general, requires greater strictness. Under this consideration, the normal force to the surface is displaced sideways, leaving the same line action of the weight force, and this fact is almost always neglect in the textbooks of fundamental physics. In this paper we will analyze the equilibrium conditions of a body in the presence of frictional forces and we will discuss the lateral displacement of the normal force to the support surface of a body.
equilibrium; frictional; displacement
