ABSTRACT
This chapter deals with the fundamental principles which states that some physical quantity is either conserved or balanced. Every material body, as well as every portion of such a body is endowed with a non-negative, scalar measure, called the mass of the body or of the portion under consideration. The law ofconservation of mass asserts that the total mass of any portion of a continuum medium remains unchanged during the motion, that is, remains constant in every configuration. The principle of balance of angular momentum states that the time rate of change of total angular momentum of any portion of a nonpolar continuum about any fixed point is equal to the resultant moment about the same point of the external forces acting on this portion. Thermodynamics is a study primarily centered around the principles of energy and entropy and their various applications.
