CHAPTER 2 - General Equations and Theorems of Motion of a Continuous Medium

Abstract

This chapter discusses the general equations and theorems of motion of a continuous medium. The chapter reviews the distribution of mass in a continuous medium. In engineering, specific weight is often used instead of density; it is defined as the limit of the ratio of the weight of a small volume to the size of the volume. The density of a moving fluid depends on the temperature, the pressure, and the nature of the motion of the medium. The density of water, as that of other capillary liquids, is only slightly dependent on temperature and is almost independent of pressure as, even under considerable pressure, the volume of the liquid changes comparatively little. On the other hand, the density of gases depends strongly on temperature and pressure. The continuity equation and the momentum-stress equations form a system of dynamical equations that describe the relation between changes of density and velocity on the one hand, and the surface and body forces applied to a liquid or gas on the other hand.