Abstract

We postulate the basic principle of dynamics and derive the second equation of the fluid model, the equation of motion. The dynamics of the fluid is investigated. We introduce the notion of momentum of the body, study the rate of change of momentum and discuss forces acting on a body. The body forces and the contact forces and corresponding densities are considered. The equation of motion in the Cauchy form is obtained. Finally, we propose the simplest form of the stress tensor which gives the equation of motion of the perfect fluid.