In physics, dynamics is a branch of classical mechanics, that is concerned with the effect of forces on the motion of objects or bodies. The incorporation of forces distinguishes dynamics from kinematics, while motion distinguishes it from statics. Dynamics is normally subdivided into kinematics, forces, and deformation.
Kinematics (Greek: kinein, to move) describes the motion of objects without the consideration of the forces that bring about the motion. In kinematics the position of a body is represented as a function of time. The position is represented with a set of coordinates in a reference frame. Velocity is the rate of change of position. Acceleration is the rate of change of velocity. Velocity and acceleration are the two principal quantities in kinematics which describe how position changes.
The forces encountered in this book are constrained to surface and body forces. A convenient representation of the forces are stresses (i.e., force per unit area), and a mathematical representation of the internal forces in a continuum is provided in the section 2.3.1 Coordinate stresses. The generic Cauchy equations of motion, valid for both solids and fluid, are presented in the section 2.4 Cauchy's equations of motion. A separate the chapter 3 Deformation is devoted to deformation analysis. And further, separate chapters (4 Elasticity,5 Fluid mechanics) are devoted to constitutive equations which relate stresses to deformation. A constitutive equation is a relation between stress and strains (often represented by tensors), specific to a material or body, and does not follow directly from a physical law. By substitution of the constitutive equation into the Cauchy equations, the dynamics of the material may be solved when appropriate boundary conditions are imposed.