Mechanics

Abstract

Engineering mechanics is the study of forces and their effects on the objects to which they are applied. This chapter presents the fundamentals of the study of mechanics in the two categories of static mechanics, (or simply statics) and dynamic mechanics. The first section deals with statics and addresses stationary objects. Statics is based on a reduction of Newton's second law (F  =  ma) and the equivalent equation describing rotational motion for the special case where the accelerations are zero. This results in the equations of equilibrium, which state that the vector sum of all forces and moments acting on a static body must be zero. Equations of static equilibrium can be used to find, for example, forces generated by supports that constrain a body against externally applied loads. Principles of statics are also used to understand the internal forces in the material comprising a structure under load. Understanding these forces is fundamental to the design of structures to avoid material failure. The second section is devoted to dynamic mechanics which is concerned with the motion of bodies. It is divided into two parts, kinematics and dynamics (also called kinetics). Kinematics is the study of motion without consideration of the forces and moments that produce the motion. Relationships between displacement, velocity, and acceleration are part of the study of kinematics. Dynamics relates the motion of bodies to the action of applied forces and moments, and thus is fundamental to many engineering problems.