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I INTRODUCTION TO STATICS

1 Mechanics

Mechanics is a branch of the physical sciences that is concerned
with the state of rest or motion of bodies that are subjected to the
action of forces. In general, this subject can be subdivided into three
branches: rigid-body mechanics, deformable-body mechanics, and
fluid mechanics. In this book we will study rigid-body mechanics
since it is a basic requirement for the study of the mechanics of
deformable bodies and the mechanics of fluids. Furthermore, rigid-
body mechanics is essential for the design and analysis of many types
of structural members, mechanical components, or electrical devices
encountered in engineering.
Rigid-body mechanics is divided into three areas: statics,
kinematics and dynamics. Statics deals with the equilibrium of bodies,
those that are either at rest or move with a constant velocity.
Kinematics is described the motion of bodies without reference to the
forces which either cause the motion or are generated as a result of the
motion. Whereas dynamics is concerned the relationship between the
change in motion of a body and the forces that cause this change. We
can consider statics as a special case of dynamics, in which the
acceleration is zero; however, statics deserves separate treatment in
engineering education since many objects are designed with the
intention that they remain in equilibrium.
Historical Development. The subject of statics developed very
early in history because its principles can be formulated simply from
measurements of geometry and force. For example, the writings of
Archimedes (287–212 B.C.) deal with the principle of the lever.
Studies of the pulley, inclined plane, and wrench are also recorded in
ancient writings – at times when the requirements for engineering
were limited primarily to building construction. Since the principles of
dynamics depend on an accurate measurement of time, this subject
developed much later. Galileo Galilei (1564–1642) was one of the
first major contributors to this field. His work consisted of
experiments using pendulums and falling bodies. The most significant
contributions in dynamics, however, were made by Isaac Newton
(1642–1727), who is noted for his formulation of the three

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