"Before beginning the design analysis of any product, structure or even a model of a structure, it is essential to throughly understand several basic concepts in mechanics and the behavior of materials. The first two principal subject areas in mechanics of materials are Statics and Strength of Materials. In this chapter, we introduce several of the basic concepts and physical laws included in these two subjects. These concepts and laws provide a foundation upon which the design analysis of structures such as bridges is based. We also briefly describe the history of mechanics to give you a sense of the age of the principles used in analyzing modern structural components." p2-1

EXTERNAL
COMING FROM OUTSIDE THE SYSTEM UNDER STUDY. IN MANY PROBLEMS, IT IS IMPORTANT TO KEEP TRACK OF RESOURCES OR FACTORS INSIDE AND OUTSIDE A SYSTEM BOUNDARY.

EXTERNAL FORCES

FORCE
A PUSH OR A PULL

FORCE

FREE BODY DIAGRAM
A DRAWING OF THE OBJECT UNDER STUDY, SHOWING ONLY THE OBJECT AND ALL FORCES APPLIED TO THE OBJECT.

INTERNAL
WITHIN A SYSTEM

INTERNAL FORCES
FORCES THAT ARE EXERTED BETWEEN PARTS OF THE SYSTEM

STATICS

STATICS

FPS