Page 3 - mechanics

Chapter – 1 Introduction

(3) Strength of materials expands statics to include material
properties and also pays more attention to distributed forces.
Generally, for engineering students, statics and dynamics will
be discussed in level 000 while, Strength of materials will be
discussed in level 100.

1.2 Cartesian Co-ordinate System
In mechanics problems, we need to describe the position of

objects and where forces act. This needs to be done relative to
the same reference. A basic concept in mechanics is the
coordinate system. We begin by defining the basic and simplest
one known as Cartesian (rectangular) coordinate system.

In one dimensional case, where forces and motion are on a
straight line, this line is the coordinate axis of such a problem.
A reference point is chosen as the zero of the number scale and
a direction is set as the positive direction as in Figure (1.1).
Points have only one coordinate to describe its position.

Negative Positive
Half Half

-3 -2 -1 0 1 2 3

Fig. 1.1 One dimensional coordinate system.
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