Figure 3 Rectangular Coordinate System
Vectors are symbolized in specific ways in texts and on graphs, using letters or rectangular
In Written Materials
In textbooks, vector quantities are often represented by simply using a boldfaced letter (A, B, C, R).
Particular quantities are predefined (F - force, V - velocity, and A - acceleration). Vector quantities
are sometimes represented by ,
. Regardless of the convention used, specific vector
quantities must include magnitude and direction (for example, 50 mph due north, or 50 lbf at 90 ).
Vector quantities are graphically
represented using the rectangular
coordinate system, a two-dimensional
system that uses an x-axis and a y-axis.
The x-axis is a horizonal straight line.
The y-axis is a vertical straight line,
perpendicular to the x-axis. An
example of a rectangular system is
shown in Figure 3.
The intersection of the axes is called
the point of origin. Each axis is
marked off in equal divisions in all four
directions from the point of origin. On
the horizonal axis (x), values to the
right of the origin are positive (+).
Values to the left of the origin are
negative (-). On the vertical axis (y),
values above the point of origin are
positive (+). Values below the origin are negative (-). It is very important to use the same units (divisions)
on both axes.
The rectangular coordinate system creates four infinite quadrants. Quadrant I is located above and
to the right of the origin. Quadrant II is located above and to the left of the origin. Quadrant III is
situated to the left and below the origin, and quadrant IV is located below and to the right of the
origin (see Figure 3).