By possessing an understanding of Newton's Laws, following these three laws
of

graphical solutions, and understanding vector algebra you can solve
most

engineering static problems. Systems of Force Systems of force acting on
objects

in equilibrium can be classified as either concurrent or
nonconcurrent and as

either coplanar or noncoplanar. This gives us four
general categories of

systems. The first category, concurrent-coplanar forces
occur when the lines of

action of all forces lie in the same plane and pass
through a common point.

Figure 1 illustrates a concurrent-coplanar force
in such that F1, F2, and W all

lie in the same plane (the paper) and all
their lines of action have point O in

common. To determine the resultant of
concurrent force systems, you can use the

Pythagorean theorem, the law of
sines, or the law of cosines as outlined in the

previous chapter.
Nonconcurrent-coplanar force is when the lines of action of

all forces lie in
the same plane but do not pass through a common point as

illustrated in
figure 2. The magnitude and direction of the resultant force can

be
determined by the rectangular component method using the first two
equations

in figure 2, and the perpendicular distance of the line of action
of R from the

axis of rotation of the body can be found using the third
equation in figure 2.

Concurrent-noncoplanar forces are when Application
the lines of action of all

forces pass through a common point and are not in
the same plane. To find the

resultant of these forces it is best to resolve
each force into components along

three axes that make angles of 90 degrees
with each other.

Nonconcurrent-noncoplanar forces are when the lines of
action of all forces do

not pass through a common point and the forces do not
all lie in the same plane.

Stress When a restrained body is subject to
external forces, there is a tendency

for the shape of the body.