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trough the centroid or geometric center of this area, /2b from the
support.

Fig. 1-6.

Forces distinguish by a method location in space:
Concurrent Force System. Since a concurrent force system is
one in which the lines of action of all the forces intersect at a common
point O;
Coplanar Force System. In the case of a coplanar (or two-
dimention) force system, the lines of action of all the forces lie in the
same plane;
Three-dimention Force System. In the case, the lines of action
of all the forces lie arbitrary in the space.
Parallel Force System. The parallel force consists of forces that
are all parallel to any axis.

4 Free-Body Diagrams

Successful solution of Statics problems requires a complete
specification of all the known and unknown external forces that act on
the body. The best way to account for these forces is to draw a free-
body diagram. This diagram is a sketch of the outlined shape of the
body, which represents it as being isolated or “free” from its
surroundings, i.e., a “free body.” On this sketch it is necessary to show
all the forces and couple moments that the surroundings exert on the
body so that these effects can be accounted for when the equations of
equilibrium are applied. A thorough understanding of how to draw a

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