Concurrent Forces  
A.
FORCES AND STATICS
Force Concurrent Forces Colinear Forces Unit Gizmos
B. SECTION PROPERTIES
C. TRUSS ANALYSIS
D. BEAM ANALYSIS

In
a concurrent force system, all forces pass through a common point. In the
previous case involving the application of two forces to a body, it was
necessary for them to be colinear, opposite in direction, and equal in
magnitude for the body to be in equilibrium. If three forces are applied
to a body, as shown in the figure, they must pass through a common point
(O), or else the condition, SM_{o}
= 0, will not be satisfied and the body will rotate because of unbalanced
moment. Moreover, the magnitudes of the forces must be such that
the force equilibrium equations,
SF_{x} = 0, SF_{y}= 0, are satisfied. Therefore,
not only do three nonparallel forces applied to a body have to be concurrent
for the body to be in an equilibrium state, but their magnitudes and directions
must be such that the force equilibrium conditions are satisfied (SF_{x}
= SF_{y}
= 0). Notice that there is no need for the moment equilibrium equation
in this case since it is automatically satisfied.
