## staticsThe branch of mechanics that deals with forces acting on bodies that are motionless. We can combine forces much as we do velocities. If forces P_{1} and P_{2}
with resultant R, act at a point, there must be a third
force, P_{3}, equal and opposite to R,
for equilibrium. We can combine forces similarly over more complex structures.
For a bridge whose weight (w) acts as a downward force W
at the center, the upward reactions R_{1} and R_{2}
at the piers must be such that R_{1} + R_{2}
= - W for it to be in equilibrium.
Similarly, we examine the members of the bridge to determine the stresses
acting on each. ## Related category• CLASSICAL MECHANICS | |||||

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