Statics (source code)
= Statics
<Statics> studies mechanical <equilibrium>: configurations in which the relevant <forces> and <torques> balance. For a <rigid body> at rest in an <inertial frame>, the conditions are $\sum\mathbf F=0$ and $\sum\boldsymbol\tau_O=0$, with all <torques> calculated about the same point $O$.
A horizontal beam carrying a downward load illustrates why both equations are necessary. Vertical <force> balance fixes the sum of the support reactions, while <torque> balance determines how the load is divided between supports. Equilibrium alone does not imply <dynamical stability>: a perfectly upright <inverted pendulum> satisfies force and torque balance but falls after a sufficiently small disturbance.
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