Assertion: The condition of equilibrium for a rigid body is -
Translational equilibrium: $\sum _{}\overrightarrow{\mathit{F}}=0$, (i.e. the sum of all external forces equal to zero.)
Rotational equilibrium :$\sum _{}\overrightarrow{\tau }=0$ (i.e. the sum of all external torques equal to zero.)
Reason: A rigid body must be in equilibrium under the action of two equal and opposite forces.