Question 9: What type of equilibrium is guaranteed by each condition of equilibrium?

Each of the two conditions of equilibrium is necessary but not sufficient for the complete equilibrium of a body. Separately, they can only assure a part of the equilibrium.

• When the first condition of equilibrium is satisfied, i-e, , this guarantees only that there is no net force acting on the body and the body is in translational equilibrium only. In the above figure, the first condition of equilibrium is satisfied. The wooden rod has no translational acceleration. But the second condition is not satisfied. The body will rotate in clockwise direction.

• When the second condition of equilibrium is satisfied, i-e, the net torque is zero , this guarantees only that there is no net torque acting on the body and the body is in rotational equilibrium only. In the above figure, the second condition of equilibrium is satisfied. Torques in both directions are equal. However, there is a net force, 2F, acting on the body and the body will not be in equilibrium.

Therefore, for a body to be in a state of complete equilibrium, both the conditions of equilibrium must be satisfied.