States of Equilibrium

States of Equilibrium

There are three states of equilibrium of a body. They are

(i) stable equilibrium,

(ii) unstable equilibrium,

(iii) neutral equilibrium.

(i) Stable Equilibrium

A body is said to be in stable equilibrium if it comes back to its original position when it is slightly displaced. For example, a cone standing on its base. The centre of gravity of the cone is nearer the base. When this cone is displaced, its centre of gravity is raised. A cone in stable equilibrium should have its centre of gravity as low as possible. The vertical line through its centre of gravity should be within its base when the cone is disturbed. If the vertical line through the centre of gravity is within the base, a torque due to weight of the cone brings back it to the original position.

(ii) Unstable Equilibrium

A body is said to be in unstable equilibrium, if it does not come back to its original position when it is slightly displaced. A cone balanced on its apex is in unstable equilibrium. When this come is disturbed,

its centre of gravity is lowered. The vertical line through its centre of gravity is outside the base. The torque due to weight of the cone toppled the cone down. So the cone does not regain its original position.

(iii) Neutral Equilibrium

A body is said to be in neutral equilibrium if on being slightly displaced, it does not come back to its original position but occupies a new position similar to its original position. The centre of gravity of the body remains at the same height. A cone resting on its side, is in natural equilibrium. If the cone is pushed slightly, its centre of gravity is neither raised nor lowered but it remains at the same height.