CBSE Class 11-science Answered

Equilibriums can be classified as (a) stable equilibrium, (b) metastable equilibrium, and (c) unstable equilibrium;

These equilibriums can be illustrated using analogy examples in the mechanical equilibrium of a ball shown above in figure.

The ball in Fig. (a) is in stable equilibrium because it can always return to equilibrium after displacement.

In this case potential energy is minimum

The ball in Fig. (c) is in unstable equilibrium because equilibrium cannot be maintained after any displacement.

Potential energy is greater than that of case(a)

The ball in Fig. (b) is in metastable equilibrium because it can return to equilibrium after small displacement.

If the displacement is large, the ball will move to a new equilibrium position. Potential energy is greater than case(a)

but lower than case (c)