Stable

Unstable

Neutral

When a particle is displaced slightly from a position, then a force acting on it brings it back to the initial position, it is said to be in stable equilibrium position.

When a particle is displaced slightly from a position, then a force acting on it tries to displace the particle further away from the equilibrium position, it is said to be in unstable equilibrium.

When a particle is slightly displaced from a position then it does not experience any force acting on it and continues to be in equilibrium in the displaced position, it is said to be in neutral equilibrium.

Potential energy is minimum.

Potential energy is maximum.

Potential energy is constant.

i.e. rate of change of  is positive.

i.e. rate of change of   is negative.

i.e. rate of change of is zero.

Example :

A marble placed at the bottom of a hemispherical bowl.

Example :

A marble balanced on top of a hemispherical bowl.

Example :

A marble placed on horizontal table.