| 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. |
| F = - dU/dx = 0 | F = - dU/dx = 0 | F = - dU/dx = 0 |
d2U/dx2 = positive
i.e., rate of change of dU/dx is positive. | d2U/dx2 = negative
i.e., rate of change of dU/dx is negative. | d2U/dx2 = 0
i.e., rate of change of dU/dx 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. |
