Question

State the different types of equilibrium.

Answer 1

Equilibrium:

A body is said to be in equilibrium if it does not experience a change in its rest or uniform motion, even under the influence of external forces.

Types of equilibrium:

1. Stable equilibrium
2. Unstable equilibrium
3. Neutral equilibrium

Stable equilibrium:

1. A body is said to be in stable equilibrium if it regains its original position on the removal of the external force after being slightly disturbed by it.
2. A body is said to be in stable equilibrium, if the line joining the centre of gravity and the centre of earth must fall within the base of the body, after being lightly disturbed by it.

Example:

1. A cone resting on its base.
2. A book lying on a flat surface.

Diagram:

From the figure, it is clear that the line joining the centre of gravity and the centre of earth falls within the base of the body, even after being lightly disturbed by it. So the cone is in stable equilibrium.

Unstable equilibrium:

1. A body is said to be in unstable equilibrium if it does not regains its original position after being slightly disturbed by an external force.
2. Here the line joining the centre of gravity and the centre of earth falls outside its base, after being lightly disturbed by an external force.

Example:

1. A cone resting on its apex.
2. A bottle standing on the edge of its mouth.

Diagram:

Here the base of the body is small and the top portion is heavier as it raises the height of the centre of gravity from its base.

Neutral equilibrium:

A body is said to be in neutral equilibrium when it moves to a new place on the application of an external force and on the removal of the external force the body may or may not come back to its original place, but the height of its centre of gravity from a reference surface remains the same.

Example:

1. A rolling ball.
2. A cone resting on its side.

Diagram:

1. In neutral equilibrium the line joining the centre of gravity and the centre of earth falls within the base of the body on the application of an external force.
2. The height of its centre of gravity does not change even after the application of an external force.