Chapter 11, Problem 40A

To determine

To identify: The balancing act that is in stable equilibrium, unstable equilibrium or nearly neutral equilibrium.

Explanation of Solution

Introduction:

Stability of the body can be defined in terms of the equilibrium. When the sum of the all forces acting on the body is said to be balanced, then body is in equilibrium. There are three types of equilibrium.

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

When body is said to be in the stable equilibrium, displacement of the body is in the opposite direction to that the applied force exerts on it. Centre of gravity of the system is in the lowest position. Sum of the forces acting on the body is zero. In unstable equilibrium when body displaces from its position, direction of the displacement is in the direction of the applied force. Centre of gravity in this case in the highest position. While in case of neutral equilibrium displacement of the body is independent of its initial position.

Consider the first case as shown below.

A figure represents the man who is clinging on the rope. Its center of gravity is on the wire. Its displacement is not depending on the initial position. In this case body is in the neutral equilibrium.

Consider the second case as shown below.

In this case man is walking on the rope with monkey sitting on his head. In this case center of gravity of the system of man along with monkey is above the rope which is the point of support. In this case system is in unstable equilibrium.

Consider the third case as shown below.

In this case man is ridding the bicycle and two girls hanging below the rope. The center of gravity in this case is in the lowest position as compared to the above cases. In this case system is in the stable equilibrium.