How will the period of oscillation change if the water begins to drain out of the hollow sphere?

QUESTION:

The bob of a simple pendulum is a hollow sphere filled with water. How will the period of oscillation change, if the water begins to drain out of the hollow sphere?

ANSWER:

When water begins to drain out of the hollow sphere (simple pendulum bob), the center of mass of the system will first move down and then will come up to the Center of the hollow sphere i.e. initial position. Due to this the equivalent length of the simple pendulum( l ) increases hence time period(T) first increases, reaches to a maximum value and then decreases till it becomes equal to its initial value.