The bob of a simple pendulum is a spherical hollow ball filled with water. A plugged hole near the bottom of the oscillating bob gets suddenly unplugged. During observation, till water is coming out, the time period of oscillation would

Options

A. first increase and then decrease to the original value
B. first decrease and then increase to the original value
C. remain unchanged
D. increase towards a saturation value

Answer

A

Explanation

The bob filled completely with water has its centre of mass at its centre. The time period of oscillation is
`T= 2pi sqrt((l)/(g))`
As the water starts coming out of the bob, its centre of mass shifts vertically downwards as a result effective length of the pendulum increases and hence its period also increases. When the bob is empty, again its centre of mass appears at its centre and as a result, the period of oscillation again reaches to its original value.