The bob of a simple pendulum is hollow. If half of it is filled with water, what will be the effect on its time period?

Explanation

The centre of gravity of the hollow bob is at its centre. Thus, the distance from the point of suspension to the centre of the bob is the effective length (L) of the pendulum. When the bob is half filled with water, the centre of gravity of the bob is lowered. Thus, the effective length of the pendulum increases. Hence, the time period (T) of oscillation of the pendulum also increases as `TpropsqrtL`.