A hollow sphere is filled with water . It is hung by a long thread . As the water flows out of a hole at the bottom , the period of oscillation will

Explanation

`T=2pisqrt((1)/(g))`
(i) As the water flows out of the sphere, the time period first increases and then decreases,
(ii) Initially when the sphere is completely filled with water ,its C.G lies at its center.
(iii) As water flows out, the C.G being to shift below the centre of the sphere the effective length of the pendulum increases & hence its time period increase when the sphere becomes more than half empty , its C.G beings to rise up the effective length of the pendulum increases and true period T decreases.
(iv) when the entire water is drained out of the sphere , the C.G is once again shifted to centre of the sphere and the time period T aatains its initial value.