Question

the bob of a simple pendulum is a ball full of water . if a fine hole is made in the bottom of the ball ,what will be its effect on the time period of the pendulum

Answer 1

when a hole is made in the of a sphere full of water,the water flows out slowly through the hole. As the water flows out of the sphere, the centre of mass of the system will first move down and then will come up.
Due to this the equivalent length of pendulum L and hence time period T first increase, reaches a maximum value and then decreases till it decreases till it becomes equal to its initial value.