Question

A simple pendulum has a bob which is a hollow sphere full of sand and oscillates with certain period. If all that sand is drained out through a hole at its bottom, then its period

(a) Increase 

(b) Decreases 

(c) Remains same

(d) Is zero

Answer 1

During the draining of the sand the period first increases due to change in effective length, then decreases and finally attains a value that it had when the sphere was full of sand.