A rubber ball filled with water, having a small hole is used as the bob of a simple pendulum. The time period of such a pendulum (a) is a constant. (b) decreases with time. (c) increases with time. (d) first increases and then decreases, finally having same value as at the beginning.

Answer: (d). Effective length is up to the centre of mass of the bob; T ∝ √(l). As water drains, the centre of mass first goes down ( T increases), then returns to the centre when empty ( T decreases back). So the answer is (d) first increases and then decreases, finally having same value as at the beginning.

A rubber ball filled with water, having a small hole is used as the… | MHT CET 2023 (9 May, Shift 1)

Q41MHT CET 2023 · 9 MAY · SHIFT 1Easy

Simple Pendulum

A rubber ball filled with water, having a small hole is used as the bob of a simple pendulum. The time period of such a pendulum

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Answer: (d)

Effective length is up to the centre of mass of the bob; $T \propto \sqrt{l}$ .
As water drains, the centre of mass first goes down ( $T$ increases), then returns to the centre when empty ( $T$ decreases back).
So the answer is (d) first increases and then decreases, finally having same value as at the beginning.

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