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The bob of a simple pendulum is a spherical hollow ball filled with water. A plugged hole near the bottom of the oscillating bob gets suddenly unplugged. During observation, till water is coming out, the time period of oscillation would
- first decrease and then increase to the original value
- first increase and then decrease to the original value
- increase towards a saturation value
- remain unchanged
Correct answer: first increase and then decrease to the original value
Solution
As water drains, the centre of mass of the water (and hence the effective pendulum length) first lowers then rises back to the centre, so the period first increases and then decreases to its original value.
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