Topic: Simple pendulum· Oscillations and Waves

Two pendulums of length 121 cm and 100 cm start vibrating in phase. At some instant, the two are at their mean position in the same phase. The minimum number of vibrations of the shorter pendulum after which the two are again in phase at the mean pos…

Two pendulums of length 121 cm and 100 cm start vibrating in phase. At some instant, the two are at their mean position in the same phase. The minimum number of vibrations of the shorter pendulum after which the two are again in phase at the mean position is :

1. 8

2. 11

3. 9

4. 10

Doubtly Asked 30 Oct 2026 NEET UG 2022 Practice test neet Save WhatsApp Report

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Answer: 2. 11

Time period \(T\propto\sqrt l\), so \(T_{121}:T_{100}=11:10\).

They are next in phase when the shorter pendulum has made one more vibration than the longer one: \(n\cdot T_s=(n-1)T_l\).

\(10n=11(n-1)\Rightarrow n=11\).

The shorter pendulum makes 11 vibrations. Option (2).

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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Two pendulums of length 121 cm and 100 cm start vibrating in phase. At some instant, the two are at their mean position in the same phase. The minimum number of vibrations of the shorter pendulum after which the two are again in phase at the mean pos…

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