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Physics · Simple Harmonic Motion

JEE Main 2026 — 23 January, Morning Shift — Question 31

A simple pendulum of string length 30 cm performs 20 oscillations in 10s. The length of the string required for the pendulum to perform 40 oscillations in the same time duration is ____\_\_\_\_ cm. [Assume that the mass of the pendulum remains same.]

  1. Option A:

    120

  2. Option B:

    0.75

  3. Option C:

    7.5

    Correct
  4. Option D:

    15

Answer: C

Step-by-step solution

Time period becomes half and T∝ℓ\mathrm{T} \propto \sqrt{\ell} So, length ℓ\ell beocmes ℓ4\frac{\ell}{4}

So, ℓ4=304=7.5\frac{\ell}{4}=\frac{30}{4}=7.5

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Paper
23 January, Morning Shift
Subject
Physics
Chapter
Simple Harmonic Motion
Topic
Simple Pendulum and Angular SHM