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JEE Main 2022 (28 Jul, Shift 2) · Periodic Motion & SHM Basics

Periodic Motion & SHM Basics question from JEE Main 2022 (28 Jul, Shift 2)

Q41JEE Main 2022 · 28 JUL · SHIFT 2Medium

Periodic Motion & SHM Basics

The potential energy of a particle of mass 4 kg4\text{ kg} in motion along the x-axis is given by U=4(1−cos⁡4x)U = 4(1 - \cos 4x) J. The time period of the particle for small oscillation (sin⁡θ≃θ)(\sin\theta \simeq \theta) is (πK) s\left(\frac{\pi}{K}\right)\text{ s}. The value of KK is _________.

Numerical answer type. Work it out, then open the answer.

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Answer: 2

  1. For small xx: 1−cos⁡4x≈(4x)22=8x21 - \cos 4x \approx \frac{(4x)^2}{2} = 8x^2, so U≈32x2U \approx 32x^2.
  2. Compare with U=12kx2U = \frac{1}{2}kx^2: k=64 N/mk = 64\text{ N/m}.
  3. ω=km=644=4 rad/s\omega = \sqrt{\frac{k}{m}} = \sqrt{\frac{64}{4}} = 4\text{ rad/s}, T=2π4=π2 sT = \frac{2\pi}{4} = \frac{\pi}{2}\text{ s}
  4. So K=2K = 2.
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