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JEE Main 2017 (9 Apr, Shift 1) · Wave Basics & Properties of Sound

Wave Basics & Properties of Sound question from JEE Main 2017 (9 Apr, Shift 1)

Q31JEE Main 2017 · 9 APR · SHIFT 1Medium

Wave Basics & Properties of Sound

In an experiment to determine the period of a simple pendulum of length 1 m, it is attached to different spherical bobs of radii r1 and r2. The two spherical bobs have uniform mass distribution. If the relative difference in the periods, is found to be 5×10−4 s, the difference in radii, ∣\vert r1 −- r2 ∣\vert is best given by:

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Answer: (b)

  1. Effective length ≈L+r\approx L + r, so T=2π(L+r)/gT = 2\pi\sqrt{(L+r)/g} and ΔTT=12ΔrL\dfrac{\Delta T}{T} = \dfrac{1}{2}\dfrac{\Delta r}{L}.
  2. Δr=2LΔTT=2×1×5×10−4=10−3 m\Delta r = 2L\dfrac{\Delta T}{T} = 2 \times 1 \times 5\times10^{-4} = 10^{-3}\ \text{m}
  3. So the answer is (b) 0.1 cm0.1\ \text{cm}.
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