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JEE Main 2020 (2 Sep, Shift 2) · Stationary Waves & Vibrating Strings

Stationary Waves & Vibrating Strings question from JEE Main 2020 (2 Sep, Shift 2)

Q85JEE Main 2020 · 2 SEP · SHIFT 2Medium

Stationary Waves & Vibrating Strings

A wire of density 9 ×\times 10–3 kg cm–3 is stretched between two clamps 1 m apart. The resulting strain in the wire is 4.9 ×\times 10–4. The lowest frequency of the transverse vibrations in the wire is: (Young’s modulus of wire Y = 9 ×\times 1010 Nm–2), (to the nearest integer), _________

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

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Answer: 35

  1. ρ=9×10−3 kg/cm3=9×103 kg/m3\rho = 9\times10^{-3}\text{ kg/cm}^3 = 9\times10^{3}\text{ kg/m}^3
  2. Stress =Y×strain=9×1010×4.9×10−4=4.41×107 N/m2= Y \times \text{strain} = 9\times10^{10}\times4.9\times10^{-4} = 4.41\times10^{7}\text{ N/m}^2
  3. v=stressρ=4.41×1079×103=70 m/sv = \sqrt{\dfrac{\text{stress}}{\rho}} = \sqrt{\dfrac{4.41\times10^7}{9\times10^3}} = 70\text{ m/s}
  4. n=v2L=702=35 Hzn = \dfrac{v}{2L} = \dfrac{70}{2} = 35\text{ Hz}
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