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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Sound Waves

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Sound Waves

A piston is inserted into a cylindrical tube of small cross section...

A piston is inserted into a cylindrical tube of small cross section whose other end is open. The tube resonates with a tuning fork having a frequency of 512 Hz512 \text{ Hz}. As the piston is gradually pulled out of the tube, a second resonance is observed when the piston has been displaced by a distance of 32.0 cm32.0 \text{ cm}. Determine the speed of sound in the air inside the tube.

Options

  1. A340 m/s340 \text{ m/s}
  2. B164 m/s164 \text{ m/s}
  3. C655 m/s655 \text{ m/s}
  4. D328 m/s328 \text{ m/s}

Correct answer

D. 328 m/s328 \text{ m/s}

Step-by-step solution

The distance between two consecutive resonant lengths in a closed organ pipe is equal to half the wavelength of the sound wave.

ΔL=λ2\Delta L = \dfrac{\lambda}{2}

Given that the displacement of the piston between the first and second resonance is 32.0 cm32.0 \text{ cm}, we have:

ΔL=32.0 cm=0.32 m\Delta L = 32.0 \text{ cm} = 0.32 \text{ m}

λ2=0.32⇒λ=0.64 m\dfrac{\lambda}{2} = 0.32 \Rightarrow \lambda = 0.64 \text{ m}

The speed of sound vv is given by the relation:

v=fλv = f \lambda

Substituting the given frequency f=512 Hzf = 512 \text{ Hz} and the calculated wavelength λ=0.64 m\lambda = 0.64 \text{ m}:

v=512×0.64=327.68 m/sv = 512 \times 0.64 = 327.68 \text{ m/s}

Rounding off to the nearest integer, we get v≈328 m/sv \approx 328 \text{ m/s}.
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