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Wave Motion and Waves on a String — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsWave Motion and Waves on a String3 Marks
Question
A 2 in long string fixed at both ends is set into vibrations in its first overtone. The wave speed on the string is 200m/s and thee amplitude is 0.5cm.
  1. Find the wavelength and the frequency.
  2. Write the equation giving the displacement of different points as a function of time. Choose the X-axis along the string with the origin at one end and t = 0 at the instant when the point x = 50cm has reached its maximum displacement.
✓

Answer


$\text{V}=200\text{m/s},\ 2\text{A}=0.5\text{m}$

  1. The string is vibrating in its 1st overtone

$\Rightarrow\lambda=1=2\text{m}$

$\Rightarrow\text{f}=\frac{\text{v}}{\lambda}=100\text{Hz}$

  1. The stationary wave equation is given by

$\text{y}=2\text{A}\cos\frac{2\pi\text{x}}{\lambda}\sin\frac{2\pi\text{Vt}}{\lambda}$

$=(0.5\text{cm})\cos\big[(\pi\text{m}^{-1})\text{x}\big]\sin\big[(200\pi\text{s}^{-1})\text{t}\big]$

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