2. Solved Papers
  3. J & K CET Engineering

J & K CET Engineering J and K - CET Engineering Solved Paper-2010

  • question_answer
    A source of sound is approaching an observer with speed of \[30\text{ }m{{s}^{-1}}\]and the observer is approaching the source with a speed of\[60\,\,m{{s}^{-1}}\]. Then the fractional change in the frequency of sound (speed of sound in air \[=330\,\,m{{s}^{-1}}\]) is

    A)  \[\frac{1}{3}\]

    B)  \[\frac{3}{10}\]

    C)  \[\frac{2}{5}\]

    D)  \[\frac{2}{3}\]

    Correct Answer: B

    Solution :

    Given,    \[{{v}_{s}}=30\,m{{s}^{-1}}\] \[{{v}_{o}}=60\,m{{s}^{-1}}\] Apparent frequency \[v'=v\left[ \frac{v+{{v}_{o}}}{v-{{v}_{s}}} \right]\] \[v'=v\left[ \frac{330+60}{330-30} \right]\] \[v'=v\left[ \frac{390}{300} \right]\] \[\Rightarrow \] s\[v'=\frac{39}{30}v\] \[\therefore \]  Fractional change in frequency \[\frac{\frac{39}{30}v-v}{v}=\frac{9}{30}=\frac{3}{10}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner