Two cars A and B are moving away from each other in opposite directions. Both the cars are moving with speed of  20\:m^{-1} with respect to the ground . If an observer in car A detects a frequency 2000\:\:Hz  of the sound coming from car B , what is the natural frequency of the sound source in car B ?

 

  • Option 1)

    2250\:\:Hz

  • Option 2)

    2060\:\:Hz

  • Option 3)

    2300\:\:Hz

  • Option 4)

    2150\:\:Hz

 

Answers (1)

Frequency detected by A = 2000 Hz

 

\Rightarrow2000=f\left [ \frac{340-v}{340+v} \right ]

\Rightarrow2000=f\left [ \frac{320}{360} \right ]

\Rightarrow2000=f \times \frac{8}{9}

\Rightarrow f=2250\:Hz


Option 1)

2250\:\:Hz

Option 2)

2060\:\:Hz

Option 3)

2300\:\:Hz

Option 4)

2150\:\:Hz

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