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CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2000

  • question_answer
    A stationary police car sounds a siren with a frequency of 990 Hz. If the speed of sound is 330 m/s, an observer, driving towards the car with a speed of 33 m/s, will hear a frequency of:

    A)  891 Hz                 

    B)         900 Hz

    C)  1089 Hz               

    D)         1100 Hz

    E)  1210 Hz

    Correct Answer: C

    Solution :

    From Dopplers effect the perceived frequency\[f\]is given by \[f=f\left( \frac{v+{{v}_{o}}}{v} \right)\] Given, \[f=990\,Hz,v=300\,m/s,{{v}_{o}}=33\,m/s\] \[\therefore \]  \[f=990\left( \frac{330+33}{330} \right)\]                 \[=990\times \frac{363}{330}=1089\,Hz\]


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