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CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2008

  • question_answer
    A bus is moving with a velocity of 5 ms towards a huge wall. The driver sounds a horn of frequency 165 Hz. If the speed of sound in air is\[335\text{ }m{{s}^{-1}},\] the number of beats heard per second by a passenger inside the bus will be

    A)  3                            

    B)         4                            

    C)  5                            

    D)         6

    E)  7

    Correct Answer: C

    Solution :

    \[f=f\left( \frac{v-{{v}_{L}}}{v-{{v}_{s}}} \right)\] \[=165\left( \frac{335+5}{335-5} \right)\]\[(\because {{v}_{L}}=-5m{{s}^{-1}},{{v}_{s}}=5m{{s}^{-1}})\] \[=165\times \frac{340}{330}\] \[=170\text{ }Hz\] Therefore, the number of beats heard \[=170-165=5\]


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