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NEET Sample Paper NEET Sample Test Paper-92

  • question_answer
    A man is watching two trains, one leaving and the other coming with equal speed of 4 m/s. If they sound their whistles each of frequency 240 Hz, the number of beats heard by man (velocity of sound in air = 320 m/s) will be equal to

    A) 12                    

    B)        0   

    C) 3                     

    D)        6

    Correct Answer: D

    Solution :

    [d] The apparent frquency of sound of both the trains will be changed. The apparent frequency of sound of train coming in\[=240\times \frac{320}{320-4}\] \[=\frac{240\times 320}{316}=243\] For apparent frequency of train going away \[=240\times \frac{320}{320+4}=237\] When these sounds are heard simultaneously beat is listened. No. of beats per sec \[=243-237=6.\]


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