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RAJASTHAN ­ PET Rajasthan PET Solved Paper-2005

  • question_answer
    A tuning forks gives 5 beats/s with 20 cm length of sonometer. If length of wire changes from 20 to 21, and not change in frequency, then frequency of tuning forks will be

    A)  205 Hz          

    B)  210 Hz

    C)  220 Hz          

    D)  195 Hz

    Correct Answer: A

    Solution :

     Suppose the frequency of tuning fork is n, the frequency of wire will be\[n+5\] According to law of length \[{{n}_{1}}{{l}_{1}}={{n}_{2}}{{l}_{2}}\] Or \[(n+5)\times 20=(n-5)\times 2l\] \[20n+100=21n+105\] \[n=205Hz\]


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