BHU PMT BHU PMT (Screening) Solved Paper-2005

  • question_answer
    If the length of a pendulum is made 9 times and mass of the bob is made 4 times, then the value of time period becomes:

    A)  3T                                         

    B)  3/2T

    C)  4T                                         

    D)  2T

    Correct Answer: A

    Solution :

                     The periodic-time of a simple pendulum is given by \[T=2\pi \sqrt{\frac{l}{g}}\] where\[l\]is length of pendulum, g is acceleration due to gravity. Given, \[{{T}_{1}}=T,{{l}_{1}}=l,{{l}_{2}}=9l\] \[\therefore \]  \[\frac{{{T}_{1}}}{{{T}_{2}}}=\sqrt{\frac{{{l}_{1}}}{{{l}_{2}}}}=\sqrt{\frac{1}{9}}=\frac{1}{3}\] \[\Rightarrow \]               \[{{T}_{2}}=3{{T}_{1}}=3T\] Note: The periodic-time of the pendulum does not depend upon the mass of the bob.


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