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JEE Main & Advanced JEE Main Paper (Held On 9 April 2017)

  • question_answer
    In an experiment to determine the period of a simple pendulum of length 1m, it is attached to different spherical bobs of radii \[{{r}_{1}}\] and \[{{r}_{2}}\]. The two spherical bobs have uniform mass distribution. If the relative difference in the periods, is found to be \[5\times {{10}^{-4}}s,\] the difference in radii, \[|{{r}_{1}}-{{r}_{2}}|\] is best given by - [JEE Online 09-04-2017]

    A)  0.01 cm                               

    B)  0.1 cm

    C)  0.5 cm                 

    D)  1 cm

    Correct Answer: B

    Solution :

      \[T\propto \sqrt{l}\]                     \[l=1\] \[\frac{\Delta T}{l}\,=\frac{1}{2}\,\,\frac{\Delta l}{l}\,\,\,\,\,\,\,\,\,\,\,\,\,\Delta l={{r}_{1}}-{{r}_{2}}\] \[5\times {{10}^{-4}}\,=\frac{1}{2}\,\frac{{{r}_{1}}-{{r}_{2}}}{1}\] \[{{r}_{1}}-{{r}_{2}}\,=10\times {{10}^{-4}}\] \[{{10}^{-3}}\,m={{10}^{-1}}\,cm\,=0.1\,cm\]


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