JCECE Medical JCECE Medical Solved Paper-2013

  • question_answer
    A clock which keeps correct time at \[20{{\,}^{o}}C,\] is subjected to \[40{{\,}^{o}}C.\]If coefficient of lineal expansion, of the pendulum is \[12\times {{10}^{-6}}/{{\,}^{o}}C,\]then how much will it gain or loss in time?

    A)  5s/day            

    B)  10.3s/day

    C)  20.6 s/day          

    D)  20 min/day

    Correct Answer: B

    Solution :

     As, \[{{T}_{2}}={{T}_{1}}\sqrt{{{l}_{2}}/{{l}_{1}}}\] \[={{T}_{1}}\times \sqrt{\frac{{{l}_{1}}[\{1+12\times {{10}^{-6}}\times (40-20)\}]}{{{l}_{1}}}}\]\[={{T}_{1}}\sqrt{1+240\times {{10}^{-6}}}\] \[\therefore \] \[\frac{{{T}_{2}}-{{T}_{1}}}{{{T}_{1}}}={{(1+240\times {{10}^{-6}})}^{1/2}}-1\] \[=120\times {{10}^{-6}}\] or \[{{T}_{2}}-{{T}_{1}}=120\times {{10}^{-6}}\times (24\times 60\times 60)s\] \[=10.36\,s/day\] It will be a loss as \[{{T}_{2}}>{{T}_{1}}.\]


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