VIT Engineering VIT Engineering Solved Paper-2009

  • question_answer
    A clock pendulum made of invar has a period of 0.5 s, at \[20{}^\circ C\]. If the clock is used in a climate where the temperature averages to\[30{}^\circ C\], how much time does the clock lose in each oscillation? \[(\text{For invar},\alpha =9\times {{10}^{-7}}{{/}^{0}}C,\,g=cons\tan t)\]

    A)  \[2.25\times {{10}^{-6}}s~\]

    B)  \[2.5\times {{10}^{-7}}s\]

    C)  \[5\times {{10}^{-7}}s~\]

    D)  \[1.125\times {{10}^{-6}}s\]  

    Correct Answer: A

    Solution :

    Time period of oscillation,     \[T=2\pi \sqrt{\frac{l}{g}}\] \[\Rightarrow \] \[\frac{dT}{T}=\frac{1}{2}\frac{dl}{l}\]            As, \[\frac{dl}{l}=\alpha dt\] \[\Rightarrow \]           \[\frac{dT}{T}=\frac{1}{2}\alpha dt\] \[=\frac{1}{2}\times 9\times {{10}^{-7}}\times (30-20)\] \[=4.5\times {{10}^{-6}}\] \[\therefore \]Loss in time \[=4.5\times {{10}^{-6}}\times 0.5\] \[=2.25\times {{10}^{-6}}s\]


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