AMU Medical AMU Solved Paper-2014

  • question_answer
    The measured value of length of a simple pendulum is 20 cm known with 2 mm accuracy. The time for 50 oscillations was measured to be 40 s with Is resolution. Calculate, the percentage accuracy in the determination of acceleration due to gravity g from the above measurements.

    A)  6.0%                                    

    B)  7.2%  

    C)  9.4%                                    

    D)  10.2%

    Correct Answer: A

    Solution :

                    We know that,                 \[g=\frac{4{{\pi }^{2}}l}{{{T}^{2}}}=4{{\pi }^{2}}l{{T}^{-2}}\] The fractional error in g is given by                 \[\frac{{{\delta }_{g}}}{g}=\frac{{{\delta }_{l}}}{l}-2\frac{{{\delta }_{T}}}{T}\](ignoring constant terms \[4{{\pi }^{2}}\]) The maximum fractional error in g is                 \[{{\left| \frac{{{\delta }_{g}}}{g} \right|}_{\max }}=\frac{{{\delta }_{l}}}{l}+2\left( \frac{{{\delta }_{T}}}{T} \right)\] The percentage error in g is \[{{\left| \frac{{{\delta }_{g}}}{g} \right|}_{\max }}\times 100=\frac{{{\delta }_{l}}}{l}\times 100+2\left( \frac{{{\delta }_{T}}}{T}\times 200 \right)\]                 \[=\frac{2}{20}\times 100+2\left( \frac{0.001}{0.50} \right)\times 100\]                 \[=2%+2\times (2%)\]                 \[=2%+4%=6.0%\]


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