AMU Medical AMU Solved Paper-1998

  • question_answer
    The ratio of the angular momenta associated with the earths rotation about its own axis and earths orbital motion is (radius of earth\[=6\times {{10}^{6}}\]m and mean earth-sun distance\[=1.5\times {{10}^{11}}m\])

    A)  \[2.5\times {{10}^{-7}}:1\]     

    B)  \[1:2.5\times {{10}^{-4}}\]

    C)  \[1:1\]             

    D)  \[4\times {{10}^{-5}}:1\]

    Correct Answer: A

    Solution :

    : Angular momentum about own axis\[{{J}_{A}}=I\omega \] \[\therefore \]\[JA=\frac{2}{5}M{{R}^{2}}\times \frac{2\pi }{T}\]where\[T=1\]day or \[{{J}_{A}}=\frac{2}{5}M{{R}^{2}}\times \frac{2\pi }{1}\]                 ................ (i) Angular momentum of earth in its orbit around sun. \[{{J}_{0}}=M{{r}^{2}}{{\omega }_{1}}\] or \[{{J}_{0}}=M{{r}^{2}}\times \frac{2\pi }{365}\] \[\therefore \] \[\frac{{{J}_{A}}}{{{J}_{0}}}=\frac{2}{5}M{{r}^{2}}\times 2\pi \times \frac{360}{M{{r}^{2}}\times 2\pi }\] \[=\frac{2\times 365}{5}{{\left( \frac{R}{r} \right)}^{2}}=146\times {{\left( \frac{6\times {{10}^{6}}}{1.5\times {{10}^{11}}} \right)}^{2}}\] \[=2.336\times {{10}^{-7}}\]or \[\frac{{{J}_{A}}}{{{J}_{0}}}\approx \frac{2.5\times {{10}^{-7}}}{1}\]


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