MGIMS WARDHA MGIMS WARDHA Solved Paper-2013

  • question_answer
    If the radius of the earth is reduced by 1% without changing its mass. The change in g will be

    A)  2% decrease                    

    B)  2% increases

    C)  1% decrease                    

    D)  1% increases

    Correct Answer: A

    Solution :

                    From the relation of g \[g=\frac{GM}{{{R}^{2}}}\]or\[g\propto \frac{1}{{{R}^{2}}}\](at constant mass) \[\therefore \]  \[\frac{{{g}_{2}}}{{{g}_{1}}}={{\left( \frac{{{R}_{1}}}{{{R}_{2}}} \right)}^{2}}\] Where,   \[{{R}_{1}}=R\]and\[{{R}_{2}}=R-\frac{R}{100}\] \[\therefore \]  \[\frac{{{g}_{2}}}{{{g}_{1}}}={{\left( \frac{2}{R-0.1R} \right)}^{2}}={{(1-0.02)}^{2}}\] \[[{{(1+x)}^{3}}=1+nx\]where \[|x|<<|\]                 \[\frac{{{g}_{2}}-{{g}_{1}}}{{{g}_{1}}}\times 100=[(1+0.02)-1]\times 100\]=2%decreaes


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