JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2013

  • question_answer
    The change in the gravitational potential energy when a body of mass m is raised to a height\[nR\]above the surface of the earth is (where R is the radius of the earth)

    A)  \[\left( \frac{n}{n+1} \right)mgR\]                         

    B)  \[\left( \frac{n}{n-1} \right)mgR\]

    C)  \[nmgR\]                           

    D)  \[\left( \frac{mgR}{n} \right)\]

    Correct Answer: A

    Solution :

                    \[{{U}_{e}}=-\frac{GMm}{R}\] \[{{U}_{h}}=-\frac{GMm}{(R+nR)}=-\frac{GMm}{R(n+1)}\] Thus, magnitude of the change in gravitational potential energy                 \[\Delta U={{U}_{h}}-{{U}_{e}}\]                 \[=\frac{GMm}{R}\left( 1-\frac{1}{(n+1)} \right)\]                 \[=\left( \frac{n}{n+1} \right)\frac{GMm}{R}=\left( \frac{n}{n+1} \right)mgR\]


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