JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2007

  • question_answer
        A satellite of mass m revolves around the earth of radius R at a height\[x\]from its surface. If g is the acceleration due to gravity on the surface of the earth, the orbital speed of the satellite is

    A)  \[gx\]                                  

    B)  \[\frac{gR}{R-x}\]

    C)  \[\frac{g{{R}^{2}}}{R+x}\]                           

    D)  \[{{\left( \frac{g{{R}^{2}}}{R+x} \right)}^{1/2}}\]

    Correct Answer: D

    Solution :

                    The gravitational force exerted on satellite at a height\[x\]is \[{{F}_{G}}=\frac{G{{M}_{e}}m}{{{(R+x)}^{2}}}\] where\[Mg=\]mass of earth Since, gravitational force provides the necessary centripetal force, so,                 \[\frac{G{{M}_{e}}m}{{{(R+x)}^{2}}}=\frac{mv_{o}^{2}}{(R+x)}\] where\[{{v}_{o}}\]is orbital speed of satellite, \[\Rightarrow \]               \[\frac{G{{M}_{e}}m}{(R+x)}=mv_{o}^{2}\] \[\Rightarrow \]               \[\frac{g{{R}^{2}}m}{(R+x)}=mv_{o}^{2}\]                 \[\left( \because g=\frac{G{{M}_{e}}}{{{R}^{2}}} \right)\] \[\Rightarrow \]               \[{{v}_{o}}=\sqrt{\left[ \frac{g{{R}^{2}}}{(R+x)} \right]}={{\left[ \frac{g{{R}^{2}}}{(R+x)} \right]}^{1/2}}\]


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