JEE Main & Advanced Physics Gravitation / गुरुत्वाकर्षण Question Bank Self Evaluation Test - Gravitation

  • question_answer
    At what height from the surface of earth the gravitational potential and the value of g are\[-5.4\times 1{{0}^{7}}J k{{g}^{-1}} and 6.0 m{{s}^{-2}}\]respectively? Take the radius of earth as 6400 km:

    A) 2600 km           

    B) 1600 km

    C) 1400 km        

    D)        2000 km

    Correct Answer: A

    Solution :

    [a] As we know, gravitational potential (v) and acceleration due to gravity (g) with height \[\operatorname{V}=\frac{-GM}{R+H}=5.4\times 1{{0}^{7}}\]             ?(i) And \[g=\frac{GM}{\left( R+H \right)}=6\]           ...(ii) Dividing (i) by (ii) \[\frac{\frac{-GM}{R+H}}{\frac{GM}{{{\left( R+H \right)}^{2}}}}=\frac{-5.4\times 1{{0}^{7}}}{6}\Rightarrow \frac{5.4\times {{10}^{7}}}{\left( \operatorname{R}+H \right)}=6\] \[\Rightarrow \operatorname{R}+h=9000km\,so,h=2600k\]


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