• # question_answer A remote-sensing satellite of earth revolves in a circular orbit at a height of $0.25\times {{10}^{6}}\,m$above the surface of earth. If earth's radius is $6.38\times {{10}^{6}}\,m$and $g=9.8\,m{{s}^{-2}},$then the orbital speed of the satellite is A) $6.67\,km\,{{s}^{-1}}$B) $7.76\,km\,{{s}^{-1}}$C) $8.56\,km\,{{s}^{-1}}$D) $9.13\,km\,{{s}^{-1}}$

For the satellite revolving around earth ${{v}_{0}}=\sqrt{\frac{G{{M}_{e}}}{({{R}_{e}}th)}}=\sqrt{\frac{G{{M}_{e}}}{{{R}_{e}}\left( 1+\frac{h}{{{R}_{e}}} \right)}}=\sqrt{\frac{g{{R}_{e}}}{1+\frac{h}{{{R}_{e}}}}}$ Substituting the values ${{v}_{0}}=\sqrt{60\times {{10}^{6}}}\,m/s$ ${{v}_{0}}=7.76\times {{10}^{3}}\,m/s=7.76\,km/s$