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 $g = 9.8 \;ms^{–2}$, then the orbital speed of the satellite is :

Question

( A ) $6.67 \; km\;s^{-1}$
( B ) $7.76 \; km\;s^{-1}$
( C ) $8.56 \; km\;s^{-1}$
( D ) $9.13 \; km\;s^{-1}$