A satellite is revolving around the earth in a circular orbit of radius 8000km.with what speed this satellite is projected in the orbit?

18.    A satellite is revolving around the earth in a circular orbit of radius 8000 km. With what speed this satellite be  projected in the orbit ? What will be its period of revolution ? (g = 9.8 m $s^{-2}$, radius of the earth 6400 km). 
                                                                                  Ans.   7.08 km $s^{-1}$, 118 minutes.