A rocket is fired vertically with a speed of `5 km s^-1` from the earth’s surface. How far from the earth does the rocket go before returning to the earth ? Mass of the earth = `6.0 xx 10^24 kg`, mean radius of the earth = `6.4 xx 10^6 m`, G = `6.67 xx 10^-11 N m^2kg^-2`.