An artificial satellite moving round the Earth in a circular orbit possesses an acceleration which is “constant” in magnitude but “changing in direction”. An artificial satellite revolves round the earth under centripetal acceleration. By the launch rocket, immediately before the satellite is established in the predetermined orbit, the speed given to it is 30, 000 km/hr. The speed must be great enough so gravity doesn’t bring the satellite back to Earth, but not so great that the satellite escapes gravity out into space. This means that the speed, which is provided by the rocket is the source of the centrifugal force, and the attraction of the earth holds it from moving away from this centrifugal force.