Centripetal acceleration; ball on string, lariat, rotating beam with water jars. EXAMPLE: A satellite orbiting 200 miles above the Earths surface is 4,170 miles from center of the Earth (the Earths radius is 3,970 miles). Acceleration due to gravity is 8.9 m/s2 at that altitude. What must the velocity of the satellite be for it to go around in a circular orbit? How long will it take to go around once?