What keeps satellites going?
Teaching Guidance for 5-11 11-14
Wrong Track: Something must keep satellites going. Don't they have rockets which push them around their orbit?
Right Lines: Once the satellite has been accelerated into its orbit by a rocket thrust, it continues along that orbit, being tugged into its path by the gravitational pull of the Earth. In empty space the satellite would neither speed up nor slow down, but would keep travelling along its orbit forever. In low satellite orbits where there is a thin atmosphere, the air creates a drag and slows down the satellite. In such cases there is the need for occasional rocket thrusts to maintain the motion of the orbiting satellite.