When you swing a ball on a rope in a circle above your head, what keeps it moving in that circular path? This applies to any object moving in a circle, not just a ball on a rope - the force and ...

Polar orbits take the satellites over the Earth's poles. The satellites travel very close to the Earth (as low as 200 km above sea level), so they must travel at very high speeds (nearly 8,000 m/s).