GPS (Global Positioning Satellites) send out signals that are used by a receiver to pinpoint its position. A GPS receiver fitted into a car tells a driver exactly where the car is and which direction it's going in.
- If a Satellite's speed is too low, it will fall to the ground
- If its initial speed is too great, it will fly off into space
- At the correct speed, it orbits the Earth
The 'period' of a satellite is the time it takes to make one orbit.