Gravity, Newton and Orbits: Practice Problem Solutions

1. An orbit is a continuous fall around a planet: the object falls toward the planet but also moves sideways so fast that the surface curves away beneath it.

2. Speed decreases and period increases.

3. They and the station are falling together (free fall), so nothing pushes them against the floor. Gravity there is still about 89% of surface gravity.

4. About 11.2 km/s.

5. It orbits in 24 hours, matching Earth's spin, so it hangs over the same spot; good for weather and communications.

6. About 17 pounds (one-sixth).

7. Using a planet's gravity and motion to speed up or change direction a spacecraft, saving fuel.