1. The force of gravity is attractive. Why does the Moon then follow a circular path rather than just falling into the Earth?
2. Satellites orbiting the Earth will eventually crash to Earth unless their orbits are corrected. What force would cause a satellite to lose altitude and eventually crash into the Earth? (Hint: what effect does the Earth's atmosphere have on the satellite?)
3. Summarize briefly how the following properties of planets
can be measured. In your summary, be sure to identify any other quantities
that must first be measured.
(a) distance
(b) mass
(c) radius of orbit
(d) radius of planet
Last updated April 7, 2008