Circular motion problems deal with concepts like gravity and centripetal force. Whether it is a moon orbiting around a planet where gravity provides the centripetal force, or a weight on a string swung in a circle, where tension provides the centripetal force, you can find out all you want to know about the motion of these objects with just a few simple equations.
     Scientists at NASA use the laws of circular motion to calculate a trajectory when launching space missions. Civil engineers use circular motion equations when designing highways to make sure that cars traveling at a certain speed limit will be able to travel safely, and not skid off the road if a curve is too sudden.

Planetary Reference
      Planetary problems often involve many different physical constants and statistics about the planets and moons. It is always a hassle to look up these numbers to ensure accuracy. I have gathered all of the planetary data that we could find, and placed it in a convenient table form.  
Updated 7/20/99

Equivalence of Conservation of Angular Momentum and Conservation of Energy Methods for Satellite Velocity Calculations

      In teaching Introductory College or University Physics to undergraduates or advanced high school students, problems involving elliptical orbits are frequently presented with the objective of enriching the students' understanding of orbital mechanics. An exercise nearly always encountered in these first-year classes consists of relating the velocity of a satellite (whose mass is treated as being insignificant compared to that of the central body) at its apoapsis to the velocity of the satellite at its periapsis. Some students will choose to solve the problem using conservation of angular momentum, while others will use conservation of energy relationships.
     The teacher is able to assure the students that the relationships are equivalent (both physical laws must hold), though it is by no means obvious that this is so by inspection alone.
Updated 8/9/99