ABSTRACT
This chapter looks at the general concept of central forces and their importance in describing physical phenomena. It examines the problem of two objects interacting via a central force, this is the so called two-body problem. Our analysis of the two-body problem will lead to Kepler's laws of planetary motion. The chapter then aims to examine the specific case of a planet orbiting a star. A central force is a force on a particle that is directed along a line that joins the particle and the force center. The chapter looks at the general problem of determining the orbits of a particle with a reduced mass moving in a central force field. Kepler's original statement was that the planet's period squared was proportional to the cube of its semimajor axis. The chapter aims to examine the circular restricted three-body problem which is a relatively simple formulation of the three-body problem. However, even the circular restricted three-body problem must be analyzed numerically.
