Web apps for Astrophysics I at EPFL Go to the homepage. Chapter 1 : Planetary Motion The Two-Body Problem Kepler's First Law Kepler's Second Law Kepler's Third Law Chapter 2 : Tidal Forces Tidal Forces Roche Limit Tidal Locking Chapter 3 : Virial Theorem Virial Theorem Mass of a Globular Cluster N-Body Accuracy