At this site you will find am online discussion about the centroid of a triangle. The page begins with a discussion of observations leading to the centroid of a triangle. Dr. Math explains the correct findings as well as the errors made...

This site from NASA helps in explaining a barycenter. "In the case of the Earth and the Sun, both bodies actually revolve, or spin, around the center of the mass between them. This point is called the barycenter."

Includes exhaustive information and a wealth of activities pertaining to aerodynamics and the physics of flight.

This video segment explains centripetal force and illustrates how roller coasters rely on it to give you a thrilling ride. Includes background reading material and discussion questions. [4:40]

A page describing rotational equilibrium and non-equilibrium situations. Includes graphics, equations, and many examples.