Before beginning this module,

• The Student should be familiar with forces, particularly the gravitational force due to masses at the Earth's surface. (for review on forces, go to one of the sites on our forces list)
• The Student should know how to draw a "free-body diagram", indicating what forces act on an object, where they act, and in what direction. (for review on free-body diagrams, click here )
• The Student should be familiar with the concept of a cross product, including how to find its direction. (for review on vectors, go to one of the sites on our vector list)