Vectors are used throughout engineering and physics because their arithmetic parallels the standard ways of combining force, velocity, acceleration, and other quantities. In this video we look at some examples of each of these, and introduce some games to help you get the feel for velocity anjd acceleration in a vector framework. Then we discuss Archimedes' Principle of the Lever, and give a vector reformulation of it, which naturally leads to the definition of the center of mass of two or more objects. Barycenteric coordinates link center of mass to affine combinations of vectors.