University of Virginia
Uva Physics: Using Vectors to Describe Motion
Background information on vectors and their use in describing motion in two dimensions. A comparison of Aristotle's and Galileo's perspectives on force and motion is given.
Wolfram Research
Wolfram Math World: Math World: Vector Addition
Defines vector addition and gives the algebraic notation for adding vectors. Includes a graphic and links to additional information.
National Council of Teachers of Mathematics
The Math Forum: Vector Addition: Geometry
Illustrates and describes how to add two vectors graphically.
Walter Fendt
Walter Fendt: Resultant of Forces (Addition of Vectors)
A short interactive activity which allows you to visualize the sum of vectors.