Force and acceleration are both vectors; they have direction as well as magnitude. Newton’s second law shows that acceleration and force are proportional, which means that an object’s acceleration—but not necessarily its velocity—is in the direction of the net force. Applying this idea to 2-dimensional motion resolves many seeming puzzles of the physical world. This lecture explores applications of Newton’s laws in multidimensional motion and explores the common forces, including normal forces, tension forces, and friction.