 Velocity, however, is a directed quantity, because it codifies not just the speed \(v\) with which the object moves, but also its direction. Velocity is formally represented by a vector \(\mathbf{v}\), the magnitude of which is the speed of the object \(v\), which we sometimes also call the “velocity” of the object while allowing the context to indicate that this is elliptical for “the magnitude of the velocity.” Momentum is therefore also a directed quantity, represented formally by a vector \(\mathbf{p}\). To paraphrase Taylor and Wheeler (1992, p. 191), the direction of momentum matters: A glancing blow is never as damaging as one that is head on. By analogy with velocity, the magnitude of the momentum is represented by the letter \(p\). 