2 Vectors A scalar quantity is one that has nothing to do with spatial direction. Examples are length, time, mass, temperature, density, charge, and volume etc; each has a scale or size, but no associated direction. Scalars are specified by ordinary numbers, and add and subtract in the usual way. Two cups in a tray plus seven cups in another give nine cups in total. A vector quantity is one that can only be specified completely by providing both its magnitude and direction. Examples are displacement, velocity, acceleration, force, momentum etc. A vector quantity can be represented by an arrow drawn to scale. The length of the arrow indicates the magnitude of the vector and the direction of the arrow represents the direction of the vector. The resultant of a number of vectors of a particular type is that single vector that would have the same effect as all the original vectors taken together.