ABSTRACT
Magnitudes alone are enough to describe quantities such as length, area, volume, time, temperature, and speed. Such quantities are called scalars, because a simple scale can indicate their values. Other quantities, in contrast, are slightly more complex in that they involve not only magnitude but also direction. Examples are force (including weight), velocity, and acceleration. (The force of gravity acts downward; the automobile's speed is 50 kilometers per hour but its velocity is 50 kilometers per hour in a specified direction; and so on.) These more comprehensive quantities are called vectors.
