Composition and resolution of forces, velocities, etc

A force is a vector quantity – it has magnitude and direction, and can be rep­resented by a straight line, passing through the point at which the force is applied, its length representing the magnitude of the force, and its direction corresponding to that in which the force is acting. Forces can be added, or sub­tracted, to form a resultant force, or they can be resolved, that is to say, split into component parts, by drawing the vectors to represent them (Fig. 1.9).

Fig 1.9 Composition and resolution of vector quantities

Note that velocity and momentum are also vector quantities and can be rep­resented in the same way by straight lines. Mass, on the other hand, is not; a mass has no direction, and this is yet another distinction between a force and a mass.