ABSTRACT
Forces are ideally represented by vectors lying along specific lines of action. If a force is a push or a pull, then the effect of a force depends upon how hard the push or pull is, the place of the push or pull, and the direction of the push or pull. Biosystems, as with most mechanical systems, are generally subjected to a number of forces applied simultaneously. There are three special force systems which are useful in the study of mechanical systems and particularly biosystems. These are: zero systems, couples, and equivalent systems. For nonrigid bodies, however, equivalent force systems can have vastly different physical effects. In the study of the mechanics of deformable materials it is convenient to superpose, or add force systems.
