Stability of a System

A system is a certain region on which we concentrate our attention. When we talk about the stability of a system, it is with respect to a particular attribute. A system may be stable with respect to a particular attribute, but may be unstable with respect to another. A system, in this sense, can be thought of as an entity having infinite attributes.

For example, consider a chalkboard eraser. In order to describe whether it is stable, a particular attribute like its color, position, orientation etc. needs to be chosen. Say, one selects its orientation as the attribute. Consider a symmetrical duster that is standing on a flat surface. Let be the angle it makes with the vertical. At , it is in a meta-stable state (fig 1.4). If it is very slightly perturbed it returns back to this position. But if the perturbation is a bit larger it topples to the globally stable state (), because this state has lower energy.

Figure 1.4 Energy diagram for a chalkboard eraser