quoted by Pappus; he considers the mechanics of a bent lever. Pappus uses this principle of Heron to discuss the problems of the power (force) required to move a weight up an inclined plane. He imagines the weight as located at the center of a sphere being rolled up the inclined plane and balanced by a fictitious weight B on the surface of the sphere at the same elevation as the center and as close as possible to the plane (see Fig. 1). He takes the power required as the sum of the power required to move the two weights along a horizontal surface. (This reasoning uses Aristotelian principles of physics that we no longer accept. On the modern view, except to overcome rolling friction, no force at all is required to roll a ball along a horizontal surface once it has started to roll.) Thus, although the principle of the lever was well understood in Hellenistic times, that of the inclined plane was not. Since the modern laws involves only the proportions in a triangle, it seems strange that this simple principle was not discovered. (Cooke, 146,147.)
             Figure 1: The law of the inclined plane according to Heron and Pappus.
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