Man's Role in Changing the Face of the Earth

The two types of force that are met most frequently in mechanics are gravity and friction. The former has been studied by great men of science in every age. The latter has been largely neglected, it being assumed that the sliding process holds little intrinsic in­ terest and that three simple laws, all dis­ covered before 1800, adequately de­ scribe the force of friction. However, the advent of modern machinery, working with very close tolerances under new and widely varying conditions, has shown up the inadequacy of our knowl­ edge of the sliding process. To give but two examples, jet engines and heat-ex­ changer pumps in nuclear power plants present lubrication problems never be­ fore encountered. Consequently the laws of friction have recently been restudied, and new facts discovered. This article will deal with the stick-slip phenom­ enon, an important by-product of sliding which produces most of the creaking, squealing, chattering and squeaking we hear in our everyday lives. by Ernest Habinowicz