ABSTRACT
In principle, determining friction coef cients seems straightforward: one simply measures the normal force or weight of an object and the force resisting relative tangential motion between it and a counterface. Investigators have measured frictional quantities for centuries by using ramps, pulleys, spring scales, and similar devices. Yet, basic researchers who envision friction as the net result of nanoscale interaction, and engineers who attempt to simulate the frictional environment within speci c device employ more sophisticated and elaborate techniques. Some employ strain gauges, de ecting beams, and piezoelectric force sensors, and others have devised ways to infer the magnitude of friction indirectly.
