ABSTRACT
When a bow is gently pulled across a violin string to produce a rich C note, it sounds very elegant and simple. In analyzing the source of the sound — the sliding of a bow with resin over a tuned string — the physics seems simple. At first glance is would appear that the “lubricating” resin would be undergoing Couette flow between the bow and the string, but such dynamics would not produce the resonance in the string. Instead, it is the far more complex stick-slip type of frictional sliding between the moving parts that excites the resonance and creates the sound. Other similar examples such as door hinges or wheel bearings are ideally described by engineering hydrodynamics. However, when the door creaks or the wheel squeaks, there is a transition from a system described by bulk lubrication to a system controlled by microtribology (or what is now referred to as nanotribology).
