ABSTRACT
Friction is the resistance to the sliding of one solid body over or along another, as solid bodies are ordinarily understood in the macroscopic world. High friction is desirable between tires and roads (coefficients of which range from about 0.5 to 1.2), between mechanical parts that are bolted together and in countless other examples. Low friction is desirable between sliding parts in computer hard disk systems, in engines, in door latches and in many other mechanical devices. Whether friction is low or high is of little consequence in many applications, provided it is predictable (i.e., reasonably constant) and does not cause noise or vibrations. The most notable exception to the latter is the stringed instrument that uses a bow to create music.
