# The New Student's Reference Work/Viscosity of Liquids

**Viscos′ity of Liquids,** a term employed in physics to describe a kind of friction between the particles of a liquid when the various parts of the liquid are moving with different velocities. If a surface of area, *A*, in the liquid be chosen in a plane parallel to one of the fixed walls of the vessel, then the viscosity of the liquid is expressed as follows: Let *V* denote the velocity with which the liquid is moving at the surface *A*; and let *D* be the distance from the surface *A* to the fixed parallel wall.

Then if *R* is the tangential resistance experienced by the plane *A*,

where *n* is a constant for any one liquid and is called the *coefficient of viscosity* for that liquid. This coefficient is the measure of the viscosity of any liquid. It is the viscosity of water that causes waves to die down after a storm.