Fluid Properties: Viscosity and Newton's Law of Viscosity

Viscosity is a measure of a fluid's resistance to flow. It is a property that describes how thick or thin a fluid is and is an important factor in determining a fluid's behavior in a particular system. The viscosity of a fluid is a measure of its internal resistance to flow and can be thought of as a fluid's "thickness" or "fluidity".

A fluid with a high viscosity, such as honey, is very thick and flows slowly, while a fluid with a low viscosity, such as water, flows more easily. The viscosity of a fluid can be affected by temperature, pressure, and the presence of other substances, and it can vary greatly between different fluids. For example, the viscosity of oil is much higher than that of water, which is why oil is said to be "thicker" than water.

The unit of viscosity is usually measured in Pascal seconds (Pa·s) or centipoise (cP). It's an intrinsic property of the fluid and is independent of the size or shape of the container or the amount of fluid present.

Viscosity is an important property in many fields including engineering, geophysics, and medicine, as it affects the flow of fluids in pipes, the deformation of objects in fluid, and blood flow in veins.