Unit kPa s kilopascal second Dynamic Viscosity In the field of fluid mechanics, dynamic viscosity is a measure of a fluid's resistance to flow or deformation under an applied force or stress. It is defined as the ratio of the shear stress (force applied per unit area) to the shear rate (velocity gradient) within the fluid. The unit kPa s (kilopascal second) is a common unit for expressing dynamic viscosity. The kilopascal (kPa) is derived from the SI unit of pressure or stress, the Pascal (Pa), where 1 kPa = 1000 Pa. The "s" in "kPa s" stands for seconds, which is the unit of time. In this compound unit, the term kPa represents the stress, and second refers to the time. So, the unit kPa s represents the amount of stress (in kilopascals) applied to the fluid, over a specific time period (in seconds). To better understand this unit, consider a fluid whose dynamic viscosity is 1 kPa s. This means that if a constant shear stress of 1 kPa is applied to a given area of the fluid, it will result in a velocity gradient of 1 s-1. The higher the dynamic viscosity, the more resistant the fluid is to flow or deformation under the applied stress. Thus, kPa s is an essential unit in understanding and quantifying the behavior of fluids in various applications, such as lubrication, material processing, and fluid flow analysis.