Equation 11-28 says that the greater the viscosity \(\eta\), the greater the force that must be applied to move one plate relative to the other. The units of viscosity are pascals times seconds, or Pa \(\cdot\) s for short. Viscosities are also sometimes given in poise, named for the nineteenth-century French scientist Jean Poiseuille; 1 poise equals 0.1 Pa \(\cdot\) s.