Newton's Law of Viscosity

Newton's law of viscosity states that shear stress between adjacent fluid layers is porportional to the velocity gradients between the two layers.  The ratio of shear stress to shear rate is a constant for a given temperature and pressure.

 

Newton's Law of Viscosity formula
\(\large{ \tau = \mu\; \frac {d \nu}{dy}  }\)
Symbol	English	Metric
\(\large{ \tau }\)  (Greek symbol tau) = shear stress	\(\large{ \frac{lbf}{in^2} }\)	\(\large{ Pa }\)
\(\large{ \mu }\)  (Greek symbol mu) = dynamic viscosity	\(\large{\frac{lbf-sec}{ft^2}}\)	\(\large{ Pa-s }\)
\(\large{ \frac {d \nu}{dy} }\) = rate of shear deformation	\(\large{\frac{ft}{sec}}\)	\(\large{\frac{m}{s}}\)