Newton proposed that stress shear between layers of flow variation corresponds to the changes between the speed (velocity gradient), which is equal to the derivative of the velocity in comparison with the vertical distance of the scene is.
Newton proposed that the shear stress is proportional to the fluid between the layers. The change between the top speed (velocity gradient), which is equal to the derivative of speed versus distance that is perpendicular.
Newton suggest that shear stresses between layers fluid variation match. Changes in speed between the layers (velocity gradient), which equals the derivative of velocity versus distance in the vertical, that is