To measure viscosity of newtonian fluids, one standard approach is to use a couette viscometer. in this device, a stationary cylinder (radius, ar) is inside a larger cylinder (radius, r). fluid is placed between the two cylinders and the outer cylinder rotates at an angular velocity ws-1. the gap between the cylinders is much smaller than the overall height and gravity acts only in the z-direction. at steady state, what is the velocity expression of the fluid?