Consider the steady laminar flow of a newtonian fluid with constant rho and µ in an annulus of length l formed between concentric cylinders of radius r and radius κr, where κ < 1. the pressure difference between the ends of the cavity is ∆p = pl − p0 < 0. the velocity field has the form: vr = vθ = 0, vz = vz(r, z). use differential balances for mass and z-direction momentum (neglecting gravity) to obtain an expression for the velocity profile vz(r). also, derive expressions for the average velocity hvzi and mass flow rate m