Alternative methods of solving the Couette vis-cometer problem by use of angular momentum concepts  (Fig. 3.6-1). 

(a) By making a shell angular-momentum balance on a thin shell of thickness ∆r, show that d/dr(r2τ_rθ) = 0 Next insert the appropriate expression for τ_rθ in the gradient of the tangential component of the Then solve the resulting differential equation boundary conditions to get Eq. 3.6-29. 

(b) Show how to obtain Eq. 3C.4-1 from the equation of change for angular momentum given in Eq. 3.4-1.