Using the general linear momentum balance equations and the Newtonian constitutive equations relating the viscous stresses to the fluid velocity gradients reported at the end of the question, obtain the following simplified equations of motion: 8,p = pg, ; Op = pggr ; 0;p = (1/r)D,rD,v,(r)] in which g, and g, are the radial and angular components of the gravitational field g. State clearly the reason for each simplification that you make. [2/25]