Chapters 7 , 8 and 9 focus on the formulation and solution of governing differential equations (one for mass balance and three for linear momentum balance) to determine pressure and velocity fields in fluids under various conditions of interest. Solutions of these differential equations allow us to compute values of many important quantities of interest at each point in the flow field at each time. Such detail is often necessary, as, for example, to compute wall shear stress from velocity gradients, which, in turn, can be correlated with mechanosensitive responses of various cells.