Use the microscopic equations of motion in Appendix $\mathrm{E}$ as a starting point to derive a relationship between the volumetric flow rate and the pressure gradient for a Newtonian fluid in a pipe that is valid for any orientation of the pipe axis. 

the critical starting point requires that you identify which velocity and velocity gradients are nonzero, and hence the corresponding nonzero stress components, for this problem. This allows you to tailor the differential