How would I find an expression for average velocity in a smooth pipe, which is dependant on the viscosity, diameter, and pressure gradient (dp/dx) ?

liquid (density 800kg/m3, viscosity 10−3 kg/ms) has to be supplied at a mean speed of 2m/s through a pipe of diameter 12.5mm with a surface roughness equivalent to that for structural steel. What is the magnitude of the pressure gradient necessary to achieve this flow? Your answer should have a positive sign and be to the nearest 10 Pa/m. You may wish to use the Moody diagram.

Liquid flows at a rate of 1.5 L/min in a circular tube with a diameter of 5 mm. inside a circular tubeThe vascular endothelial cells are attached. One cell has a surface area of 500 μm2. To be attached to the inner wall of the tube. What force does one cell have to withstand? The viscosity of the liquid is 1.2 cP = 0.0012 Pass.