If the resistance to motion, R, of a sphere through a fluid is a function of density, and viscosity, of the fluid, and the radius, r and velocity, u of the sphere, show that R is given by: R=2f(ur) (b) Hence at very low velocities, the resistance, R is proportional to the velocity, u then, show that, R=kru, where k is a dimensionless constant. A fine granular material of specific gravity, 2.5 is in uniform suspension in still water of depth 3.3m. Regarding the particles as spheres of diameter 0.002cm, find how long it will take for the water to clear. Take k=6 and =0.0013kg/ms. (Use Buckinghams Pi Theorem with three repeating variables)