An incompressible Newtonian fluid flows steadily between two infinitely long, concentric cylinders of radius ri and ro, for the inner and outer cylinders, respectively. Outer cylinder is fixed and the inner cylinder moves horizontally with a uniform velocity Vi. Assuming laminar, axisymmetric and fully-developed flow, determine the velocity distribution in the gap. Find expression for Vi (in terms of other relevant variables) that the drag on the inner cylinder becomes zero.