The velocity distribution for flow over a flat plate is given by u = y - y, where u is the point velocity in meter per second at a distance y meter above the plate. Determine the shear stress at y = 9 cm. Assume dynamic viscosity as 8 poise. Determine the minimum size of glass tubing that can be used to measure water level, if the capillary rise in the tube is not to exceed 0.25mm. Take surface tension of water in contact with air as 0.0735 N/m.