Water at a density of 998 kg m and kinematic viscosity of 1 x 10-6 m s flows through smooth tubing at a mean velocity of 2 m s. If the tube diameter is 30 mm, calculate the pressure gradient per unit length necessary. Assume that the friction factor for a smooth pipe is given by 16/Re for laminar flow and 0.079/Re1/4 for turbulent flow.