Crude oil (density p=847kg.m^-3, viscodity (mu)=0.002 Pa.s) flows in a circular pipe of radius R=30 cm. The maximum speed of the oil at the centre of the pipe is u(max)=0.5 m/s. the flow profile is such that u=u(max)*(1-(r/R)^2) where u is the flow speed and r is the distance from the centre of the pipe in the radial direction. What is the shear stress on the pipe wall? What is the shear force exerted by the oil on a 1m long section of the pipe?