Consider an airfoil in a wind tunnel (i. e., a wing that spans the entire test section). Prove that the lift per unit span can be obtained from the pressure distributions on the top and bottom walls of the wind tunnel (i. e., from the pressure distributions on the walls above and below the airfoil). Hint: Something similar was done for the drag force in section 2.6. You can follow that process, but this is a good bit less complicated.