A pyramid has a square base and four faces, which are equilateral triangles. A charge Q is placed on the center of the base of the pyramid. What is the net flux of electric field ΦE,1ΦE,1 emerging from one of the triangular faces of the pyramid? Express your answer in terms of Q and the permittivity of free space, 0.

The ratio of lift to drag l/d for a wing or airfoil is an important aerodynamic parameter, indeed, it is a direct measure of the aerodynamic efficiency of the wing. if a wing is pitched through a range of angle of attack, l/d first increases, then goes through a maximum, and then decreases. consider an infinite wing with an naca 2412 airfoil. estimate the maximum value of l/d. assume that the reynolds number is 9x10^6.