According to Newton's second law of motion, if we have a rigid, unchanging mass and we observe it accelerating, what must be happening? Question 2 options: A force is being applied to the mass No force was or is being applied to the mass The mass MUST be changing A force was not applied.

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.