An airplane flies on a level path. There is a pressure difference of 540 Pa between the lower and upper surfaces of the wings. The area of each wing surface is about 150 m^2. The air moves below the wings at a speed of 81.0 m/s. (a) Estimate the weight of the plane. (b) Estimate the air speed above the wings. I figured out (a) weight of plane. (150 m^2)(540 Pa) = 81,000 N I am having trouble figuring out the air speed. I am guessing that I have to use Bernouli's equation b/c there are two different points (upper and lower surfaces). When using Bernouli's equation, don't I need density ? How can I find density if no mass is given?