The drag on a cruising airplane depends on its overall length b, flying speed V, air density rho, air viscosity μ, and speed of sound c. (a) Write this relationship in dimensionless form. The drag on the airplane cruising at 240 mph in standard air (14.7 psia) is to be determined from tests on a 1:10 scale model placed in a pressurized wind tunnel. To minimize compressibility effects, the air speed in the wind tunnel is also to be 240 mph. Determine (b) the required air pressure in the tunnel (assuming the same air temperature for model and prototype) and (c) the drag on the prototype corresponding to a measured force of 1 lb on the model.