$11-85.$ A $3-$Mg airplane is flying at a speed of $70\frac{m}{s}.$ If each wing can be assumed rectangular of length $5$ m and width $1\mathrm{.}75$ m $,$ determine the smallest angle of attack $$ to provide lift assuming the wing is a NACA $2409$ section. The density of air is $=1\mathrm{.}225k\frac{g}{m^3}\mathrm{.}11-85.$ A $3-$Mg airplane is flying at a speed of $70\frac{m}{s}.$ If each wing can be assumed rectangular of length $5$ m and width $1\mathrm{.}75$ m $,$ determine the smallest angle of attack $$ to provide lift assuming the wing is a NACA $2409$ section. The density of air is $=1\mathrm{.}225k\frac{g}{m^3}.$