# Consider an NACA \(2412\) airfoil with a \(2\;m\) chord in an airstream with a velocity of \(50\; m/s\) at standard sea level conditions. If the lift per unit span is \(1353\; N\), what is the angle of attack?

We need to find here the angle of attack.Lift per unit span is \[{L}’=\frac{1}{2}\rho _{\infty}V_{\infty}^{2}sc_{l}\]

\[q_{\infty}=\frac{1}{2}\rho _{\infty}V_{\infty}^{2}=\frac{1}{2}\times1.23\times50^{2}=1538\;N/m^{2}\]

\[c_{l}=\frac{{L}’}{q_{\infty}s}=\frac{1353}{1538\times2}=0.44\]

For NACA \(2412\) airfoil coefficient of lift of \(0.44\) is at \(2\) degrees angle of attack.