NACA (“NACK-uh”) developed a standard set (10[1])of these devices (10[2])with four (10[1])or five digit (10[1])identifiers. (10[3])Effects like downwash (10[2]-5[1])for finite (10[1])versions of these objects are simulated (10[1])by modelling (10[2])these objects as an infinite set of filaments in a theory named for Prandtl (“PRAWN-tull”). The force per unit length (10[1])on these devices is proportional (-5[1])to the line integral of the tangential velocity (10[1]-5[1])around them, (10[1])according to the Kutta–Joukowski (10[5])(“KOO-tuh zhoo-KOFF-skee”) theorem. (10[8]-5[1])The chord (10[1])line (10[3])connects these (10[1]-5[1])devices’ (10[1])leading (10[1])and trailing edges, (10[1]-5[1])while the difference (10[1])in convexity (10[3])of their upper (10[1]-5[1])and lower surfaces (10[4])is called their camber. (10[8]-5[1])These (-5[1])objects (10[1]-5[1])enter (10[1]-5[1])a stall (10[1]-5[1])when (-5[1])they exceed (10[3])the critical (10[1])angle (10[2]-5[2])of attack. (10[9]-5[2])For 10 (10[1]-5[1])points, (10[3])name these devices (10[2])that generate lift (10[2])while (10[2])moving (10[4])through (10[1])air. (10[3])■END■ (10[19]0[3])