Aerodynamics is an advanced and complicated science. It is concerned with the study of the forces which operate on solid bodies passing through air. These forces are gravity, lift, drag and thrust. (a) gravity- the power which forces all solid bodies downwards to the surface of the earth: (b) list-the upward force which works in the opposite Direction of gravity pull: (c) drag- the force which pushes back objects which move forward, in other words, the resistance of the air against motion: and (d) thrust-the forward force Directed at overcoming the resistance of the air to motion.