The forces F1 and F2 (see previous drawing) form a free couple, which is said to be the aerodynamic moment of the wind force or simply overturning moment Mw. This moment tries to rotate the bullet about an axis through the CG, perpendicular to the axis of symmetry of the bullet. The overturning moment tends to increase the angle of yaw.
The force FW, which applies at the CG can be split into a force, opposite to the direction of the movement of the CG (the direction of the velocity vector v), which is called the drag force FD or simply drag and a force, perpendicular to this direction, which is called the lift force FL or simply lift.
