What is a common source of parasite drag?

Parasite drag primarily arises from the interaction between the aircraft's surface and the surrounding air. As an aircraft moves through the atmosphere, air friction occurs along its surfaces, which creates resistance to the aircraft's forward motion. This is known as form drag, one component of parasite drag, while skin friction drag contributes to it as well, derived from the smoothness or roughness of the aircraft's surface.

In this context, airflow friction over the aircraft is the most relevant reason for parasite drag. The amount of parasite drag increases with the square of the velocity, meaning that at higher speeds, the impact of this friction is more significant, resulting in greater resistance.

The other factors mentioned do not directly contribute to parasite drag. While lift creation relates to induced drag and is crucial for overall aerodynamic performance, it does not pertain to the definition of parasite drag. Wind shear effects can influence the stability and control of the aircraft but are not a primary cause of parasite drag. Finally, changes in weight distribution primarily impact the aircraft's center of gravity and performance but do not generate parasitic drag directly.