What is the definition of air density?

The definition of air density is the mass of air particles per unit of volume. This means that air density quantifies how much mass of air is contained in a specific volume, which is usually measured in kilograms per cubic meter (kg/m³). Understanding air density is essential in aerodynamics because it affects various factors such as lift, drag, and overall aircraft performance. When the density of air changes, such as due to altitude or temperature variations, it directly impacts these aerodynamic characteristics.

For example, at higher altitudes where the air density is lower, aircraft may produce less lift and require longer takeoff distances. Similarly, air density plays a crucial role in the calculations of engine performance and fuel efficiency. Therefore, recognizing that air density is fundamentally about the mass of air within a certain volume is key in the study of aerodynamics.