What does the equation A1V1 = A2V2 express in terms of airflow?

The equation ( A_1V_1 = A_2V_2 ) is derived from the principle of conservation of mass, specifically applied to a fluid (in this case, air) moving through a varying cross-sectional area. This equation states that the mass flow rate (the product of the cross-sectional area ( A ) and the airflow velocity ( V )) remains constant along a streamline in an incompressible flow.

In practical terms, when the cross-sectional area of a duct or passage decreases, the velocity of the airflow must increase to maintain constant mass flow. Conversely, if the area increases, the airflow velocity decreases. This relationship is critical in aerodynamics and fluid dynamics, as it helps predict how changes in area affect the velocity of airflow.

Thus, the correct understanding of this equation is that mass airflow remains constant with changes in the area through which the fluid is flowing, supporting the choice regarding mass airflow being constant with area. The other options misconstrue the implications of changes in area, such as suggesting independence of velocity from area, or suggesting that pressure and aerodynamic forces behave uniformly throughout varying areas, which are not direct implications of the equation given.