What does Bernoulli's principle state?

Bernoulli's principle is fundamental in understanding how lift is created in aviation. It states that in a flowing fluid, an increase in velocity occurs simultaneously with a decrease in pressure. This principle is crucial in explaining how airfoil shapes generate lift.

When air flows over the curved upper surface of an airfoil, it must travel faster than the air moving beneath the wing, leading to a reduction in pressure on the top surface. This difference in pressure between the top and bottom surfaces of the wing creates an upward lift force, allowing the aircraft to fly. The relationship described by Bernoulli's principle is central to aerodynamics, as it outlines how variations in airspeed relate to changes in pressure, thus driving the basic mechanics of how wings function.

Other options touch upon related concepts but do not encapsulate the essence of Bernoulli's principle: the influence of air density on lift is a factor, but not a direct statement of Bernoulli's principle itself; all parts of an airfoil do not have equal velocity; and while high-speed airflow is associated with low pressure, it does not specifically define the relationship dictated by Bernoulli's principle.