Bernoulli's principle states that as the velocity of a fluid increases:

Bernoulli's principle (Daniel Bernoulli, 1738): for a flowing fluid, faster flow = lower pressure. Conversely, slower flow = higher pressure. This is a consequence of conservation of energy in flowing fluids: kinetic energy (motion) + pressure energy + gravitational potential energy = constant. Faster motion → more kinetic energy → less pressure energy. Real-world examples: (1) AIRPLANE LIFT — wings shaped so air moves faster over the top (curved upper surface) than the bottom (flat or less curved); faster top = lower pressure above; slower bottom = higher pressure below; net upward force = lift; (2) CARBURETORS / SPRAY BOTTLES — fast air stream through a venturi (narrowed section) creates low pressure that draws up fuel/liquid; (3) BASEBALL CURVES — spinning ball drags air faster on one side, creating pressure difference and curving the trajectory; (4) ROOFS LIFTED OFF IN STORMS — high winds over roof create low pressure above; interior pressure stays normal; pressure difference can push roof off; (5) SHOWER CURTAIN PULLED INWARD — running water creates low pressure inside the shower; (6) CHIMNEYS — fast wind across the top pulls smoke up. Venturi effect: narrow section in a pipe causes fluid to speed up (continuity equation: A₁v₁ = A₂v₂); speeding up causes pressure to drop (Bernoulli). Pitot tubes measure airspeed by measuring this pressure difference. Despite being central to aerodynamics, Bernoulli's principle is often misunderstood — it applies to ideal flow along streamlines without friction, viscosity, or compressibility effects; real aerodynamics combines Bernoulli with other effects. ASVAB MC tests the basic concept.