Which principle explains that as the velocity of a fluid increases, its internal pressure decreases?

• A. Bernoulli's Principle
• B. Newton's Second Law
• C. Pascal's Law
• D. Charles' Law

Answer: (A)

Bernoulli's principle says that in steady, incompressible, frictionless flow along a streamline, the sum of static pressure and dynamic pressure remains constant. As the fluid speeds up, its static pressure decreases because more of the energy is carried as kinetic energy. This inverse relationship between speed and pressure explains why air travels faster over the wing surface and presses less against it, producing lift.

The other options don’t describe this specific velocity–pressure relationship in flowing fluids. Newton's Second Law governs forces and acceleration but not the particular tradeoff between speed and pressure in a streamline flow. Pascal's Law deals with pressure transmitted uniformly in a contained fluid, not how velocity changes pressure. Charles' Law connects volume and temperature for gases at constant pressure, not fluid flow pressure effects.