Which statement reflects Bernoulli's principle?

• A. When fluid velocity increases, pressure at that point decreases
• B. When velocity increases, temperature increases
• C. Pressure is independent of velocity
• D. Velocity and pressure both increase when velocity rises

Answer: (A)

Bernoulli's principle describes how energy is shared between pressure and motion in a moving fluid. Along a streamline, if the flow is steady and the fluid is incompressible and has negligible friction, the sum of static pressure and kinetic energy per unit volume remains constant (and height if relevant adds potential energy). So when the fluid speeds up, its static pressure must fall to keep the total energy the same. That makes the statement that velocity increases while pressure decreases the best reflection of Bernoulli’s principle. The other ideas aren’t part of this direct relationship: temperature isn’t determined solely by velocity in Bernoulli’s equation, pressure isn’t independent of velocity along a streamline, and increasing velocity doesn’t inherently raise pressure. In aviation terms, this explains why faster air over a wing has lower pressure, contributing to lift.