According to Bernoulli's principle, when the speed of a fluid increases, what happens to its pressure?

• A. Decreases
• B. Increases
• C. Remains the Same
• D. Fluctuates

Answer: (A)

Faster flow corresponds to more kinetic energy. Bernoulli's principle states that, along a streamline for an ideal, steady, incompressible flow, the sum of static pressure and dynamic pressure remains constant. Dynamic pressure is ½ρv², so when the velocity v increases, the static pressure p must decrease to keep the total pressure the same. This is why regions where fluid speeds up—such as through a constriction or over a wing—have lower pressure. In real fluids, viscosity and turbulence can cause deviations, but the basic relationship holds: higher speed means lower static pressure.