The core idea: As the speed of a fluid (liquid or gas) increases, the pressure within the fluid decreases. Conversely, when the speed of a fluid slows down, the pressure increases.

Imagine a fluid flowing through a pipe with a narrow section in the middle. As the fluid reaches the narrower part, it has to squeeze through, causing its speed to increase. According to Bernoulli's principle, this increase in speed is accompanied by a decrease in pressure in the constricted area. Once the fluid passes the narrow section and enters a wider area again, its speed slows down, and the pressure rises back up.

Why is this important?

Bernoulli's principle has numerous applications in various fields:

Flight: It explains how airplane wings generate lift. The curved shape of the wing forces air to travel faster over the top compared to the bottom, creating a pressure difference that lifts the aircraft.
Carburetors: In car engines, Bernoulli's principle helps draw fuel into the engine by creating a low-pressure zone near the intake valve.
Anemometers: These instruments use Bernoulli's principle to measure wind speed. The faster the wind blows, the lower the pressure it exerts on a small object, which can be measured to determine wind speed.

Remember: Bernoulli's principle applies to ideal fluids in steady, or streamlined, flow. Real-world fluids have viscosity, which can cause energy losses and affect pressure changes.