# Relationship between static pressure and dynamic pressure in a fluid

Curiosity Science Physics Relationship between static pressure and dynamic pressure in a fluid

• Is the pressure at the surface of a flowing water open to the atmosphere less than that of a stationary (not flowing) water?

The question is about the relationship between static and dynamic pressure. I want to know if the pressure at the surface of say a lake (stationary) is greater than that of a flowing lake? Does the flow velocity also have an effect?

– Bryan, via the Ask a science question page.

• The distinction can be better understood if you look at the energy of the fluid with respect to its motion. When the fluid is stationary, i.e when there is no motion, the fluid has no kinetic energy. Which means, the pressure in the fluid is solely due to the potential energy. This is the static pressure of that fluid. But when the fluid is in motion, the potential energy would decrease, while the kinetic energy would increase. Now there is a pressure acting along the stream. This is the dynamic pressure.