The forward pressure of a stream of water as it leaves an orifice (nozzle) is called ______.

• A. Flow pressure
• B. Velocity pressure
• C. Static pressure
• D. Residual pressure

Answer: (A)

The main idea here is that the forward push of a jet comes from the energy of the moving water itself. When water flows through a nozzle and exits, part of its energy appears as a pressure term tied to the motion, not just the static pressure in the fluid. This dynamic pressure is proportional to the velocity squared (p_dynamic = ½ ρ v^2). Some hydraulics texts call that the flow pressure, since it represents the pressure generated by the flow itself.

So, the forward thrust of the jet is described by this flow (dynamic) pressure, distinguishing it from static pressure (the pressure regardless of motion) and from residual pressure (leftover pressure elsewhere in the system). At the nozzle exit, the static pressure is often near atmospheric, while the forward effect of the jet is governed by the flow/velocity pressure.