Final answer:
Water velocity is converted to a pressure higher than suction pressure but lower than inlet pressure in a narrowing hose or nozzle due to the Bernoulli effect, which allows increased speed and thus, decreased pressure in the nozzle.
Step-by-step explanation:
The velocity of water is converted to a pressure higher than the suction pressure but lower than the inlet pressure within a narrowing hose or nozzle, a phenomenon that occurs due to the law of conservation of energy as expressed in the Bernoulli equation which balances the kinetic and potential energy in a moving fluid. This effect is clearly illustrated in situations involving a fire hose or a sump pump. As per the continuity equation and Bernoulli's principle, when water flows through a narrowing tube, such as a fire hose nozzle, its velocity increases, leading to a decrease in pressure within the narrowed section compared to the larger hose diameter behind it. The reduced pressure in the nozzle is still sufficient to expel the water due to the kinetic energy it gains with increased speed.