What happens to the speed of a fluid as it passes through a narrow section of a pipe?

When a fluid flows through a pipe and encounters a narrower section, the speed of the fluid increases. This phenomenon can be explained by the principle of conservation of mass, which states that for an incompressible fluid (such as most liquids), the mass flow rate must remain constant throughout the pipe.

As the cross-sectional area of the pipe decreases, the same volume of fluid must pass through that smaller area in a given amount of time. To maintain the flow and comply with this principle, the fluid must move faster as it enters the narrower section. This is also in line with Bernoulli's principle, which indicates that as the velocity of a fluid increases, its pressure decreases. Therefore, the correct response is that the speed of the fluid increases as it passes through the narrow section of the pipe.

In contrast, the other options would not align with these fundamental principles of fluid dynamics. A decrease in speed or constant speed would imply an inconsistency in flow continuity or incorrect assumptions about pressure and area relationships. Fluctuation would imply instability which is not typical in the steady flow of incompressible fluids in a uniform system.