An industrial cooling line carries water through a horizontal steel pipe that contracts from an upstream diameter of 5.0cm to a downstream diameter of 3.0cm. A flow-meter installed in the smaller section registers a steady water speed of 5.0ms−1. The water is incompressible and the temperature is constant.
(a) Determine the average speed of the water in the wider upstream section.
(b) Calculate the percentage change in the water’s kinetic energy per unit mass as it moves from the upstream section to the downstream section. Express your answer to two significant figures.
(c) Briefly describe the physical reason the change computed in part (b) must be accompanied by a change in some other property of the water if the flow remains steady and horizontal.