Municipal engineers must ensure that water delivered to homes on the top floor of a 40-story apartment building emerges from the tap at essentially the same rate as water delivered to houses at ground level. Water is often treated as an "ideal" fluid when performing preliminary calculations for such systems.
Consider the following real-world context:
• The city main at street level supplies water at a pressure of 410 kPa.
• Vertical supply pipes inside the building rise 120 m from the main to the highest apartment.
• Under ordinary operating conditions the volumetric flow rate through each apartment’s branch pipe is only a few liters per minute.
Answer the questions below in the order asked. Respond with clear, well-organized reasoning and use precise physics terminology.
(a) Describe two defining characteristics of an ideal fluid and explain, in words only, how each characteristic simplifies the analysis of fluid motion in pipes.
(b) For the apartment building described, justify whether the assumption of incompressibility is reasonable for the water supply. Your justification should reference relevant physical quantities and typical magnitudes.
(c) Identify one situation that could arise in this building in which water viscosity can no longer be neglected. Explain qualitatively how ignoring viscosity in that situation would lead to an incorrect prediction about either flow rate or pressure.
(d) Suppose emergency pumps are activated, doubling the volumetric flow rate through the vertical supply pipe for several minutes. Explain why the choice of treating water as an ideal or real fluid becomes more significant under these conditions, and state which of the two ideal-fluid assumptions is most likely to break down first.