physics !!!!1?

Question

the pipes leading to the showers in your locker room are old and inadequate. while the city water pressure is 700,000 Pa, the pressure in the locker room when one shower is on is 600,000 Pa. Use poiseuille's equation to calculate the approximate pressure if three shower are on.

P.S. is it trick question. the anser is 400,000 Pa . Please help me out

Answer 1

Poiseuille's law says that the volume of fluid flowing through a pipe is proportional to the difference in pressure.

http://en.wikipedia.org/wiki/Poiseuille's_law

If one shower's worth of water requires a pressure difference of 100,000 Pa between the city main and locker room, then three showers' worth of water, being three times as much water, would require three times the pressure drop or 300,00 Pa between the city main and the locker room. 700,000 - 300,000 = 400,000

The only trick is the assumption that with the somewhat lower water pressure all three showers get the same amount of water as the one shower did. But this simplification is normal for school problems.