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Rural hygiene

The sealed septic tank of a country cottage has accumulated toxic gases under an absolute pressure of 125 kPa. The cottage owner wants to release these gases from a safe distance by opening the hinged, square, trapdoor of the tank by pushing it with a high speed water jet provided by a nozzle, as shown in the figure. The nozzle exit diameter is 55 mm, while the smooth hose connecting the nozzle to a pump has an inner diameter of 100 mm. The pump is drawing water from a well through the same type of smooth hose. The total length of the hose, including the suction length, is 35 m. Additional information is provided in the figure.
a) Determine the speed of the water jet that will open the trapdoor.
b) Determine the power consumed by the pump when the door opens, if its efficiency is 78%.

Contributed by Stavros Tavoularis, Department of Mechanical Engineering, University of Ottawa, Ottawa, Canada.

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