In the summer of 2002, a group of miners in Quecreek, Pennsylvania, became trapped 240 ft underground when a section of the coal seam they were working collapsed into an adjacent, but abandoned, mine that was not shown on their map. The area became flooded with water, and the miners huddled in an air pocket at the end of a passageway until they were safely rescued. As the first step in the rescue operation, holes were drilled into the mine to provide the miners with warm fresh air and to pump out the underground water. Neglecting friction in the pipes and the inefficiency of the pumps themselves, what average power would be required to remove 20,000 gal of water from the mine each minute? Express your answer in the units of horsepower. The density of water is listed in Table 6.1.

Table 6.1

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Density, p Viscosity, u Fluid kg/m? slug/ft kg/(m - s) slug/(ft s) Air 1.20 2.33 x 10-3 1.8 x 10-5 3.8 x 10-7 Helium 0.182 3.53 x 10-4 1.9 x 10-5 4.1 x 10-7 Freshwater 1000 1.94 1.0 x 10-3 2.1 x 10-5 Seawater 1026 1.99 1.2 x 10-3 2.5 x 10-5 Gasoline 680 1.32 2.9 x 10-4 6.1 x 10-6 SAE 30 oil 917 1.78 0.26 5.4 x 10-3