9514 1404 393
Answer:
548 W
Step-by-step explanation:
The work done to raise 4 kg to a height of 12 m against gravity is ...
W = Fd = Mgd = (4 kg)(9.8 m/s²)(12 m) = 470.4 J
The power output of the pump doing this work each second is ...
P = (470.4 J)/s = 470.4 watts
Since the pump is only 86% efficient, the power input is ...
Pout = eff × Pin
Pin = Pout/eff
Pin = (470.4 W)/(0.86) ≈ 548 W
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<em>Additional comment</em>
The rating of a motor often has little to do with its actual input power or its ability to do work. The rating is used for purposes such as circuit-breaker and wire sizing, or other aspects of sizing the physical plant surrounding the motor (including piping, in the case of a pump). While we can calculate a value for input power, we cannot make any claim regarding the power rating of the pump.
