A windmill is used to raise water from a well. The depth of the well is 5.0 m. The windmill raises 204 kg of water every day. What is the average useful power extracted from the wind?
A. 12 mW
B. 120 mW
C. 690 mW
D. 1700 mW

Question

A windmill is used to raise water from a well. The depth of the well is 5.0 m. The windmill raises 204 kg of water every day. What is the average useful power extracted from the wind? 
A. 12 mW
B. 120 mW
C. 690 mW
D. 1700 mW

michele_laino · Answer

The requested average power P, is given by the subsequent formula:
$$\Large  P = \frac{{mgh}}{{\Delta t}}$$
where m is the mass of water, h is the depth of the well, g is gravity, and \Delta t are the seconds contained in 1 day
In that way the power will be measured in watt

pythagoras123 · Answer

I got 204 x 9.81 x 5 = 10006.2 kJ
Power = 10006.2 kJ / 1 = 10006.2 kW = 10.0062 mW which doesn't fall under any of the options. Did I misinterpret something here

anonymous · Answer

First of all it will be joules not kilo joules
secondly you are given the time as 1 day not 1 second
$$\Delta t=1day=24\times60\times60 seconds$$

anonymous · Answer

$$P=\frac{10006.2}{24\times60\times60} Watt$$