Water flows over a section of Niagara Falls...?

Question

Water flows over a section of Niagara Falls at the rate of 1.0 x 10^6 kg/s and falls 48.0 m. How much power is generated by the falling water?
_W

Answer 1

P = W / t

In one second, 1*10^6 kg of water goes over the falls. The water's potential energy is converted to kinetic energy when landing at the bottom of the falls. That kinetic energy is the ability to do work. So we can say that

W at the bottom = potential energy when at the top = m*g*h
W = 1*10^6 kg * 9.8 m/s^2 * 48 m
W = 1*10^6 * 9.8 * 48 Joules

Power = 1*10^6 * 9.8 * 48 Joules / 1 s
And 1 Joule/s is 1 Watt