1. The problem statement, all variables and given/known data Some electric-power companies use water to store energy. Water is pumped by reversible turbine pumps from a low to high reservoir. To store the energy produced in 1.0 hour by a 120*106 electric-power plant, how many cubic meters of water will have to be pumped from the lower to the upper reservoir? Assume the upper reservoir is 520 m above the lower and we can neglect the small change in depths within each. Water has a mass of 1000 kg for every 1 m3 2. Relevant equations P=W/t W=Fd F=ma 3. The attempt at a solution I multiplied power by the total number of seconds in an hour to get work. I then divided the work by the distance of 520 m and I get force. This is where I'm stuck at. I have that force is equal to (120000000 kg*m2/s3)*(3600s)/(520m). I don't know how to solve for mass because it seems that the flow has a constant velocity and there is no acceleration. Can someone please point me in the right direction?