1. The problem statement, all variables and given/known data 2. Relevant equations Power = Work Done / Time Work Done = Force * Displacement PE = mass * gravity * height 3. The attempt at a solution I got the first part (i) right, so the mass of the sea water is 1.32 x 10^12 kg. Part (ii) is the bit I am stuck on. My thoughts were that it must fall 10m, so the max loss in PE is (1.32 x 10^12)(9.81)(10), but the mark scheme says the height is 5m, so that it is (1.32 x 10^12)(9.81)(5). Why do we take the height to be 5m here when it falls through 10m?