A circular swimming pool has a diameter of 12 m, the sides are 4 m high, and the depth of the water is 3.5 m. How much work (in Joules) is required to pump all of the water over the side? (The acceleration due to gravity is 9.8 m/s^2 and the density of water is 1000 kg/m^3.)

Question

anonymous · Answer

I just wanna know where 2.25 from this came from

Volume of the water is π (6 m)² (3.5 m) = 395.841 m³.
The mass of the water is 395841 kg.
Center of mass of the water is 2.25 m below the side.
The work required is

anonymous · Answer

The water is between -4m and -0.5m from the top of the swimming pool. So the centre of mass of the water is in the middle of those two points, at (0.5 + 4)/2 = 2.25m from the top of the swimming pool.