A cubical vessel of height 1m is full of water.The minimum work done in taking water out from the vessel will be???

let us take an elemental lenght along the height of the vessel dx at a height x

let the area of the basse of  the cube be A

thus the volume of that elemental strip will be: A dx

and potential energy will be : xg(A dx)p

where p is the density of water

 

thus total potential energy can be found out by integrating this along the whole height of the cube: gAp(1/2)

this will be the work dont to take the whole water out.