The radius of a well is 7m. Water in it is at a depth of 20m and depth of water column is 10m. Work done in pumping out water completely from the well is, (g=10ms−2).
Total mass of water =m
m= density ×volume
By using center of mass concept ,center of mass of water is at depth of (20+5)h from the top.
Hence work done =mg(20+5)