Q.

Two cylindrical vessels of equal cross-sectional area of 2 m2 contain water upto height 10 m and 6 m, respectively. If the vessels are connected at their bottom, then the work done by the force of gravity is: (Density of water is 103 kg/m3 and g=10 m/s2)          [2025]

1 1×105 J  
2 4×104 J  
3 6×104 J  
4 8×104 J  

Ans.

(4)

Uinitial=(ρA×10)g×5+(ρA6)g×3

Uinitial=ρAg(50+18)=68ρAg

Ufinal=(ρA×16)g×4=(ρAg)×64

W=U=68ρAg64ρAg=4ρAg

W=4×1000×2×10=8×104 J