Q.

If 1000 droplets of water of surface tension 0.07 N/m, having same radius 1 mm each, combine to form a single drop, In the process the released surface energy is (Take π=227)                        [2023]

1 7.92×10-6 J  
2 7.92×10-4 J  
3 9.68×10-4 J  
4 8.8×10-5 J  

Ans.

(2)

1000×4π3(1)3=4π3R3

R=10 mm

T×1000×4π(10-3)2-T×4π(10×10-3)2=ΔE

ΔE=4×π×7×10-2[1000-100]×10-6

ΔE=7.92×10-4 J