Q.

A big drop is formed by coalescing 1000 small droplets of water. The surface energy will become                              [2024]

1 100 times  
2 10 times  
3 1100th  
4 110th  

Ans.

(4)   

         Lets say radius of small droplets is r and that of big drop is R,

         By conservation of volume:

         43πR3=100043πr3R=10r

           Surface energy of 1000 droplets

         Ui=1000(4πr2S)

         Uf=4πR2=100(4πr2S)

         Uf=110Ui