Question

One drop of soap bubble of diameter D breaks into 27 drops having surface tension σ. The change in surface energy is (a) 2πσD² (b) 4πσD² (c) πσD² (d) 8πσD²

Answer 1

Explanation:

Volume of bigger bubble = volume of 27 smaller bubbles

⇒

3

4

πD

3

=27×

3

4

πd

3

⇒d=

3

D

Initial surface energy S

i

=4πD

2

σ

Final surface energy S

f

=27×4πd

2

σ

ΔS=S

f

−S

i

and using d=

3

D

ΔS=σ×4π[27×

9

D

2

−D

2

]

=2D

2

×4π×σ=8πσD

2