Fluid Mechanics Viscosity Question 352
Question: 8000 identical water drops are combined to form a big drop. Then the ratio of the final surface energy to the initial surface energy of all the drops together is [EAMCET (Engg.) 2000]
Options:
A) 1 : 10
B)1 : 15
C) 1 : 20
D) 1 : 25
Show Answer
Answer:
Correct Answer: C
Solution:
As volume remains constant $ R^{3}=8000r^{3} $ $ \therefore R=20r $ $ \frac{\text{Surface energy of one big drop}}{\text{Surface energy of 8000 small drop}}=\frac{4\pi R^{2}T}{8000\ 4\pi r^{2}T} $ $ =\frac{R^{2}}{8000r^{2}}=\frac{{{\left( 20r \right)}^{2}}}{8000r^{2}}=\frac{1}{20} $
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