JEE Mains · Physics · STD 11 - 9.2 surface tension
A big drop is formed by coalescing \(1000\) small droplets of water. The surface energy will become _______.
- A \(100\) times
- B \(10\) times
- C \(\frac{1}{100}\) th
- D \(\frac{1}{10}\) th
Answer & Solution
Correct Answer
(D) \(\frac{1}{10}\) th
Step-by-step Solution
Detailed explanation
Lets say radius of small droplets is \(r\) and that of big drop is \(R\) \(\frac{4}{3} \pi R^3=1000 \frac{4}{3} \pi r^3\) \(R=10 r\) \(U_i=1000\left(4 \pi r^2 S\right)\) \(U_f=4 \pi R^2 S\) \(=100\left(4 \pi r^2 S\right)\) \(U_f=\frac{1}{10} U_i\)
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