JEE Mains · Physics · STD 11 - 9.1 fluid mechanics
Eight equal drops of water are falling through air with a steady speed of \(10\,cm / s\). If the drops coalesce, the new velocity is \(.........\,cm/s\)
- A \(10\)
- B \(40\)
- C \(16\)
- D \(5\)
Answer & Solution
Correct Answer
(B) \(40\)
Step-by-step Solution
Detailed explanation
\(v \propto r ^2\) \(\frac{ v _1}{ v _2}=\left(\frac{ r }{ R }\right)^2\) \(8 \cdot \frac{4}{3} \pi r ^3=\frac{4}{3} \pi R ^3\) \(R =2 r\) \(\frac{10}{ v _2}=\left(\frac{1}{2}\right)^2\) \(v _2=40\,cm / s\)
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