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 $.........\,cm/s$
JEE MAIN 2023, Diffcult
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$v \propto r ^2$
$\frac{ v _1}{ v _2}=\left(\frac{ r }{ R }\right)^2$
$8 \cdot \frac{4}{3} \pi r ^3=\frac{4}{3} \pi R ^3$
$R =2 r$
$\frac{10}{ v _2}=\left(\frac{1}{2}\right)^2$
$v _2=40\,cm / s$
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