Question

If S identical rain drops each falling with terminal velocity v combine to form a big drop during their fall the terminal velocity of big drop formed is :

• A. v
• B. $\frac{v}{8}$
• C. 4v
• D. 2v

Answer 1

Answer: (C)

4v

$\begin{array}{c}v=\frac{2}{g}\frac{r^2\left(\delta -\sigma \right)}{\eta }\\ 8\times \frac{4}{3}\pi r^3=\frac{4}{3}\pi R^3\\ \Rightarrow R=2r\\ \Rightarrow v^{\prime }=4v\end{array}$

Hence,

option $\left(C\right)$ is correct answer.