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MHT CET · Physics · Mechanical Properties of Fluids

' n ' small water drops of same size (radius r ) fall through air with constant velocity V. They coalesce to form a big drop of radius R. The terminal velocity of the big drop is

  1. A \(\frac{\mathrm{VR}^2}{\mathrm{r}^2}\)
  2. B \(\frac{\mathrm{Vr}^2}{\mathrm{R}^2}\)
  3. C \(\frac{\mathrm{VR}}{\mathrm{r}}\)
  4. D \(\frac{\mathrm{Vr}}{\mathrm{R}}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\frac{\mathrm{VR}^2}{\mathrm{r}^2}\)

Step-by-step Solution

Detailed explanation

\(n \cdot \frac{4}{3}\pi r^3 = \frac{4}{3}\pi R^3 \Rightarrow R^3 = n r^3\) Terminal velocity \(V_t \propto r^2\)