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TS EAMCET · Physics · Mechanical Properties of Fluids

A rain drop of diameter 1 mm falls with a terminal velocity of \(0.7 \mathrm{~ms}^{-1}\) in air. If the coefficient of viscosity of air is \(2 \times 10^{-5} \mathrm{Pas}\), the viscous force on the rain drop is

  1. A \(13.2 \times 10^{-8} \mathrm{~N}\)
  2. B \(6.6 \times 10^{-8} \mathrm{~N}\)
  3. C \(26.4 \times 10^{-8} \mathrm{~N}\)
  4. D \(10.4 \times 10^{-8} \mathrm{~N}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(13.2 \times 10^{-8} \mathrm{~N}\)

Step-by-step Solution

Detailed explanation

\(F_v = 6 \pi \eta r v\) \(F_v = 6 \times 3.14159 \times (2 \times 10^{-5} \mathrm{Pas}) \times (0.5 \times 10^{-3} \mathrm{~m}) \times (0.7 \mathrm{~ms}^{-1})\) \(F_v = 13.1946 \times 10^{-8} \mathrm{~N}\) \(F_v \approx 13.2 \times 10^{-8} \mathrm{~N}\)
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