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NEET · Physics · STD 11 - 9.1 fluid mechanics

The terminal velocity of a copper ball of radius \(5\,mm\) falling through a tank of oil at room temperature is \(10\,cm\,s ^{-1}\). If the viscosity of oil at room temperature is \(0.9\,kg\,m ^{-1} s ^{-1}\), the viscous drag force is :

  1. A \(8.48 \times 10^{-3}\,N\)
  2. B \(8.48 \times 10^{-5}\,N\)
  3. C \(4.23 \times 10^{-3}\,N\)
  4. D \(4.23 \times 10^{-6}\,N\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(8.48 \times 10^{-3}\,N\)

Step-by-step Solution

Detailed explanation

\(F\,=6 \pi \eta rv\) \(\quad =6 \times 3.14 \times 0.9 \times 5 \times 10^{-3} \times 10 \times 10^{-2}\)
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