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JEE Main 2026 (2 Apr, Shift 2) · Terminal Velocity

Terminal Velocity question from JEE Main 2026 (2 Apr, Shift 2)

Q14JEE Main 2026 · 2 APR · SHIFT 2Medium

Terminal Velocity

If an air bubble of diameter 2 mm rises steadily through a liquid of density 2000 kg/m3 at a rate of 0.5 cm/s, then the coefficient of viscosity of liquid is ______ Poise. (Take g = 10 m/s2)

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Answer: (b)

  1. For a rising bubble (air density neglected): η=2r2σg9v\eta = \dfrac{2r^2\sigma g}{9v}
  2. r=10−3r = 10^{-3} m, σ=2000 kg/m3\sigma = 2000\ \text{kg/m}^3, v=5×10−3v = 5 \times 10^{-3} m/s
  3. η=2×10−6×2000×109×5×10−3=0.040.045≈0.889\eta = \dfrac{2 \times 10^{-6} \times 2000 \times 10}{9 \times 5 \times 10^{-3}} = \dfrac{0.04}{0.045} \approx 0.889 Pa s =8.89= 8.89 Poise
  4. So the answer is (b) 8.8.
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