An air bubble of diameter 6 mm rises steadily through a of density 1750 kg/m³ at the rate of 0.35 cm/s. The co-efficient of viscosity of the (neglect density of air) is ___________ Pas (given, g = 10 ms⁻²). Numerical answer type. Work it out, then open the answer.

Answer: 10. Upthrust balances viscous drag: η = (2r²σ g)/(9v) r = 3 × 10⁻³ m, σ = 1750 kg/m³, v = 3.5 × 10⁻³ m/s η = 2 × 9 × 10⁻⁶ × 1750 × 109 × 3.5 × 10⁻³ = (0.315)/(0.0315) = 10 Pa s Coefficient of viscosity = 10 Pa s.

An air bubble of diameter 6 mm rises steadily through a of density… | JEE Main 2023 (8 Apr, Shift 1)

Q34JEE Main 2023 · 8 APR · SHIFT 1Medium

Terminal Velocity

An air bubble of diameter $6\text{ mm}$ rises steadily through a of density $1750\text{ kg/m}^{3}$ at the rate of $0.35\text{ cm/s}$ . The co-efficient of viscosity of the (neglect density of air) is ___________ Pas (given, $\mathrm{g} = 10\text{ ms}^{-2}$ ).

Numerical answer type. Work it out, then open the answer.

Show answer and solution

Answer: 10

Upthrust balances viscous drag: $\eta = \dfrac{2r^2\sigma g}{9v}$
$r = 3 \times 10^{-3}$ m, $\sigma = 1750\ \text{kg/m}^3$ , $v = 3.5 \times 10^{-3}$ m/s
$\eta = \dfrac{2 \times 9 \times 10^{-6} \times 1750 \times 10}{9 \times 3.5 \times 10^{-3}} = \dfrac{0.315}{0.0315} = 10$ Pa s
Coefficient of viscosity $= 10$ Pa s.

Report a mistake

Terminal Velocity question from JEE Main 2023 (8 Apr, Shift 1)

More questions on Terminal Velocity