Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NEET
Exam
NEET
Subject
Physics
Chapter
Mechanical Properties of Fluids

NEET · Physics · Mechanical Properties of Fluids

A small glass marble of radius 2 ~mm falls with a constant velocity...

A small glass marble of radius 2 mm2 \mathrm{~mm} falls with a constant velocity of 5 cm s−15 \mathrm{~cm} \mathrm{~s}^{-1} through a tall cylinder filled with a liquid. If the viscous drag force acting on the marble is 3.768×10−3 N3.768 \times 10^{-3} \mathrm{~N}, the coefficient of viscosity of the liquid is: (Take π=3.14\pi = 3.14)

Options

  1. A2.0×10−3 Pa⋅s2.0 \times 10^{-3} \mathrm{~Pa}\cdot\mathrm{s}
  2. B2.0×10−2 Pa⋅s2.0 \times 10^{-2} \mathrm{~Pa}\cdot\mathrm{s}
  3. C37.68 Pa⋅s37.68 \mathrm{~Pa}\cdot\mathrm{s}
  4. D2.0 Pa⋅s2.0 \mathrm{~Pa}\cdot\mathrm{s}

Correct answer

D. 2.0 Pa⋅s2.0 \mathrm{~Pa}\cdot\mathrm{s}

Step-by-step solution

According to Stokes' law, the viscous drag force is given by:
F=6πηrv\mathrm{F} = 6 \pi \eta r v

Rearranging the formula to solve for the coefficient of viscosity η\eta:
η=F6πrv\eta = \dfrac{\mathrm{F}}{6 \pi r v}

Given values:
F=3.768×10−3 N\mathrm{F} = 3.768 \times 10^{-3} \mathrm{~N}
r=2 mm=2×10−3 mr = 2 \mathrm{~mm} = 2 \times 10^{-3} \mathrm{~m}
v=5 cm s−1=5×10−2 m s−1v = 5 \mathrm{~cm} \mathrm{~s}^{-1} = 5 \times 10^{-2} \mathrm{~m} \mathrm{~s}^{-1}

Substituting the values:
η=3.768×10−36×3.14×2×10−3×5×10−2\eta = \dfrac{3.768 \times 10^{-3}}{6 \times 3.14 \times 2 \times 10^{-3} \times 5 \times 10^{-2}}

η=3.768×10−318.84×10×10−5\eta = \dfrac{3.768 \times 10^{-3}}{18.84 \times 10 \times 10^{-5}}

η=3.768×10−31.884×10−3\eta = \dfrac{3.768 \times 10^{-3}}{1.884 \times 10^{-3}}

η=2.0 Pa⋅s\eta = 2.0 \mathrm{~Pa}\cdot\mathrm{s}

Answer: 2.0 Pa⋅s2.0 \mathrm{~Pa}\cdot\mathrm{s}
Practice Mechanical Properties of Fluids on Quantrex Academy →

More from Mechanical Properties of Fluids

In the measurement of viscosity of liquids using terminal velocity experiment, spherical… NEET 2026A submarine is designed to withstand an absolute pressure of 100 atm. How deep can it go… NEET 2026Water flows in a streamline motion through a horizontal pipe of circular cross-section as… NEET 2026Consider a water tank shown in the figure. It has one wall at x=L and can be taken to be… NEET 2025A thin flat circular disc of radius 4.5 cm is placed gently over the surface of water. If… NEET 2024An ideal fluid is flowing in a non-uniform cross-sectional tube X Y (as shown in the… NEET 2024The amount of energy required to form a soap bubble of radius 2cm from a soap solution is… NEET 2023The viscous drag acting on a metal sphere of diameter 1 ~mm , falling through a fluid of… NEET 2023 Full Mechanical Properties of Fluids list All NEET PYQs