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JEE Main 202127 AugustMorning Shift
Exam
JEE Main
Year
2021
Date
27 August
Shift
Morning Shift
Subject
Physics
Chapter
Mechanical Properties of Fluids

JEE Main 2021 · 27 August · Morning Shift · Physics · Mechanical Properties of Fluids

In Millikan's oil drop experiment, what is viscous force acting on...

In Millikan's oil drop experiment, what is viscous force acting on an uncharged drop of radius 2.0×10−5m2 . 0 \times {10}^{- 5}m and density 1.2×103kgm−31 . 2 \times {10}^{3}kg{m}^{- 3}? Take viscosity of liquid =1.8×10−5Nsm−2.= 1 . 8 \times {10}^{- 5}Ns{m}^{- 2} . (Neglect buoyancy due to air).

Options

  1. A5.8×10−10N5 . 8 \times {10}^{- 10}N
  2. B3.9×10−10N3 . 9 \times {10}^{- 10}N
  3. C1.8×10−10N1 . 8 \times {10}^{- 10}N
  4. D3.8×10−11N3 . 8 \times {10}^{- 11}N

Correct answer

B. 3.9×10−10N3 . 9 \times {10}^{- 10}N

Step-by-step solution

Use the concept the viscous force is the same as the weight of the body,

⇒F=mg=ρ×(43πr3)×g=3.9×10−10N⇒ F = mg = ρ \times \left(\dfrac{4}{3}\pi{r}^{3}\right) \times g = 3 . 9 \times {10}^{- 10}N.

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