Correct Answer - Option 1 : 1.13 × 10
-4 N
CONCEPT:
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Viscosity: The state of being sticky, thick, and semi-fluid inconsistency, due to internal friction of fluids is called viscosity.
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Stokes Law: This law tells about the viscous drag force when a sphere goes with a terminal velocity v inside a liquid.
By this law viscous drag force is given by
F = 6πηrv
where r is the radius of the sphere, v is the velocity, and η is the viscosity of the fluid.
CALCULATION:
Given that r = 2 mm = 2 × 10-3 m; v = 30 mm/s = 30 × 10-3 m/s; η = 1 N-s/m2
viscous drag force F = 6πηrv
F = 6π × 1 × 2 × 10-3 × 30 × 10-3
F = 36π × 10-6 N
F = 1.13 × 10-4 N
So the correct answer is option 1.