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Calculate the viscous force acting on a rain drop of diameter 1 mm, falling with a uniform velocity 2 m/s through air. The coefficient of viscosity of air is 1.8 $$\times$$ 10-5 Ns/m2

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Correct answer = 3.394 ×10-7 N or 3.393 ×10-7 N

Explaination::

Given: d= 1 mm, v= 2 m/s, η= 1.8 × 10-5 Ns/m2

r =d/2 =0.5 mm = 5 ×10-4 m,

Solution:

By Stoke’s law the viscous force on rain drop is

f= 6πηr v0

= 6 ×3.142 x 1.8 × 10-5 x 5 ×10-4 × 2

= 3.394 ×10-7 N

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