Fluid Mechanics Viscosity Question 301
Question: A container filled with viscous liquid is moving vertically downwards with constant speed$ 3v_{0} $ . At the instant shown, a sphere of radius r is moving vertically downwards (in liquid) has speed$ v_{0} $ . The coefficient of viscosity is$ \eta $ . There is no relative motion between the liquid and the container. Then at the shown instant, the magnitude of viscous force acting on sphere is
Options:
A) $ 6\pi \eta rv_{0} $
B) $ 12\pi \eta rv_{0} $
C) $ 18\pi \eta rv_{0} $
D) $ 24\pi \eta rv_{0} $
Show Answer
Answer:
Correct Answer: B
Solution:
[b] Relative to liquid, the velocity of sphere is $ 2v_{0} $ upwards. $ \therefore $ Viscous force on sphere $ =12\pi \eta ,rv_{0} $ downwards
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