Spherical balls of radius $ 'r'$ are falling in a viscous fluid of viscosity '$\eta$' with a velocity $ 'v'. $ The retarding viscous force acting on the spherical ball is
AInversely proportional to $ 'r'$ but directly proportional to velocity $ 'v'$
BDirectly proportional to both radius $ 'r' $ and velocity $ 'v'$
CInversely proportional to both radius $ 'r' $ and velocity $ 'v'$
DDirectly proportional to $ 'r'$ but inversely proportional to $ 'v'$
AIEEE 2004, Easy
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BDirectly proportional to both radius $ 'r' $ and velocity $ 'v'$
b (b)$F = 6\,\pi \eta \,rv$
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