Viscosity

Define coefficient of viscosity. Explain stokes' law and explain the conditions under which a raindrop attains terminal velocity $v_t$. Give the expression for $v_t$. 

"Terminal velocity is more if surface area of the body is more". Give reason in support of your answer.

When water flows through a pipe, which of the layers moves fastest and slowest?

Define viscosity. What are its units and dimensions?

In Millikan's oil drop experiment, what is the terminal speed of an uncharged drop of radius $2.0 \mathrm{x} {10}^{-5}$ m and density $1.2 \mathrm{x} {10}^{-3 }\mathrm{kg} {\mathrm{m}}^{-3}$. Take the viscosity of air at the temperature of the experiment to be $1.8 \times {10}^{-5 } \mathrm{Pa} \mathrm{s}$. How much is the viscous force on the drop at that speed? Neglect buoyancy of the drop due to air.

(a) What is the largest average velocity of blood flow in an artery of radius $2 \times {10}^{-3} \mathrm{m}$ if the flow must remain laminar? (Take density of blood to be $1.06 \times {10}^3 \raisebox{1ex}{$\mathrm{kg}$}\!\left/ \!\raisebox{-1ex}{${\mathrm{m}}^3$}\right.$)
(b) What is the corresponding flow rate? (Take viscosity of blood to be $2.084 \times {10}^{-3} \mathrm{Pa} \mathrm{s}$).