Poise is the unit of

A small spherical body of radius $r$ and density $\rho$ moves with the terminal velocity $v$ in a fluid of coefficient of viscosity $\eta$ and density $\sigma .$ What will be the net force on the body?

A flat plate of area $10{ \mathrm{cm}}^2$ is separated form a large plate by a layer of Glycerine $1 \mathrm{mm}$ thick. If the coefficient of viscosity of Glycerine is $20$ poise, the force required to keep the plate moving with a velocity of $1 \mathrm{cm} {\mathrm{s}}^{-1}$ is $\underline{ }$
 

A water drop of radius $1\mu \mathrm{m}$ falls in a situation where the effect of buoyant force is negligible. Co-efficient of viscosity of air is $1.8\times {10}^{-5} \mathrm{N} \mathrm{s} {\mathrm{m}}^{-2}$ and its density is negligible as compared to that of water ${10}^6 \mathrm{g} {\mathrm{m}}^{-3}$. Terminal velocity of the water drop is

(Take acceleration due to gravity $=10{ \mathrm{m} \mathrm{s}}^{-2}$)

A spherical ball is dropped in a long column of a highly viscous liquid. The curve in the graph shown, which represents the speed of the ball $\left(v\right)$ as a function of time $\left(t\right)$ is