Water in river 20 m deep is flowing at a speed of $10 {\mathrm{m}\mathrm{s}}^{-1}$. The shearing stress between the horizontal layers of water in the river in ${\mathrm{N}\mathrm{ }\mathrm{m}}^{-2}$ is (coefficient of viscosity of water$={10}^{-3}$ SI units)

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 steel ball is dropped in a viscous liquid. The distance of the steel ball from the top of the liquid is shown below. The terminal velocity of the ball is closest to

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?