Stoke’s Law

A spherical ball of radius $\text{1}\times 10^{-4} \mathrm{m}$ and density $104 \mathrm{kg} {\mathrm{m}}^{-3}$^​ falls freely under gravity through a distance $h$ before entering a tank of water. If after entering the water the velocity of the ball does not change, find $h$. The viscosity of water is $9.8\times 10^{-6} {\mathrm{Nsm}}^{-2}$.

A parachute descend slowly because it has a _____ surface area coming down fast.

 With the parachute out it adds more friction slowing him down because air resistance works against the very large surface area of the parachute.

Two identical balloons, filled with gases of different densities $0.9 \mathrm{kg} {\mathrm{m}}^{-3}$ and $1.1\mathrm{kg} {\mathrm{m}}^{-3}$ are released from an airplane into the atmosphere (density $=1 \mathrm{kg} {\mathrm{m}}^{-3}$ ). Find the speed of lighter balloon as seen by heavier balloon after a long time.

Given: radius of the balloons $r=3 \mathrm{cm}$
Coefficient of viscosity $\eta ={10}^{-5} \mathrm{Pa}-\mathrm{s}$
$g=10 {\mathrm{ms}}^{-2}$

Does a parachute descend slowly?

A raindrop falling in air is similar to motion of what kind of body in viscous medium?

A cylinder of mass $M$ and radius $R$ moves with constant speed $v$ through a region of space that contains dust particles of mass $m$ which are at rest. There are $n$ number of particles per unit volume. The cylinder moves in a direction perpendicular to its axis. Assume $m<<M$ and that the particles do not interact with each other. All the collisions taking place are perfectly elastic and the surface of the cylinder is smooth. The drag force per unit length of the cylinder required to maintain a speed $v$ constant for the cylinder when it has entered a region is $\frac{K}{3}nmR{v}^2$. Find the value of $K$.

A lead ball of $1 \mathrm{mm}$ diameter falls through a long column of glycerine. The variation of its velocity with distance covered is represented by

Eight identical drops of water, each of radius $2 \mathrm{mm}$ are falling through air at a terminal velocity of $8 \mathrm{cm} {\mathrm{s}}^{-1}$. If they coalesce to form a single drop, then the terminal velocity of the combined drop will be :

A spherical ball is dropped in a long column of viscous liquid. The acceleration of ball as a function of time may be best represented by the graph:-

Millikan's oil drop experiment is used to find:

Which of the following options is correct regarding the retarding viscous force acting on a spherical ball of radius $\mathrm{R}$  falling in a viscous liquid with a velocity $\mathrm{v}$ ?

Best graph from following between terminal velocity $\left(\mathrm{v}\right)$ of a spherical object and radius of object $\left(\mathrm{r}\right)$ is 

A drop of water of radius $0.0015 \mathrm{m}\mathrm{m}$ is falling in air. If the coefficient of viscosity of air is $2.0\times {10}^{-5} \mathrm{k}\mathrm{g}\mathrm{ }{\mathrm{m}}^{-1} {\mathrm{s}}^{-1}$, the terminal velocity of the drop will be: (The density of water $={10}^3 \mathrm{k}\mathrm{g}\mathrm{ }{\mathrm{m}}^{-3}$ and $\mathrm{g}=10 \mathrm{m}\mathrm{ }{\mathrm{s}}^{-2}$)

Eight drops of water, each of radius $2 \mathrm{m}\mathrm{m}$ are falling through air at a terminal velocity of $8 \mathrm{c}\mathrm{m}\mathrm{ }{\mathrm{s}}^{-1}$. If they coalesce to from a single drop, then the terminal velocity of combined drop will be:

A metallic sphere of mass $M$ falls through glycerine, If we drop a ball of mass$8M$ of same metal into a column of glycerine, the terminal velocity of the ball will be

A spherical ball of radius $\mathrm{R}$ is falling in a viscous fluid with velocity $\mathrm{v}$. The retarding viscous force acting on the spherical ball is:

A copper ball of radius $r$ is moving with a uniform velocity $v$ in the mustard oil and the dragging force acting on the ball is $F.$ The dragging force on the copper ball of radius $2r$ with uniform velocity $2v$ in the mustard oil is

A rain drop of radius $0.3 mm$ has a terminal velocity in air $1 m{s}^{-1}.$ The viscosity of air is $18\times {10}^{-5}$ poise. Find the viscous force on the rain drops.

What will be the approximate terminal velocity of a rain drop of diameter $1.8\times {10}^{-3}m$ , when density of rain water $\approx {10}^{3}kg{m}^{-3}$ and the coefficient of viscosity of air $\approx 1.8\times {10}^{-5}N-s{m}^{-2}$ ? $\left(\mathrm{N}\mathrm{e}\mathrm{g}\mathrm{l}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{ }\mathrm{b}\mathrm{u}\mathrm{o}\mathrm{y}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{y}\mathrm{ }\mathrm{o}\mathrm{f}\mathrm{ }\mathrm{a}\mathrm{i}\mathrm{r}\right)$