A small spherical solid ball is dropped in a viscous liquid. Its journey in the liquid is best described in the figure by :

1.  Curve A

2.  Curve B

3.  Curve C

4.  Curve D

Two drops of the same radius are falling through air with a steady velocity of 5 cm per sec. If the two drops coalesce, the terminal velocity would be 

1. 10 cm per sec                               
2. 2.5 cm per sec
3. $5\times (4{)}^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right.}$ cm per sec                       
4. $5\times \sqrt{2}$ cm per sec

Two equal drops of water each of radius r are falling through air with a steady velocity

of 8 cm/s . The two drops combine to form a big drop. The terminal velocity of big

drop will be 

(1) $8{\left(2\right)}^{\frac{2}{3}}<mspace\; width="1em"></mspace>cm/s<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>$

(2) $<mspace\; width="1em"></mspace>16{\left(2\right)}^{\frac{2}{3}}<mspace\; width="1em"></mspace>m<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>$

(3) $4{\left(2\right)}^{\frac{2}{3}}<mspace\; width="1em"></mspace>cm/s$

(4) 32 cm/s

A ball of mass m and radius r is released in a viscous liquid. The value of its terminal

velocity varies linearly with 

(1) 1/r only

(2) m/r  

(3) ${(m/r)}^{1/2}$

(4) m only 

If the terminal speed of a sphere of gold $(\mathrm{density}<mspace\; width="1em"></mspace>=<mspace\; width="1em"></mspace>19.5<mspace\; width="1em"></mspace>\mathrm{kg}/{\mathrm{m}}^3)$ is 0.2 m/s in a viscous liquid $(\mathrm{density}<mspace\; width="1em"></mspace>=<mspace\; width="1em"></mspace>1.5<mspace\; width="1em"></mspace>\mathrm{kg}/{\mathrm{m}}^3),$ find the terminal speed of a sphere of silver $(\mathrm{density}<mspace\; width="1em"></mspace>=<mspace\; width="1em"></mspace>10.5<mspace\; width="1em"></mspace>\mathrm{kg}/{\mathrm{m}}^3)$ of the same size in the same liquid

1.  0.4 m/s 

2.  0.133 m/s

3.  0.1 m/s 

4.  0.2 m/s