A spherical ball of density `rho` and radius` 0.003m` is dropped into a tube containing a viscous fluid up to the 0 cm mark as shown in the figure. Viscosity of the fluid `=1.26N-s//m^(2)` and its density `rho_(L)=(rho)/(2)=1260kg//m^(3)`. Assume that the ball reaches a terminal speed at 10cm mark. The time taken by the ball to travel the distance between the 10cm and 20cm mark is `(g=10m//s^(2))`

Options

A. 2s
B. 1s
C. 0.5s
D. 5s

Answer

D

Explanation

`v_(T)=2/9 (r^(2)(rho-sigma)g)/(eta)`
`=(2xx(0.003)^(2)(1260xx2-1260)xx10)/(9xx1.26)`
`=0.02 m//s`
`t=(d)/(v_T)=(10xx10^(-2))/(0.02)=5s`.