A spherical ball of density ρ and radius 3 mm is dropped into a tube containing a viscous liquid filled a upto 0 mark as shown in the figure. Viscosity of the liquid is 1.260 N−s/m2 and its density is ρL=ρ/2=1260kg/m3. Assume the ball reaches a terminal speed by the 10 cm mark. The time taken by the ball to travel the distance between the 10 cm and 20 cm mark is
(take g= 10 m/s2)