Viscosity, Stoke’s Law, Terminal Velocity (Board Level)

Q.1

Two drops of same radius are falling through air with steady velocity of v cm/s. If the two drops coalesce, what would be the terminal velocity?

(a) 4v               (b) (4)^1/3v              (c) 2v                  (d) 64v

Ans.  (b)

Q.2

When a tangential force of 0.02 N is applied on a large wooden plate of area 10 m² floating on the surface of the river, plate moves with the speed 2 m/s on the river surface. IF the river is 1 m deep and the water in contact with the bed is stationary, then coefficient of viscosity of water is

(a) 2 ´ 10^-2 poise                                

(b) 10^-3 poise

(c) 10^-4 poise                                      

(d) 2 ´ 10^-1 poise

Ans.  (b)

Q.3

From amongst the following curves, which one shows the v ariation of the velocity v with time t for a small sized spherical body falling vertically in a long column of viscous liquid.