J J Science Academy

1. A ball rises to the surface of a liquid with constant velocity. The density of the liquid is four times the density of the material of the ball. The frictional force of the liquid on the rising ball is greater than the weight of the ball by a factor of

1) 22) 33) 3}4) 6

2. A spherical ball falls through a viscous medium with terminal velocity v. If this ball were replaced by another ball of the same mass but half the radius, then the terminal velocity will be [Neglect the effect of buoyancy]

1) v2) $2 v$3) $4 v$4) $8 v$

3. The terminal velocity of a sphere, of radius R , moving through a viscous medium is proportional to the volume of the sphere as $v \propto V^x$. The $x=$

1) $\frac{1}{3}$2) $\frac{2}{3}$3) $\frac{4}{3}$4) 2

4. A metal sphere is dropped in a long jar containing viscous fluid. The velocity-time graph is

1)

2)

3)

4)

5. In the graph of drag force against time is

1)

2)

3)

4)

6. In the graph of net force against time is

1)

2)

3)

4)

7. If the terminal speed of a sphere of gold (density $=19.5 kg / m^3$ ) is $0.2 m / s$ in viscous liquid (density = $1.5 kg / m^3$ ), the terminal speed of a sphere of silver (density = $10.5 kg / m^3$ ) of the same size in the same liquid, is

1) $0.4 m / s$2) $0.133 m / s$3) $0.1 m / s$4) $0.2 m / s$

8. The terminal velocity $V_t$ and coefficient of viscosity $\eta$ of a liquid are related as

1) $V_t \propto \eta$2) $V_t \propto \frac{1}{\eta}$3) $V_t \propto \frac{1}{\eta^2}$4) $V_t \propto \frac{1}{\eta^4}$

9. Terminal velocity of a body with radius r is directly proportional to

1) r }\\mp@subsup{}{}{12) $r^{-2}$3) $r^{-1}$4) $r^{+2}$

10. The ratio of radii of two spherical drops is $1: 2$. The ratio of terminal velocities of these drops will be

1) $4: 1$2) $1: 2$3) $2: 1$4) $1: 4$

11. If the terminal speed of a sphere of gold (density $=19.5 kg / m^3$ ) is $0.2 m / s$ in a viscous liquid (density = $1.5 kg / m^3$ ), the terminal speed of a sphere of silver (density = $10.5 kg / m^3$ ) of the same size in the same liquid

1) $0.2 m / s$2) $0.4 m / s$3) $0.133 m / s$4) $0.1 m / s$

12. A body of density $D_1$ and mass $M$ is moving downwards in glycerine of density $D_2$. What is the viscous force acting on it?

1) $M g(1-\frac{D_2}{D_1})$2) $M g(1-\frac{D_1}{D_2})$3) $MgD_1$4) $MgD_2$

13. A small metal ball of mass ' $m$ ' is dropped in a liquid contained in a vessel, attains a terminal velocity ' $v$ '. If a metal ball of same material but of mass ' $8 m$ ' is dropped in same liquid then the terminal velocity will be

1) v2) 2v3) 4 v4) 8 v

14. A ball of mass $m$ and radius $r$ is dropped in a liquid. Its terminal velocity is directly proportional to

1) 1/r2) m/r3) $\sqrt{m / r}$4) m

15. A small metal sphere of radius a is falling with a velocity v through a vertical column of a viscous liquid. If the coefficient of viscosity of the liquid is $\eta$, then the sphere encounters an opposing force of

1) 6 $\pi$$\eta$a2v2) $\frac{6 \eta v}{\pi a}$3) $6 \pi \eta a v$4) $\frac{\pi \eta v}{6 a^3}$

16. The velocity of falling rain drops attains limited value because of .

1) Surface tension2) Upthrust due to air3) Viscous force exerted by air4) Air current