Mechanical Properties of Fluids · Question 1

A spherical liquid drop of radius R acquires the terminal velocity v1 when falls through a gas of viscosity . Now the drop is broken into 64 identical droplets and each droplet acquires terminal velocity v2 falling through the same gas. The ratio of terminal velocities v1/v2 is .

1. 4
2. 0.25
3. 32
4. 16

A cylindrical vessel of 40 cm radius is completely filled with water and its capacity is 528 dm3 (dm : decimeter). The vessel is placed on a solid block of exactly same height as vessel. If a small hole is made at 70 cm below the top of water level, then horizontal range of water falling on the ground in the beginning is cm.

1. 120 2
2. 140 2
3. 140 3
4. 120 3

Eight mercury drops, each of radius r, coalesce to form a bigger drop. The surface energy released in this process is . (S is the surface tension of mercury).

1. 8 r2S
2. 16 r2S
3. 64 r2S
4. 4 r2S

The surface tension of a soap solution is 3.5 10-2 N/m. The work required to increase the radius of a soap bubble from 1 cm to 2 cm is 10-6 J. The value of is . ( =22/7)

A water spray gun is attached to a hose of cross sectional area 30 cm2. The gun comprises of 10 perforations each of cross sectional area of 15 mm2. If the water flows in the hose with the speed of 50 cm/s, calculate the speed at which the water flows out from each perforation. (Neglect any edge effects)

1. 100 m/s
2. 10 m/s
3. 1000 m/s
4. 15 102 m/s

A liquid drop of diameter 2 mm breaks into 512 droplets. The change in surface energy is 10-6 J. The value of is . (Take surface tension of liquid = 0.08 N/m)

1. 10
2. 7
3. 8
4. 11

A tub is filled with water and a wooden cube 10 cm 10 cm 10 cm is placed in the water. The wooden cube is found to float on the water with a part of it submerged in water. When a metal coin is placed on the wooden cube, the submerged part is increased by 3.87 cm. The mass of the metal coin is gram. (Take water density as 1 g/cm3 and density of wood as 0.4 g/cm3)

The surface tension of a soap bubble is 0.03 N/m. The work done in increasing the diameter of bubble from 2 cm to 6 cm is 10-4 J. The value of is . (Take =3.14)

1. 0.86
2. 0.64
3. 1.92
4. 7.68

If an air bubble of diameter 2 mm rises steadily through a liquid of density 2000 kg/m3 at a rate of 0.5 cm/s, then the coefficient of viscosity of liquid is Poise. (Take g=10 m/s2)

1. 0.88
2. 8.8
3. 88.8
4. 0.088

Sixty four raindrops of radius 1 mm each falling down with a terminal velocity of 10 cm/s coalesce to form a bigger drop. The terminal velocity of bigger drop is cm/s.