Mechanical Properties of Fluids · Question 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.

A cubical block of density b = 600 kg/m3 floats in a liquid of density l = 900 kg/m3. If the height of block is H = 8.0 cm, then height of the submerged part is cm.

1. 6.3
2. 4.3
3. 7.3
4. 5.3

A soap bubble of surface tension 0.04 N/m is blown to a diameter of 7 cm. If (15000 - x) of work is done in blowing it further to make its diameter 14 cm, then the value of x is . ( = 22/7)