Surface Tension

Q. The wettability of a surface by a liquid depends primarily on:

1. Viscosity
2. Surface tension
3. Density
4. Angle of contact between the surface and the liquid

Q. Explain why (a) The angle of contact of mercury with glass is obtuse, while that of water with glass is acute. (b) Water on a clean glass surface tends to spread out while mercury on the same surface tends to form drops. (Put differently, water wets glass while mercury does not.) (c) Surface tension of a liquid is independent of the area of the surface (d) Water with detergent disolved in it should have small angles of contact. (e) A drop of liquid under no external forces is always spherical in shape

Q.

A liquid is contained in a vertical tube of semicircular cross section. The contact angle is zero. The forces of surface tension on the curved part and on the flat part are in ratio.

1. 1:1

2. 1:2

3. 2:π

4. π:2

Q. Pressure inside two soap bubbles are 1.02 atm and 1.05 atm respectively. the ratio of their surface area is

Q. A drop of liquid of density ρ is floating half immersed in a liquid of density σ. If s is the surface tension, then diameter of the drop of liquid is

Q. The radius of a soap bubble is r and the surfacetension of soap solution is T. Keeping thetemperature constant, the extra energy needed todouble the radius of the soap bubble by blowing, is(1) 16 ㎡T(3) 8 TT(2) 32 ㎡T(4) 24 ㎡T

Q.

Surface tension is due to

1. Frictional forces between molecules

2. Cohesive forces between molecules

3. Adhesive forces between molecules

4. Gravitational forces

Q.

Venturimeter is a device used to measure the

1. Rate of expansion of an ideal gas

2. Rate of flow of a compressible liquid

3. Rate of expansion of a real gas

4. Rate of flow of an incompressible liquid

Q.

The meniscus of mercury in the capillary tube is

1. Plane

2. Concave

3. Uncertain

4. Convex

Q.

Air is pushed into a soap bubble of radius 'r' to double its radius. If the surface tension of the soap solution is S, the work done in the process is?

1. 16 π r² S

2. 24 π r² S

3. 8 π r² S

4. 12 π r² S

Q.

The amount of work done in blowing a soap bubble such that its diameter increases from d to D is (T= surface tension of the solution)

1. 

2. 

3. 

4. 

Q. Fill in the blanks using the word(s) from the list appended with each statement: (a) Surface tension of liquids generally . . . with temperatures (increases / decreases) (b) Viscosity of gases . . . with temperature, whereas viscosity of liquids . . . with temperature (increases / decreases) (c) For solids with elastic modulus of rigidity, the shearing force is proportional to . . . , while for fluids it is proportional to . .. (shear strain / rate of shear strain) (d) For a fluid in a steady flow, the increase in flow speed at a constriction follows (conservation of mass / Bernoulli’s principle) (e) For the model of a plane in a wind tunnel, turbulence occurs at a ... speed for turbulence for an actual plane (greater / smaller)

Q.

Radius of a soap bubble is r, surface tension of soap solution is T. Then without increasing the temperature, how much energy will be needed to double its radius

1. 

2. 

3. 

4. 

Q.

If two soap bubbles of different radii are connected by a tube,

1. air flows from bigger bubble to the smaller bubble till the sizes become equal

2. air flows from bigger bubble to the smaller bubble till the sizes are interchanged

3. air flows the smaller bubble to the bigger

4. there is no flow of air

Q. each molecule of a gas has f degree of freedom.the ratio Cp/Cv=gamma for the gas is

Q.

Two capillaries made of same material but of different radii are dipped in a liquid. The rise of liquid in one capillary is 2.2 cm and that in the other is 6.6 cm. The ratio of their radii is

1. 9 : 1

2. 1 : 9

3. 3 : 1

4. 1 : 3

Q. Two soap bubble coalesce to form one bubble . If decrease in volume and surface area are V and S respectively . Atmospheric pressure is P0 and surface tension is T, then correct relation is 3P0V+TS=0 P0V+TS=0 3P0V+4TS=0 None of these

Q. 14. When an air bubble of radius rrises from the bottom to the surfaceof a lake, its radius becomes 5r/4.Pressure of the atmosphere is equalto the 10 m height of water column.If the temperature is constant andthe surface tension is neglected, thedepth of the lake is

Q.

Rate of change of weight near the earth's surface varies with height (h) as

1. h^-1

2. h^1/2

3. h

4. h⁰

Q. The interatomic forces in solids are both attractive and repulsive.Explain the reason

Q.

Water rises in a capillary tube when its one end is dipped vertically in it, is 3 cm. If the surface tension of water is $75\times {10}^{-3}$ N/m, then the diameter of capillary will be

1. 0.1 mm

2. 0.5 mm

3. 1.0 mm

4. 2.0 mm

Q. if the angle of contact is less than 90degree the pressure just inside the surface of a meniscus (a)is less than atmospheric pressure (b)more than atm. pressure (c)same as atm.pressure (d)none of the above

Q.

What is the shape when a non-wetting liquid is placed in a capillary tube

1. Concave upward

2. Convex upward

3. Concave downward

4. Convex downward

Q. AllMS 2015 A sphere of radius 25 cm and mass 1 kg is hung by a string of negligible mass and length 40 cm, then tension in the string is:- (1) 10.81 N (2) 18.4 N R (3) 10 N (4) 8 N

Q. Whether air bubble in water and soap bubble in water has same excess pressure??

Q. a very long cylindrical shaped soap bubble in air has radius r. calculate the excess pressure inside the bubble. ( Surface tension of soap solution=S)

Q. For a liquid and glass interface , if adhesive force is greater than cohesive force , then the angle of contact is 1) greater than 90 2)equal to 90 3)less than 90 4) both 1 and

Q.

A glass plate is partly dipped vertically in the mercury and the angle of contact is measured. If the plate is inclined, then the angle of contact will

1. Increase

2. Remain unchanged

3. Decrease

4. Increase or decrease

Q. Two soap bubbles each of radius r are touching each other. The raditus of curvature of the common surfecewill be:

Q.

At what speed the velocity head of water is equal to pressure head of 40 cm of mercury?