EASY

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What is the physical significance of angle of contact?

Important Questions on Mechanical Properties of Fluids

EASY

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

Identify the incorrect statement about 'angle of contact':
(a) Angle of contact depends upon the inclination of the solid surface to the liquid surface.
(b) If the angle of contact of a liquid and a solid surface is less than

90 °,

then the liquid spreads on the surface of the solid.
(c) Angle of contact increases with increase in temperature of liquid.
(d) The value of angle of contact for pure water and glass is zero.

MEDIUM

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

A soap bubble, blown by a mechanical pump at the mouth of a tube increases in volume with time at a constant rate. The graph that correctly depicts the time dependence of pressure inside the bubble is given by:

MEDIUM

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

A soap bubble of radius

3 cm

is formed inside another soap bubble of radius,

6 cm

. The radius of an equivalent soap bubble that has the same excess pressure as inside the smaller bubble with respect to the atmospheric pressure is____

cm .

EASY

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

Given below are two statements: One is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): Clothes containing oil or grease stains cannot be cleaned by water wash.

Reason (R): Because the angle of contact between the oil/grease and water is obtuse. In light of the above statements, choose the correct answer from the option given below.

EASY

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

Two separate soap bubbles of radii

3 \times 10^{- 3} m

and

2 \times 10^{- 3} m

respectively, formed of same liquid (surface tension

65 \times 10^{- 2} N m^{- 1}

) come together to form a double bubble. The radius of interface of double bubble is

EASY

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

If a soap bubble expands, the pressure inside the bubble

MEDIUM

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

A boy formed a bubble and a liquid drop form the same soapy water. The pressure difference between inside and outside of the soap bubble is measured to be

100 N / m^{2} .

If the radius of the droplet is half of the radius of the bubble, then the pressure difference between the inside and outside of the droplet is

HARD

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

Calculate the work done in increasing the radius of a soap bubble in air from 1 cm to 2 cm. The surface tension of the soap solution is 30 dyne/cm. $(π = 3.142)$

EASY

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

A soap bubble having radius of

1 m m

is blown from a detergent solution having a surface tension of

2.5 \times 10^{- 2} N m^{- 1} .

The pressure inside the bubble equals at a point

Z_{0}

below the free surface of water in a container. Taking

g = 10 m s^{- 2},

density of water

= 10^{3} k g m^{- 3},

the value of

Z_{0}

EASY

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

Pressure inside two soap bubbles are

1.01

and

1.02

atmosphere, respectively. The ratio of their volumes is :

MEDIUM

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

A spherical soap bubble of radius

3 cm

is formed inside another spherical soap bubble of radius

6 cm

. If the internal pressure of the smaller bubble of radius

3 cm

in the above system is equal to the internal pressure of the another single soap bubble of radius

r cm

. The value of

r

is _____

HARD

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

A small soap bubble of radius 4cm is trapped inside another bubble of radius 6cm without any contact. Let

P_{2}

be the pressure inside the inner bubble and

P_{0}

, the pressure outside the outer bubble. Radius of another bubble with pressure difference

P_{2} - P_{0}

between its inside and outside would be:

HARD

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

A bubble has surface tension

S

. The ideal gas inside the bubble has ratio of specific heats

γ = \frac{5}{3}

. The bubble is exposed to the atmosphere and it always retains its spherical shape. When the atmospheric pressure is

P_{a 1}

, the radius of the bubble is found to be

r_{1}

and the temperature of the enclosed gas is

T_{1}

. When the atmospheric pressure is

P_{a 2}

, the radius of the bubble and the temperature of the enclosed gas are

r_{2}

and

T_{2}

, respectively. Which of the following statement(s) is(are) correct?

EASY

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

A liquid will not wet the surface of a solid, if the angle of contact is

MEDIUM

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

An air bubble of radius

1 mm

is at a depth of

8 cm

below the free surface of a liquid column. If the surface tension and density of the liquid is

0.1 N m^{- 1}

and

2000 kg m^{- 3}

respectively, by what amount is the pressure inside the bubble greater than the atmospheric pressure?
(Take

g = 10 m s^{- 2}

)

HARD

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

Derive Laplace’s law for a spherical membrane.

MEDIUM

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

A large number of water drops, each of radius

r

, combine to have a drop of radius

R

. If the surface tension is

T

and mechanical equivalent of heat is

J

, the rise in heat energy per unit volume will be:

EASY

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

A glass capillary tube is of the shape of a truncated cone with an apex angle

α

so that its two ends have cross-sections of different radii. When dipped in water vertically, the water rises in it to a height

h

, where the radius of its cross-section is

b

. If the surface tension of water is

S

, its density is

ρ

, and its contact angle with glass is

θ

, then the value of

h

will be (

g

is the acceleration due to gravity)

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HARD

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

If two glass plates have water between them and are separated by very small distance (see figure), it is very difficult to pull them apart. It is because the water in between forms cylindrical surface on the side that gives rise to lower pressure in the water in comparison to atmosphere. If the radius of the cylindrical surface is R and surface tension of water is T then the pressure in water between the plates is lower by:

Question Image

MEDIUM

Physics>Mechanics>Mechanical Properties of Fluids>Angle of Contact

The excess pressure inside a spherical drop of water is four time that of another drop. Then their respective mass ratio is

What is the physical significance of angle of contact?

Important Questions on Mechanical Properties of Fluids

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