EASY

Earn 100

Draw labelled diagram to show angle of contact between mercury and clean glass.

Important Questions on Mechanical Properties of Fluids

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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

HARD

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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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MEDIUM

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

' M'

is the mass of water that rises in a capillary tube of radius

' r'

, then mass of water which will rise in a capillary tube of radius

' 2 r'

is:

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

Pressure inside two soap bubbles are

1.01

and

1.02

atmosphere, respectively. The ratio of their volumes is :

HARD

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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:

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

In a capillary tube having area of cross-section

A

, the water rises to a height

h

. If the cross-sectional area is reduced to

\frac{A}{9}

, the rise of water in the capillary tube is

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

Two mercury drops (each of radius

r

) merge to form a bigger drop. The surface energy of the bigger drop, if

T

is the surface tension, is

MEDIUM

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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

MEDIUM

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

A big water drop is formed by the combination of

n

small water drops of equal radii. The ratio of the surface energy of

n

drops to the surface energy of the big drop is

MEDIUM

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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.

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

If a soap bubble expands, the pressure inside the bubble

MEDIUM

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

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:

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

A soap bubble of radius

r

is blown up to form a bubble of radius

2 r

under isothermal conditions. If

σ

is the surface tension of the soap solution, the energy spent in the process is

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Surface Tension

A rectangular film of liquid is extended from

(4 cm \times 2 cm)

(5 cm \times 4 cm)

. If the work done is

3 \times 10^{- 4} J

, the value of the surface tension of the liquid is

Draw labelled diagram to show angle of contact between mercury and clean glass.

Important Questions on Mechanical Properties of Fluids

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