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NCERT Solutions for class 11 Physics | Chapter 10 - Mechanical Properties of Fluids

Questions
1 Streamline flow is more likely for liquids with
A high density
B high viscosity
C low density
D low viscosity

Answer:B, C
2 With increase in temperature, the viscosity of
A gases decreases
B liquids increases
C gases increases
D liquids decreases

Answer:C, D
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3 Pressure is a scalar quantity because
A it is the ratio of force to the area and both force and area are vectors
B it is the ratio of the magnitude of the force to area
C it is the ratio of a component of the force normal to the area
D it does not depend on the size of the area chosen

Answer:B, C
4 For a surface molecule
A the net force on it is zero
B there is a net downward force
C the potential energy is less than that of a molecule inside
D the potential energy is more than that of a molecule inside

Answer:B, D
5 The angle of contact at the interface of water-glass is 0°, ethyl alcohol-glass is 0°, mercury-glass is 140°, and methyl iodide-glass is 30°. A glass capillary is put in a trough containing one of these four liquids. It is observed that the meniscus is convex. The liquid in the trough is
A water
B ethyl alcohol
C mercury
D methyl iodide

Answer:mercury
6 An ideal fluid flows through a pipe of circular cross-section made of two sections with diameters 2.5 cm and 3.75 cm. The ratio of the velocities in the two pipes is
A 9:4
B 3:2
C √3: √2
D √2: √3

Answer:9:4
7 Along a streamline
A the velocity of a fluid particle remains constant
B the velocity of all fluid particles crossing a given position is constant
C the velocity of all fluid particles at a given instant is constant
D the speed of a fluid particle remains constant

Answer:the velocity of all fluid particles crossing a given position is constant
8 A tall cylinder is filled with viscous oil. A round pebble is dropped from the top with zero initial velocity. From the plot shown in the figure, indicate the one that represents the velocity (v) of the pebble as a function of time (t).

Mechanical Properties of Fluids

A (a)
B (b)
C (c)
D (d)

Answer:(c)
9 The angle of contact at the interface of water-glass is 0°, Ethyl Alcohol-glass is 0°, Mercury-glass is 140° and Methyl Iodide Glass is 30°. A glass capillary is put in a trough containing one of these four liquids. It is observed that the meniscus is convex. The liquid in the trough is
A water
B ethyl alcohol
C mercury
D methyl iodide.

Answer:mercury
10 When a soap bubble is charged
A It contracts
B It expands
C It does not undergo any change in size
D None of these

Answer:It expands
11 Water rises up to a height of 4 cm, in a capillary tube immersed vertically in water. What will be the length of water column in the capillary tube, if the tube is immersed in water, at an angle of 60o with the vertical?
A 4 cm
B 6 cm
C 8 cm
D 2 cm

Answer:8 cm
12 When there are no external forces, the shape of a liquid drop is determined by
A Surface tension of the liquid
B Density of liquid
C Viscosity of liquid
D Temperature of air only

Answer:Surface tension of the liquid
13 If common salt is dissolved in water, then the S.T. of salt water is
A Increased
B Decreased
C Not changed
D First decreases and then increases

Answer:Increased
14 Water rises to a height of 10 cm in a capillary tube, and mercury falls to a depth of 3.42 cm in the same capillary tube. If the density of mercury is 13.6 gm/cm3 and the angle of contact is 135o, the ratio of surface tension for water and mercury is
A 1:0.5
B 1:3
C 1:6.5
D 1.5:1

Answer:1:6.5
15 For tap water and clean glass, the angle of contact is
A 0°
B 90°
C 140°
D 8°

Answer:8°
16 Amount of energy required to blow a bubble of radius 5 cm, is (Surface tension of soap is 30 × 10-2 N/m)
A 1.88 J
B 1.88 × 10-1 J
C 1.88 × 10-2 J
D 1.88 × 10 J

Answer:1.88 × 10-2 J
17 The surface of water in contact with glass wall is
A Plane
B concave
C convex
D Both b and c

Answer:concave
18 The work done in blowing a soap bubble of radius R is W1 and that to a radius 3R is W2. the ratio of work done is
A 1:3
B 3:1
C 1:9
D 9:1

Answer:1:9
19 A liquid is kept in a glass vessel. If the liquid solid adhesive force between the liquid and the vessel is very weak as compared to the cohesive force in the liquid, then the shape of the liquid surface near the solid should be
A Concave
B Convex
C Horizontal
D Almost vertical

Answer:Convex
20 Two soap bubbles have radii in the ratio of 4:3. What is the ratio of work done to below these bubbles?
A 4:3
B 16:9
C 09:16
D 3:4

Answer:16:9

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