# MCQ Questions for Class 11 Physics Chapter 10 Mechanical Properties of Fluids with Answers

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## Mechanical Properties of Fluids Class 11 MCQs Questions with Answers

Multiple Choice Type Questions

Question 1.
An ice cube contains a large air bubble. The cube is floating on the surface of water contained in a trough. What will happen to the water level, when the cube melts?
(a) It will rise.
(b) It will fall.
(c) First it will fall then rise
(d) It will remain unchanged.

Answer: (d) It will remain unchanged.

Question 2.
A person is carrying a bucket in one hand and a fish in the other. If he puts fish in the’bucket, how will the load carried by the person change?
(a) It will be less.
(b) It will be more.
(c) No change.
(d) It will depend on the mass of the fish.

Question 3.
For a floating body to be in stable equilibrium, where should its centre of buoyancy be located?
(a) At the centre of gravity.
(b) Above the centre of gravity.
(c) Below the centre of gravity.
(d) It may be anywhere.

Answer: (b) Above the centre of gravity.

Question 4.
Why the aeroplanes are made to run on the runway before take off?
(а) It decreases the friction.
(b) It decreases atmospheric pressure.
(c) It decreases viscous drag of the air.
(d) It provides required lift to the aeroplane.

Answer: (d) It provides required lift to the aeroplane.

Question 5.
When the temperature of a liquid increases, its surface tension
(a) increases.
(b) decreases.
(c) remains unchanged.
(d) none of the above.

Question 6.
Insects are able to run on the surface of water because
(a) surface tension makes its surface to behave as an elastic membrane.
(b) insects swim on water.
(c) insects have less weight.
(d) of Archimede’s upthrust.

Answer: (a) surface tension makes its surface to behave as an elastic membrane.

Question 7.
A drop of water is broken into two drops. The sum of which property of the two drops is equal to that of the single one?
(b) surface area
(c) surface energy
(d) volume

Question 8.
Two drops of a liquid merge to form a single drop. In this process energy is
(a) absorbed.
(b) released.
(c) may be absorbed or released depending on the specific heat of the liquid.
(d) neither absorbed nor released.

Question 9.
What makes it difficult to separate two glass sheets having a drop of water between them?
(a) surface tension
(b) viscosity
(c) gravity
(d) atmospheric pressure

Question 10.
The addition of soap changes the surface tension of water to T1 and that of sugar changes it to T2. Thus
(a) T1 = T2
(b) T1 > T2
(c) T1 < T2
(d) None of the above

Question 11.
Water rises ill a capillary tube to a height of h. If the area of cross-section of the tube is made one-fourth, then the water will rise to a height of:
(a) h
(b) $$\frac {h}{2}$$
(c) 2h
(d) 4h

Question 12.
A liquid is flowing uniformly. The net external force causing the liquid to flow is
(a) less than viscosity.
(b) more than viscosity.
(c) equal to viscosity.
(d) not related to viscosity.

Question 13.
The maximum velocity of the liquid upto which the flow is streamlined does not depend upon
(b) pressure of the liquid.
(c) density of the liquid.
(d) viscosity of the liquid.

Answer: (b) pressure of the liquid.

Question 14.
The velocity upto which the flow of a liquid remains streamlined and above which it becomes turbulent is called
(a) critical velocity.
(b) terminal velocity.
(d) none of the above.

Question 15.
One of the major factors that determines the laminar (streamlined) Or turbulent nature of flow of the liquid is
(a) velocity of flow.
(b) pressure of the liquid.
(c) length of the path.
(d) surface tension.

Question 16.
The viscous force does not depend upon
(a) velocity.
(c) nature of the liquid.
(d) area.

Question 17.
In streamlined flow, the velocity of the liquid in contact with the containing vessel is
(a) zero.
(b) minimum but not zero.
(c) infinite.
(d) large.

Question 18.
A steadily flowing liquid enters a wide tube and continues to flow steadily. What will be the nature of the tube of flow in the widened part?
(a) widened.
(b) crowded.
(c) will remain as before.
(d) may be crowded or widened.

Question 19.
A body is falling freely in a viscous liquid. Finally it:
(a) falls with a constant velocity.
(b) falls with decreasing velocity.
(c) falls with increasing velocity.
(d) comes to rest in the liquid.

Answer: (a) falls with a constant velocity.

Question 20.
Hot syrup flows faster because its
(a) surface tension increases
(b) surface tension decreases
(c) viscosity decreases
(d) viscosity increases

Question 21.
To which type of the fluid is Bernoulli’s theorem strictly applicable?
(a) Viscous
(b) Anisotropic
(c) Compressible
(d) None of the above

Answer: (d) None of the above

Question 22.
Hydraulic brakes work on the basis of:
(a) Poiseuille’s law.
(b) Pascal’s law.
(c) Archemede’s principle.
(d) Bernoulli’s principle.

Question 23.
Sudden fall in the atmospheric pressure by a large amount shows
(a) rain
(b) fair weather
(c) cloud wave
(d) storm

Question 24.
If two liquids of mass m1 of density ρ1 and of mass m2 of density ρ2 are mixed, then the density of the mixture will be
(a) $$\frac {m_1ρ_1+m_2ρ_2}{m_1+m_2}$$
(b) $$\frac {(m_1+m_2)ρ_1ρ_2}{m_1ρ_2+m_2ρ_1}$$
(c) $$\frac {ρ_1+ρ_2}{2}$$
(d) $$\frac {m_1ρ_1+m_2ρ_2}{m_1ρ_1+m_2ρ_2}$$

Answer: (b) $$\frac {(m_1+m_2)ρ_1ρ_2}{m_1ρ_2+m_2ρ_1}$$

Question 25.
If two pieces of metal when immersed in a liquid have equal upthrust on them, then both pieces have equal
(a) mass
(b) density
(c) volume
(d) weight

Fill in the blanks

Question 1.
Work done in blowing a soap bubble of radius r and surface tension T is ……………..

Question 2.
The phenomenon of …………….. is used in the manufacture of lead shots.

Question 3.
The rise of liquid due to surface tension in a narrow capillary tube of diameter d is h. If the diameter is reduced to $$\frac {d}{2}$$, the rise will be ………………..

Question 4.
The surface tension of a liquid ……………….. with temperature.

Question 5.
The group of steamlines is called ………………..

Question 6.
The tube of flow is wide in the ……………….. of the tube.

Question 7.
Equal masses of two liquids of densities p1 and p2 are mixed, then the density of the mixture is ……………….. of their densities.

Question 8.
Two air bubbles existing in water close to each other will ………………..

Question 9.
Bernoulli’s Theorem is based on the conservation of ……………….. and is used in ………………..

Question 10.
A gale blows over a house. The force due to the gale on the roof is in the ………………..

Question 11.
In order that a floating body be in a stable equilibrium, its centre of buoyancy should be ………………..

Answer: vertically above its centre of gravity.

Question 12.
An atmosphere is the unit of ………………..

Question 13.
A body floats in a liquid contained in a beaker. The whole system falls under gravity. The upthrust on the body due to the liquid is ………………..

Question 14.
When stirring of a liquid is stopped, the liquid comes to rest due to ………………..

True/False Type Questions

1. Tell which one of the following statement is True/False?
(a) Broad handles provided with bags and suitcases reduce the pressure on the hand.
(b) A large pressure is produced by making pointed ends of the pins that decreases the area of contact between the pin and the given surface.
(c) Pressure on the ground is reduced by laying railway tracks on large-sized wooden or iron sleepers that in turn spread the weight of the train over a much larger area.

(a) True
(b) True
(c) True

2. Tell which one of the following statement is True/False?
(a) Pascal is the S.I. unit of pressure.
(b) For a liquid to be in equilibrium, the forces on it always act perpendicular to its surface.
(c) According to Pascal’s law, pressure is transmitted equally in all directions.
(d) The atmospheric pressure on earth’s surface comes to be about 1.013 × 105 Nm-2.

(a) True
(b) True
(a) True
(b) True

3. Tell which one of the following statement is True/False?
(a) The tendency of the fluid to apply an upward thrust on a body dipped in it is called buoyancy.
(b) The upward thrust is called buoyant force.
(c) If the weight of the liquid displaced is more than the weight of the body, then it sinks.

(a) True
(b) True
(c) False

4. Tell which one of the following statement is True/False?
(a) Things are cooked earlier inside a pressure cooker due to increase in the boiling point.
(b) Boiling point is raised if pressure is increased.
(c) The internal friction between the layers of the fluids is called viscosity.

(a) True
(b) True
(c) True

5. Which one of the following statement is True/False?
(a) A spherical body acquires terminal velocity in the vertically downward direction if its density is more than the density of the fluid.
(b) Both friction and viscosity are due to molecular attractions.
(c) Both coefficient of friction and coefficient of viscosity have no unit.

(a) True
(b) True
(c) False

6. Tell which one of the following statement is True/False?
(a) Reynold’s number helps us to distinguish the nature of flow of a fluid.
(b) Maximum velocity upto which the flow is streamlined is called critical velocity.
(c) Deep water always runs slow.

(a) True
(b) True
(c) True

7. Tell which of the following statement is True/False?
(a) A man is sitting in a boat which is floating on a point If the man drinks some water from the pond, then level of water decreases.
(b) Bernoulli’s Theorem is based on the conservation of energy.
(c) When stirring of a liquid is stopped, then it comes to rest due to surface tenstion.

(a) False
(b) True
(c) False

8. Mark True/False statement?
(a) It is easier to swim in sea water as the density of sea water is more than the density of ordinary water.
(b) Oil rises up iii the wick of a lamp due to its surface tension.
(c) A ship floating in sea water, sinks further on entering into fresh water in a river.

(a) True
(b) True
(c) True

9. Tell which one of the following statement is True/False?
(a) The angle of contact increases with the increase in temperature.
(b) Surface tension of boiling water is zero.
(c) A sheet can be made water proof by coating it with a substance which changes the angle of contact from acute to obtuse.

(a) True
(b) True
(c) True

10. Tell which one of the following statement is True/False?
(a) The soap film tends to shrinkto as small surface area as possible.
(b) Soap film consists of two surface layers.
(c) Pressure of air enclosed by the soap film is more than the atmospheric pressure.
(d) Pressure of air enclosed by the soap film is same as that of the atmosphere outside it.

(a) True
(b) True
(c) True
(d) False

Match Type Questions

 Column I Column II (a) Surface Tension (i) makes the liquid drops spherical (b) Adhesion (ii) help liquids to rise in a capillary tube (c) Molecular force (iii) helps us to write on the black-board with chalk (d) Cohesion (iv) helps us in soldering

 Column I Column II (a) Surface Tension (iv) helps us in soldering (b) Adhesion (iii) helps us to write on the black-board with chalk (c) Molecular force (ii) help liquids to rise in a capillary tube (d) Cohesion (i) makes the liquid drops spherical

 Column I Column II (a) Cohesion (i) flatens the large sized liquid drops (b) Surface tension (ii) causes surface tension (c) Gravity (iii) causes hairs of shaving brush to cling together

 Column I Column II (a) Cohesion (ii) causes surface tension (b) Surface tension (iii) causes hairs of shaving brush to cling together (c) Gravity (i) flatens the large sized liquid drops

 Column I Column II (a) Surface tension of water (i) as it reduces the surface tension (b) In a gravity free space (ii) helps an iron needle to float on its surface (c) Soap helps in the cleaning of clothes (iii) the liquid in a capillary tube rises to infinite height

 Column I Column II (a) Surface tension of water (ii) helps an iron needle to float on its surface (b) In a gravity free space (iii) the liquid in a capillary tube rises to infinite height (c) Soap helps in the cleaning of clothes (i) as it reduces the surface tension

 Column I Column II (a) Rain drops fall with   constant velocity due to (i) low density (b) Clouds float in air due to (ii) viscous fluids (c) Stoke’s theorem is applicable only to (iii) viscosity

 Column I Column II (a) Rain drops fall with   constant velocity due to (iii) viscosity (b) Clouds float in air due to (i) low density (c) Stoke’s theorem is applicable only to (ii) viscous fluids

 Column I Column II (a) Pressure (i) newton (b) Surface tension (ii) decapoise (c) Coefficient of viscosity (iii) Nn-1 (d) Viscous drag (iv) Nm-1 or Pa

 Column I Column II (a) Pressure (iv) Nm-1 or Pa (b) Surface tension (iii) Nn-1 (c) Coefficient of viscosity (ii) decapoise (d) Viscous drag (i) newton

 Column I Column II (a) Pressure (i) [ML1T-2] (b) Surface tension (ii) [ML-1rT-1] (c) Coefficient of viscosity (iii) [ML°T-2] (d) Viscous force (iv) [ML-1T-2]

 Column I Column II (a) Pressure (iv) [ML-1T-2] (b) Surface tension (iii) [ML°T-2] (c) Coefficient of viscosity (ii) [ML-1rT-1] (d) Viscous force (i) [ML1T-2]

 Column I Column II (a) Laminar flow (i) Rc > 3000 (b) Unstable flow (ii) 2000 < Rc < 3000 (c) Turbulent (iii) Rc < 2000

 Column I Column II (a) Laminar flow (iii) Rc < 2000 (b) Unstable flow (ii) 2000 < Rc < 3000 (c) Turbulent (i) Rc > 3000

 Column I Column II (a) Excess of pressure inside liquid drop (i) $$\frac {4T}{R}$$ (b) Excess of pressure inside liquid or soap bubble (ii) $$\frac {4T}{R}$$ (c) Excess of pressure inside an air bubble (iii) $$\frac {4T}{R}$$ (d) Upthrust (iv) V ρ g

 Column I Column II (a) Excess of pressure inside liquid drop (ii) $$\frac {4T}{R}$$ (b) Excess of pressure inside liquid or soap bubble (i) $$\frac {4T}{R}$$ (c) Excess of pressure inside an air bubble (iii) $$\frac {4T}{R}$$ (d) Upthrust (iv) V ρ g

 Column I Column II (a) Velocity head (i) $$\frac {P}{ ρ g}$$ (b) Pressure head (ii) h (c) gravitational head (iii) $$\frac {v^2}{ 2g}$$
 Column I Column II (a) Velocity head (iii) $$\frac {v^2}{ 2g}$$ (b) Pressure head (i) $$\frac {P}{ ρ g}$$ (c) gravitational head (ii) h