Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q5. If pressure at half the depth of a lake is equal to
2/3rd the pressure at the bottom of the lake, then the
Q1. An airplane of a total wing area of 120 m is in depth of the lake is:
a level flight at some height. If the pressure difference 1. 10m
between the upper and lower surface is 2.5 kPa, then the 2. 20m
3. 60m
mass of the airplane is: [Take g = 10 ms ]
4. 30m
1. 2 x 10 kg
Pressure - Level I
2
−2
3
2. 3 x 10
3. 5 x 10
4. 7 x 10
4
4
7
kg
kg
kg
Q2. From the adjacent figure, the correct observation is:
1. Pressure at the bottom of the tank (a) is greater than at
the bottom of the tank (b).
2. Pressure at the bottom of the tank (a) is lesser than at
the bottom of (b).
3. Pressure depends upon the shape of the container.
4. Pressure at the bottom of (a) and (b) are the same.
Q6. The area of cross-section of the wider tube shown in
the figure is 800 cm . If a mass of 12 kg is placed on
the massless piston, then the difference in heights h of
the levels of water in the two tubes will be:
2
1. 10 cm
2. 6 cm
3. 15 cm
4. 2 cm
Q7. The value of g at a place decreases by 2%. Then, the
barometric height of mercury:
Q3. A liquid is poured into three vessels of the 1. increases by 2%.
same base area and equal heights as shown in the figure, 2. decreases by 2%.
then:
3. remains unchanged.
4. sometimes increases and sometimes decreases.
Q8. The height of a mercury barometer is 75 cm at sea
level and 50 cm at the top of a hill. The ratio of density
of mercury to that of air is 10 . The height of the hill is:
1. 250 m
2. 2.5 km
3. 1.25 km
4. 750 m
4
1. Maximum force on the base will be for vessel C
2. Maximum force on the base will be for vessel B
3. Maximum force on the base will be for vessel A
4. Force on the base will be equal for all the vessels
Q4. A diver is 10 m below the surface of water. The
approximate pressure experienced by the diver is1. 105 Pa
2. 2 × 105 Pa
3. 3 × 105 Pa
4. 4 ×105 Pa
Page: 1
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q9. A siphon in use is demonstrated in the following
figure. The density of the liquid flowing in the siphon is
1.5 gm/cc. The pressure difference between the point P
and S will be:
Q11. An inverted bell lying at the bottom of a lake 47.6
m deep has 50 cm3 of air trapped in it. The bell is
brought to the surface of the lake. The volume of the
trapped air will be: (atmospheric pressure = 70 cm of Hg
and density of Hg = 13.6 g/cm3)
1. 350 cm3
2. 300 cm3
3. 250 cm3
4. 22 cm3
Q12. A barometer kept in a stationary elevator reads 76
cm. If the elevator starts accelerating up, the reading will
be:
1. zero.
2. equal to 76 cm.
3. more than 76 cm.
4. less than 76 cm.
1. 10 N/m
2. 2 × 10 N/m
3. Zero
4. Infinity
5
5
Q13. There are four cylindrical vessels identical
in dimensions. If these are filled with equal masses of
Q10. A vertical U-tube of uniform inner cross section, four different liquids P, Q, R, and S such that their
contains mercury in both its arms. A glycerin (density = densities are ρ > ρ > ρ > ρ , then pressure at
1.3 g/cm ) column of length 10 cm is introduced into the base of vessel will be:
one of its arms. Oil of density 0.8 gm/cm is poured into 1. P = P = P = P
the other arm until the upper surfaces of the oil and 2. P > P > P > P
glycerin are at the same horizontal level. Find the length 3. P < P < P < P
4. Data is insufficient to predict the relation
of the oil column. [Density of mercury = 13.6 g/cm ]
p
Q
R
S
3
3
p
Q
R
S
p
Q
R
S
p
Q
R
S
3
Pressure - Level II
Q14. A mercury-filled U–tube arrangement is connected
to a bulb containing a gas. Atmospheric pressure is
1.012 × 105 Pa and H = 0.05 m. Gauge pressure at R is?
1. 10.4 cm
2. 8.2 cm
3. 7.2 cm
4. 9.6 cm
1. Nil
2. 6.56 × 103 Pa
3. 1.08 × 105 Pa
4. pressure at R, Q, and inside the bulb are the same.
Page: 2
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q15. A U tube is partially filled with water. Oil which
is immiscible in water is poured into one side until the
water rises by 25 cm on the other side. If the oil level
is 12.5 cm higher than the water level, then the relative
density of the oil is:
1. 0.3
2. 0.5
3. 0.8
4. 1.2
Q19. A tank is filled with water upto a height h and the
pressure at the bottom of the tank is 3P where P is the
atmospheric pressure. The height of a point from the
bottom of the tank where pressure is
is11P
5
1.
2h
2.
3h
5
5
4h
3.
4. None of these
5
Q16. A triangular lamina of area A and height h is
Types of Flows - Level I
immersed in a liquid of density ρ in a vertical plane with
its base on the surface of the liquid. The thrust on the
Q20. Which of the following diagrams does not
lamina is:
represent a streamline flow?
1. Aρgh
1
2
2.
1
3.
1
4.
2
3
6
3
Aρgh
Aρgh
Aρgh
Q17. The heart of a man pumps 5L of blood through the
arteries per minute at a pressure of 150 mm of mercury.
If the density of mercury is 13.6 × 10 kg/m3 and g =10
m/s2, then the power of heart in watt is:
1. 1.70
2. 2.35
3. 3.0
4. 1.50
3
Q18. A liquid is filled in a container as shown in
the figure. The force exerted by the liquid on the base of
the container must be:
Q21. When a large bubble rises from the bottom of
a lake to the surface, its radius doubles. The atmospheric
pressure is equal to that of a column of water of height
H. The depth of the lake is:
1. H
2. 2H
3. 7H
4. 8H
Properties of Fluids - Level I
Q22. Three liquids of densities d, 2d and 3d are mixed in
equal proportions of weights. The relative density of the
mixture is:
1.
11d
7
1. Equal to the weight of the liquid
2. More than the weight of the liquid
3. Less than the weight of the liquid
4. More or less than the weight of the liquid
2.
18d
3.
13d
4.
23d
11
9
18
Archimedes' Principle - Level I
Q23. An iceberg of density 900 kg/m is floating in
water of density 1000 Kg/m . The percentage of volume
of ice-cube outside the water is:
1. 20%
2. 35%
3. 10%
4. 25%
3
3
Page: 3
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q24. If two iron balls when fully immersed in water
experience thrust force in the ratio of 1:2, then the ratio
of the masses of the balls will be:
1. 1: 1
2. 1: 2
3. 2: 1
4. 1: 4
Q25. When a man sits on a boat of length 2 m
and breadth 1 m floating on a lake, the boat sinks by 2
cm. The mass of the man is:
1. 25 kg
2. 40 kg
3. 60 kg
4. 80 kg
Q30. Two non-mixing liquids of densities ρ and nρ
(n>1) are put in a container. The height of each liquid is
h. A solid cylinder floats with its axis vertical and
length pL (p < 1) in the denser liquid. The density of
the cylinder is d. The density d is equal to:
1. {2+(n+1)p}ρ
2. {2+(n-1)p}ρ
3. {1+(n-1)p}ρ
4. {1+(n+1)p}ρ
Q31. If two pieces of metal when immersed in a liquid
have equal upthrust on them, then:
1. Both pieces must have equal weights
2. Both pieces must have equal densities
3. Both pieces must have equal volumes
4. Both are floating in the same depth
Q26. A body of density 0.7 gm/cm floats on a lake of
water. The fraction of the body which is outside water is1. 30%
2. 70%
3. 25%
4. 50%
3
Q32. A boat carrying steel balls is floating on the
surface of water in a tank. If the balls are thrown into the
tank one by one, how will it affect the level of water ?
1. It will remain unchanged
2. It will rise
3. It will fall
Q27. A block weighs 5 N in air and 4.5 N in a liquid 4. First it will first rise and then fall
of specific gravity 0.5. Its weight in water will be:
1. 3.5 N
Q33. A wooden block with a coin placed on its top,
2. 4.0 N
floats in water as shown in fig. The distance l and h are
3. 2.5 N
shown there. After some time the coin falls into the
4. 3.0 N
water. Then:
Q28. The reading of a spring balance when a block
is suspended from it in the air is 60 N. This reading is
changed to 40 N when the block is submerged in water.
The specific gravity of the block, therefore, must be:
1. 3
2. 2
3. 6
4. 3/2
Q29. A beaker full of water is placed on a
spring balance. If we put our finger in water without
touching the beaker, how will the reading of the balance
change? [Take ρ
> ρ
]
1. Increase
2. Decrease
3. Remain the same
4. Will be halved
finger
water
1. l decreases and h increases
2. l increases and h decreases
3. Both l and h increase
4. Both l and h decrease
Page: 4
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q34. A candle of diameter d is floating on a liquid in a Q38. A block of ice floats on a liquid of density 1.2
cylindrical container of diameter D (D>>d) as shown in g/cm in a beaker. The level of liquid when ice
figure. If it is burning at the rate of 2cm/hour then the completely meltstop of the candle will:
1. Remains same
2. Rises
3. Lowers
4. (1), (2) or (3)
3
Q39. A hemispherical bowl just floats without sinking in
a liquid of density 1. 2 × 10 kg /m . If the outer
diameter and the density of the material of the bowl are
1 m and 2 × 10 kg /m respectively, then the inner
diameter of the bowl will be:
1. 0.94 m
2. 0.97 m
3. 0.98 m
4. 0.99 m
3
4
1. Remain at the same height
2. Fall at the rate of 1 cm/hour
3. Fall at the rate of 2 cm/hour
4. Go up at the rate of 1cm/hour
3
3
Q40. A solid sphere of density η ( > 1) times lighter than
water is suspended in a water tank by a string tied to its
Q35. A body is just floating on the surface of a liquid. base as shown in fig. If the mass of the sphere is m, then
The density of the body is the same as that of the liquid. the tension in the string is given by:
The body is slightly pushed down. What will happen to
the body ?
1. It will slowly come back to its earlier position
2. It will remain submerged, where it was left
3. It will sink
4. It will come out violently
Q36. Two bodies are in equilibrium when suspended in
water from the arms of a balance. The mass of one body
is 36 g and its density is 9 g / cm3. If the mass of the
1. (
)mg
other is 48 g, its density in g / cm3 will be:
2. ηmg
1.
3.
2.
4. (η − 1) mg
3. 3
4. 5
Q41. A solid is suspended from an independent support
in a liquid placed on a weighing machine, due to which
Archimedes' Principle - Level II
the weight of the liquid:
1. Increases
Q37. A concrete sphere of radius R has a cavity of 2. Decreases
radius r which is packed with sawdust. The specific 3. Remain unchanged
gravities of concrete and sawdust are respectively 2.4 4. May increase or decrease
and 0.3. For this sphere to float with its entire volume
submerged underwater, the ratio of mass of concrete to
mass of sawdust will be:
1. 8
2. 4
3. 3
4. Zero
η−1
η
4
3
3
mg
η
2
Page: 5
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q42. A metallic sphere with an internal cavity weighs
40 g wt in air and 20 g wt in water. If the density of the
material with the cavity is 8 g/ cm3 , then the volume
of the cavity is:
1. 0 cm
2. 5 cm
3. 20 cm
4. 15 cm
3
3
3
3
Equation of Continuity - Level I
Q43. From the given diagram, the velocity v is:
3
1. 4 m/s
2. 3 m/s
3. 1 m/s
4. 2 m/s
Q45. In a horizontal pipe of non-uniform cross-section,
water flows with a velocity of 1 m s at a point where
the diameter of the pipe is 20 cm. The velocity of water
(m s ) at a point where the diameter of the pipe is 5 cm
is1. 8
2. 16
3. 24
4. 32
−1
−1
Q46. An incompressible fluid flows steadily through a
cylindrical pipe which has a radius 2r at point A and a
radius r at B further along the flow direction. If the
velocity at point A is v, its velocity at point B is:
1. 2v
2. v
3. v/2
4. 4v
Q47. The cylindrical tube of a spray pump has radius R,
one end of which has n fine holes, each of radius r. If the
speed of the liquid in the tube is v, then the speed of
ejection of the liquid through the holes will be:
1. vR2/n2r2
2. vR2/nr2
3. vR2/n3r2
4. v2R/nr
Q44. If an incompressible liquid is flowing through Q48. The diameter of a syringe is 4 mm and the
a horizontal pipe having branches of area A, 0.4 A, and diameter of its nozzle (opening) is 1 mm. The syringe is
0.5 A as shown in the figure, then the value of v is:
placed on the table horizontally at a height of 1.25 m. If
the piston is moved at a speed of 0.5 m/s, then
considering the liquid in the syringe to be ideal, the
horizontal range of liquid is(g = 10 m/s )
1. 4 m
2. 8 m
3. 0.4 m
4. 0.2 m
2
Equation of Continuity - Level II
1. 3.2 m/s
2. 6.4 m/s
3. 1.6 m/s
4. 0.8 m/s
Q49. Equation of continuity is based on :
1. Conservation of mass
2. Conservation of energy
3. Conservation of angular momentum
4. None of these
Page: 6
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q50. Water flows through a frictionless duct with a
Bernoulli's Theorem - Level I
cross-section varying as shown in the figure. Pressure p
at points along the axis is represented by:
Q51. A large open tank with a square hole of side
0.1 cm in the wall at a depth of 0.2 m from the top is
completely filled with a liquid. The rate of flow of liquid
(in cm /s) through the hole will be1. 1
2. 2
3. 3
4. 4
3
Q52. A tank is filled with water up to a height H. Water
is allowed to come out of a hole P in one of the walls at
a depth D below the surface of water. Express the
horizontal distance x in terms of H and D
1.
2.
1. x = √D(H − D)
2. x = √
D(H−D)
2
3.
4. x = 4√D(H − D)
x = 2√D(H − D)
3.
4.
Q53. The pressure of water in a water pipe when tap is
opened and closed are respectively 3 × 105 Nm–2 and
3.5 × 105 Nm–2. With open tap, the velocity of water
flowing is:
1. 10 ms–1
2. 5 ms–1
3. 20 ms–1
4. 15 ms–1
Page: 7
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q54. The following fig. shows the flow of liquid
through a horizontal pipe. Three tubes A, B and C are
connected to the pipe. The radii of the tubes A, B and C
at the junction are respectively 2 cm, 1 cm and 2 cm. It
can be said that the:
Q58. In a horizontal pipe line the pressure falls by
16 Nm
between two points separated by a distance of
2 km. Density of oil is 800 kg m . Change in kinetic
energy per kg of the oil flowing in the tube is:
1. 2 × 10 J/ kg
2. 2 × 10 J/ kg
3. 2 × 10 J/ kg
4. 2 × 10 J/ kg
−2
−3
3
2
−2
−3
Q59. A small hole of an area of cross-section 2 mm is
present near the bottom of a fully filled open tank of
height 2 m. Taking g= 10 m/s , the rate of flow of
water through the open hole would be nearly:
1. 6. 4 × 10 m /s
2. 12. 6 × 10 m /s
3. 8. 9 × 10 m /s
4. 2. 23 × 10 m /s
2
2
−6
3
−6
1. Height of the liquid in the tube A is maximum
2. Height of the liquid in the tubes A and B is the same
3. Height of the liquid in all the three tubes is the same
4. Height of the liquid in the tubes A and C is the same
−6
−6
3
3
3
Q60. The speed of flow past the lower surface of a wing
of an aeroplane is 50 m/s. What speed of flow over the
Q55. A horizontal pipe line carries water in a streamline upper surface will give a dynamic lift of 1000 Pa?
flow. At a point along the pipe where cross-sectional (Density of air = 1.3 kg/m3):
area is 10 cm2, the velocity of water is 1 m/s and
pressure is 2000 Pa. The pressure of water at another
point where cross-sectional area is 5 cm2, is: (Density of
water=1000 kg/m3)
1. 250 Pa
2. 500 Pa
3. 1000 Pa
4. 2000 Pa
Q56. There is an orifice at some depth in the water tank.
Absolute pressure at the level of the orifice in the water
tank is 4 atmospheric pressure. The density of water is
10
kg /m and 1 atm pressure = 10 N/m . The speed
of water coming out of the orifice is:
1. 10 m/s
2. 20 m/s
3. 10√6 m/s
4. 10√2 m/s
3
5
3
2
1. 25.55 m/s
2. 63.55 m/s
3. 13.25 m/s
4. 6.355 m/s
Q57. The velocity of kerosene oil in a horizontal pipe is
5 m/s. If g = 10m/s , then the velocity head of oil will
be:
1. 1.25 m
2. 12.5 m
3. 0.125 m
4. 125 m
2
Page: 8
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q61. Water flows through a frictionless tube with
a varying cross-section as shown in the figure. Variation
of pressure P at point x along the axis is roughly given
by:
Q63. An engine pumps water continuously through a
hose. Water leaves the hose with a velocity v and m is
the mass per unit length of the water jet. What is the rate
at which kinetic energy is imparted to water?
1. mv
1
3
2
2. mv
3. mv
3
1
2
2
4.
1.
2.
1
2
2
m v
2
Q64. Find the rate of flow of glycerine of density 1.25 ×
103 kg/m3 through the conical section of a pipe, if the
radii of its ends are 0.1m and 0.04 m and the pressure
drop across its length is 10N/m2.
1. 3.14 × 10–4 m3/s
2. 6.28 × 10–4 m3/s
3. 12.56 × 10–4 m3/s
4. 1.57 × 10–4 m3/s
Q65. A wind with speed 40 m/s blows parallel to the
roof of a house. The area of the roof is 250 m2.
Assuming that the pressure inside the house is
atmospheric pressure, the force exerted by the wind on
the roof and the direction of the force will be
(Pair=1.2kg/m3)
1. 4.8x105N, downwards
2. 4.8x105N, upwards
3. 2.4x105N, upwards
4. 2/4x105N, downwards
3.
Q66. The pans of a physical balance are in equilibrium.
If Air is blown under the right hand pan then the right
hand pan will:
1. Move up
2. Move down
3. Move erratically
4. Remain at the same level
4.
Q67. There is a hole in the bottom of a tank having
water. If the total pressure at the bottom is 3 atm (
Q62. A tank has an orifice near its bottom. The volume
1 atm = 10 N/m ), then the velocity of water flowing
of the liquid flowing per second out of the orifice does
from the hole is:
not depend upon:
1. √400 m/s
1. the area of the orifice.
2. √600 m/s
2. the height of the liquid level above the orifice.
3. √60 m/s
3. the density of the liquid.
4. None of these
4. acceleration due to gravity.
5
2
Page: 9
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q70. A sniper fires a rifle bullet into a gasoline tank
making a hole 53.0 m below the surface of gasoline. The
Q68. An L-shaped tube with a small orifice is held in a tank was sealed at 3.10 atm. The stored gasoline has a
water stream as shown in fig. The upper end of the tube density of 660 kgm . The velocity with which gasoline
is 10.6 cm above the surface of water. What will be the begins to shoot out of the hole will be:
height of the jet of water coming from the orifice? 1. 27.8 ms
2. 41.0 ms
Velocity of water stream is 2.45 m/s.
3. 9.6 ms
4. 19.7 ms
Bernoulli's Theorem - Level II
−3
−1
−1
−1
−1
Q71. From the given diagram, the speed with which
water leaves the tube B of small diameter is-
1. Zero
2. 20.0 cm
3. 10.6 cm
4. 40.0 cm
Q69. A water tank is kept at a height H above
the ground and the tank contains depth H of water as 1. √2 gh
shown. Find the maximum possible range of water 2. √2 gh
current, if there exists a small hole on the sidewall of the 3. √2g(h
tank.
4. √2g(h
1
2
1
+ h2 )
2
− h1 )
Q72. Fluid flows through a pipe in a horizontal plane.
The fluid has a relative density of 0.9 and its velocity at
P (where cross-section area is A) is 4 m/s. What is its
pressure at Q (where cross-section area is )? The
pressure at P is 2.8 x 10 Pa.
A
4
5
1. 2H
2.
3H
2
3.
4. H
5H
2
1. 2.36 x 10 Pa
2. 3.88 x 10 Pa
3. 2.08 x 10 Pa
4. 1.72 x 10 Pa
5
5
5
5
Page: 10
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q73. Water flows through a horizontal tube as shown in
figure. If the difference in heights of water column in
vertical tubes is 80 cm and the area of cross-section at A
and B are 5 cm2 and 3 cm2 respectively, then the rate of
flow of water at A( in cc/sec) is:[T ake g = 10 m/s ]
2
1. 15 × 10
2. 15 × 10
3. 150
4. None of these
2
3
Viscosity - Level I
Q75. A spherical ball of radius 'r' is falling in a viscous
fluid of viscosity 'η' with a velocity 'v'. The retarding
viscous force acting on the spherical ball is:
1. inversely proportional to 'r' but directly proportional
to velocity 'v'.
2. directly proportional to both radius 'r' and velocity 'v'.
3. inversely proportional to both radius 'r' and velocity
'v'.
4. directly proportional to 'r' but inversely proportional
to 'v'.
Q76. The relative velocity of two adjacent layers of
a liquid is 6 cm/s and the perpendicular distance between
layers is 0.1 mm. The velocity gradient for liquid (in per
second) is:
1. 6
2. 0.6
3. 0.06
4. 600
Q77. With an increase in temperature, the viscosity of:
Q74. An ideal fluid is flowing in a steady-state from a. gases decreases.
section A to B through a pipe in a vertical plane as b. liquids increases.
shown. Select the incorrect statement.
c. gases increases.
d. liquids decreases.
1. (b, c)
2. (a, d)
3. (c, d)
4. (a, b)
Q78. The velocity of a small ball of mass m and density
ρ when dropped in a container filled with glycerine of
density σ becomes constant after sometime. The viscous
force acting on the ball in the final stage is:1. mg( )
1. Total energy per unit volume is the same at
both sections A and B
2. mg(1 +
2. The incoming flow rate at A is equal to the outgoing
3. mg(1 −
flow rate at B
3. Loss in kinetic energy of the fluid is equal to gain in 4. mg
potential energy from section A to section B
4. The flow of fluid from A to B is laminar flow
σ
ρ
σ
ρ
σ
ρ
)
)
Page: 11
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q79. A metal block of area 0. 10 m is connected to a
0.010 kg mass via a string that passes over an ideal
pulley (considered massless and frictionless), as in the
figure below. A liquid film with a thickness of 0.30 mm
is placed between the block and the table. When released
the block moves to the right with a constant speed of
0.085 m/s. The coefficient of viscosity of the liquid is:
Stokes' Law - Level I
2
Q82. Two small spherical metal balls, having equal
masses, are made from materials of densities ρ and ρ
such that ρ = 8ρ and having radii of 1 mm and 2 mm,
respectively. They are made to fall vertically (from rest)
in a viscous medium whose coefficient of viscosity
equals η and whose density is 0.1ρ . The ratio of their
terminal velocities would be:
1.
1
1
2
2
2
79
72
2.
19
3.
39
4.
79
36
72
36
Q83. A small spherical solid ball is dropped in a viscous
liquid. Its journey in the liquid is best described in the
figure by :
1.
2.
3.
4.
4. 45 × 10
4. 45 × 10
3. 45 × 10
3. 45 × 10
−2
−3
−2
−3
Pa − s
Pa − s
Pa − s
Pa − s
Viscosity - Level II
Q80. With an increase in temperature, the viscosity of
liquid and gas, respectively will:
1. increase and increase
2. increase and decrease
3. decrease and increase
4. decrease and decrease
1. Curve A
2. Curve B
3. Curve C
4. Curve D
Q84. A small tiny water droplet is falling towards earth
at a uniform speed of 1 cm/s. When 27 such identical
Q81. A square plate of 0.1 m side moves parallel to a droplets combine together to form a bigger drop, then
second plate with a velocity of 0.1 m/s, both plates being with what uniform velocity will this bigger drop fall?
immersed in water. If the viscous force is 0.002 N and 1. 27 cm/s
the coefficient of viscosity is 0.01 poise, then the 2. 9 cm/s
3. 3 cm/s
distance between the plates in m is:
4. 81 cm/s
1. 0.1
2. 0.05
Q85. If a small drop of water falls from rest through a
3. 0.005
large height h in air, then the final velocity is:
4. 0.0005
1. ∝ √h
2. ∝ h
3. ∝ (1/h)
4. Almost independent of h
Page: 12
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q86. An iron sphere is dropped into a viscous
Surface Tension - Level I
liquid. Which of the following represents its acceleration
(a) versus time (t) graph?
Q88. A spherical drop of water has a radius of 1 mm. If
the surface tension of water is 70 × 10
N/m, the
difference in pressures inside and outside the spherical
drop is:
1. 35 N/m
2. 70 N/m
3. 140 N/m
4. Zero
1.
Q89. The property of surface tension of the liquid is due
to:
1. the gravitational force of attraction between
the molecules.
2. the cohesive forces between the molecules.
3. the adhesive force between the molecules.
4. the formation of ionic bonds between the molecules.
−3
2
2
2
Q90. In order to float a ring of area 0.04 m in a liquid
of surface tension 75 N/m, the required surface energy
will be:
1. 3 J
2. 6.5 J
3. 1.5 J
4. 4 J
2
2.
Q91. Small droplets of liquid are usually more spherical
in shape than the larger drops of the same liquid
because:
1. the force of surface tension is equal and opposite to
the force of gravity.
2. the force of surface tension predominates the force of
gravity.
3. the force of gravity predominates the force of surface
tension.
4. the force of gravity and the force of surface tension
act in the same direction and are equal.
3.
4.
Q92. If the excess pressure inside a soap bubble is
balanced by an oil column of height of 2 mm, then the
surface tension of the soap solution will be:
Q87. A small sphere of radius 'r' falls from rest in a (radius of the soap bubble,r = 1 cm and density of oil, d
viscous liquid. As a result, heat is produced due to the = 0.8 gm/cc)
viscous force. The rate of production of heat when the 1. 3.9 N/m
sphere attains its terminal velocity is proportional to:
2. 3. 9 × 10 N/m
1. r
3. 3. 9 × 10 N/m
2. r
4. 3.9 dyne/m
3. r
Stokes' Law - Level II
−2
3
−3
2
5
4. r
4
Page: 13
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q93. The energy needed to break a drop of radius R into Q97. A certain number of spherical drops of a liquid of
n drops of radii r is given by:
radius r coalesce to form a single drop of radius R and
volume V. If T is the surface tension of the liquid, then:
1. 4πT(nr − R )
2
2.
4
3
3
2
2
π(r n − R )
3. 4πT(R − nr )
4. 4πT(r n + R )
2
2
2
1. Energy = 4V T (
1
2. Energy = 3V T (
1
3. Energy = 3V T (
1
r
r
−
+
2
Q94. A wooden stick 2 m long is floating on the surface
of the water. The surface tension of water is 0.07 N/m.
By putting soap solution on one side of the stick, the
surface tension is reduced to 0.06 N/m. The net force on
the stick due to surface tension will be:
1. 0.07 N
2. 0.06 N
3. 0.01 N
4. 0.02 N
r
−
1
R
1
R
1
R
) is released
) is released
) is released
4. Energy is neither released nor absorbed
Q98. An air bubble of radius r in water is at a certain
depth below the water surface. If P is the pressure inside
the bubble, then the depth below the water surface is:
(P = Atmospheric pressure, ρ = Density of water, T =
surface tension of water]
0
1.
P − P0
2.
P + P0
−
ρg
+
ρg
4T
rρg
2T
rρg
Q95. The surface tension of a liquid is 5 N m . If a 3.
−
film is held on a ring of area 0.02 m , then its total
4.
+
surface energy is:
1. 3 x 10 J
Q99. A rectangular film of liquid is extended from (4 cm
2. 2 x 10 J
× 2 cm) to (5 cm × 4 cm). If the work done is
3. 3 x 10 J
3 × 10
J, the value of the surface tension of the liquid
4. 10 J
is:
Q96. Two soap bubbles are connected by a tube as 1. 0.250 Nm-1
shown in the figure. Which of the following statement is 2. 0.125 Nm-1
true?
3. 0.2 Nm-1
4. 8.0 Nm-1
−1
2
P − P0
2T
ρg
rρg
P − P0
2T
ρg
2rρg
−2
−1
−3
−1
−4
Surface Tension - Level II
Q100. The radius of a soap bubble is increased from R
to 2 R. Work done in this process (T = surface tension)
is:
1. 24 πR T
2. 48 πR T
3. 12 πR T
4. 36 πR T
2
2
2
1. The volume of A will increase.
2. The volume of A will remain constant.
3. The volume of B will increase.
4. The volume of B will decrease.
2
Page: 14
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q101. A soap bubble is blown with the help of a
mechanical pump at the mouth of a tube. The pump
produces a certain increase per minute in the volume of
the bubble, irrespective of its internal pressure. The
graph between the pressure inside the soap bubble and
time t will be-
1.
Q103. A soap bubble, having a radius of 1 mm, is blown
from a detergent solution having a surface tension of
2. 5 × 10
N /m. The pressure inside the bubble equals
at a point Z below the free surface of the water in a
container. Taking g= 10 m/s , density of water =
10 kg/m , the value of Z is:
1. 0.5 cm
2. 100 cm
3. 10 cm
4. 1 cm
−2
0
2
3
3
0
Q104. There is a horizontal film of soap solution. On it,
a thread is placed in the form of a loop. The film is
pierced inside the loop and the thread becomes a circular
loop of radius R. If the surface tension of the loop is T,
then what will be the tension in the thread?
1. πR /T
2. πR T
3. 2πRT
4. 2 RT
2
2
2.
3.
4.
Q102. A liquid drop at temperature T, isolated from its
surroundings, breaks into a number of droplets. The
temperature of the droplets will be–
1. equal to T
2. greater than T
3. less than T
4. either (1), (2) or (3) depending on the surface tension
of the liquid.
Page: 15
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q107. Water rises to height h in a capillary tube. If the
length of the capillary tube above the surface of water is
Q105. Which of the following graph represents the made less than h, then:
variation of capillary rise of liquid with radius of the 1. water does not rise at all.
2. water rises up to the top of the capillary tube, then
capillary tube?
starts overflowing like a fountain.
3. water rises up to the top of the capillary tube and stays
there without overflowing.
4. water rises up to a point a little below the top and
stays there.
Capillary Rise - Level I
Q108. 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
1.
Q109. If a capillary tube is partially dipped vertically
into liquid and the levels of the liquid inside and outside
are same, then the angle of contact is
1. 90°
2. 30°
3. 45°
4. 0°
2.
Q110. Water rises to a height h in a capillary at the
surface of earth. On the surface of the moon, the height
of water column in the same capillary will be1. 6h
2. h
3. h
4. Zero
1
3.
6
Q111. A liquid filled in a container has plane
meniscus. If θ is the angle of contact, then:
1. θ = 0°
2. θ = 90°
3. θ < 90°
4. θ = 180°
4.
Q106. If the surface tension of water is 0.06 Nm , then
the capillary rise in a tube of diameter 1 mm is:( θ=0° )
1. 1.22 cm
2. 2.44 cm
3. 3.12 cm
4. 3.86 cm
−1
Q112. If the capillary experiment is performed in a
vacuum, then for a liquid the capillary will:
1. rise
2. remain the same
3. fall
4. Rise to the top
Page: 16
Recommended MCQs - 120 Questions - Mechanical
Contact Number: 9667591930 / 8527521718
Properties of Fluids
Q113. Three liquids of densities ρ , ρ and ρ (with
ρ > ρ > ρ ), having the same value of surface tension
T, rise to the same height in three identical capillaries.
The angles of contact θ , θ and θ obey
1. > θ > θ > θ ≥ 0
2. 0 ≤ θ < θ < θ <
3. < θ < θ < θ < π
4. π > θ > θ > θ >
1
1
2
2
3
3
1
2
3
π
2
1
2
3
π
1
2
3
2
π
2
1
2
3
1
2
3
π
2
Capillary Rise - Level II
Q114. A capillary tube of radius r is immersed in water
and water rises in it to a height h. The mass of the water
in the capillary is 5g. Another capillary tube of radius 2r
is immersed in water. The mass of water that will rise in
this tube is :
1. 5.0 g
2. 10.0 g
3. 20.0 g
4. 2.5 g
Q115. Water rises in a capillary tube to a certain height
such that the upward force due to surface tension is
balanced by 75 × 10 N force due to the weight of the
liquid. If the surface tension of water is 6 × 10 Nm
, the inner circumference of the capillary must be
1. 1. 25 × 10 m
2. 0. 50 × 10 m
3. 6. 5 × 10 m
4. 12. 5 × 10 m
−4
−2
−1
−2
−2
−2
−2
Q116. In a capillary tube experiment, a vertical 30 cm
long capillary tube is dipped in water. The water rises up
to a height of 10cm due to capillary action. If this
experiment is conducted in a freely falling elevator, the
length of the water column becomes1. 10 cm
2. 20 cm
3. 30 cm
4. Zero
Q117. In a capillary tube, pressure below the curved
surface of the water will be:
1. equal to atmospheric pressure.
2. equal to upper side pressure.
3. more than upper side pressure.
4. lesser than upper side pressure.
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