Mechanical properties of fluids Objective questions
Important multiple choice questions
1.. Viscosity is the property of liquids by virtue of which :
1) Liquid molecules attract each other
2) Liquid become conducting
3) Liquids oppose relative motion of its parts
4) None
2. The force acting tangential to the layers of the liquid is called :
1) Buoyant force
2) Viscous drag
3) Frictional force
4) Gravitational force
3. The property of viscosity in gas is due to :
1)Cohesive forces between the molecules
2) Collisions between the molecules
3) Not having a definite volume
4) Not having a definite size
4. Atomizer works on the
1) principle of continuity
2) Bernoullií's principle
3) Stoke's law
4) Archimedi's principle
5. When the wind blows at a high speed, the roof of a house is blown off because :
1) the pressure under the roof increases
2) Pressure above the roof increases
3) Pressure above the roof decreases
4) The wind pushes off the roof
6. When water flows from a narrow pipe into a broader pipe,
1) pressure decreases, rate of flow increases
2) pressure increases, velocity increases
3) rate of flow does not change but velocity increases
4) pressure increases, velocity decreases, rate of flow remains same
7. Among water and honey, viscosity is more for
1) Water 2) Honey
3) Same for both 4) None
8. For a body falling with terminal velocity, the net force on it is :
1) buoyant force
2) weight of the body
3) difference of viscous drag and
weight of the body
4) zero
9 As temperature increases, the viscosity of gases:
1) increases
2) decreases
3) does not change
4) may increase or decrease
10. v²/ 2g is called :
1) pressure head
2) gravitational head
3) both
4) none
11. Bernoulli's theorem is a consequence of
1) Law of conservation of energy
2) Law of conservation of mass
3) Law of conservation of linear momentum
4) None
12. Rain drops strike the earth with :
1) Same acceleration
2) Same constant velocity
3) Different constant velocities
4) Different accelerations
13. The correct statement of the following is
1) Layer of water with the ground is at rest
2) Deep water remains more quiet
3) Velocity of efflux does not depend upon density of the liquid
4) All of the above
14. A bird resting on the floor of an air tight box which is being carried by a boy. If the bird starts flying, he feels the box as :
1) Heavier
2) Lighter
3) Of same weight as before
4) Lighter in the beginning and heavier afterwards
15. As temperature increases; the viscosity of
1) Gases and liquids increase
2) Liquids and gases decrease
3) Gases increase but liquids decrease
4) Liquids increase but gases decrease
16. A body is floating in a liquid weight of the body
1) Equal to weight of the body
2) Equal to weight of the liquid displaced by the body
3) Less than the weight of the body
4) Zero
17. If the weight of the body and upthrust on the body in a liquid are equal, then the body
1) Sinks
2) Floats
3) Just completely immerses in the liquid
4) Completely lies out side the liquid
8. Unit of viscosity
1) Pa–s 2) Nm-2s
3) Poise 4) All of the above
19. Unit of velocity gradient
1) s 2) ms-1 3) s-1 4) m-1s1
20. The dimensional formula for rate of flow is
1)LT⁻¹
2 ) ML³T⁻¹
3) L³T⁻¹
4) L⁻³T¹
21. The dimensional formula of coefficient of viscosity is
1) ML⁻¹T⁻¹ 2) ML⁻²T⁻¹
3) M⁻¹L¹T⁻¹ 4) ML²T⁻³
22. Ratio of S.I. unit of Coefficient of viscosity to its C.G.S. unit is
1) 10 2) 0.1 3) 0.01 4) 100
23. As temperature of liquid increases, its viscosity
1)Increases
2) Decreases
3)Does not change
4)Gases do not have viscosity
24. The buoyant force is equal to
1) weight of the body
2) weight of the liquid displaced by the body
3) difference of the weight of the body and liquid displaced
4) none of the above
25. The ice is floating on water. When it is completely melted, the level of water
1) rises 2) decreases
3) remains same 4) none
26. Water stands at level A in the arrangement shown in figure . If a jet of air is gently blown into the horizontal tube in the direction shown in figure, then
1. Water will fall below A in the capillary tube
2. Water will rise above A in the capillary tube
3. There will be no effect on the level of water in the capillary tube
4. Air will emerge from end B in the form of bubbles.
27. Three tubes A, B, C are connected to a horizontal pipe in which liquid is flowing. The radii of the pipes at the joints of A, B and C are 2 cm, 1 cm and 2 cm respectively. The height of the liquid
1. in A is maximum
2. in A and C is equal
3. is same in all the three
4. in A and B is same 28. A body is floating in water such that 6 out of 10 parts of its volume is under water. Its density is
1) 0.6 gm/cc
2) 600 kg/m3
3) both
4) none
29. A liquid enters a tube of variable cross section with a velocity 3 ms-1 through the wider end and leaves from the narrower end whose radius is half of the wider one. The velocity with which it leaves the tube is
1) 1.2 ms-1
2) 12 ms-1
3) 10ms-1
4) 20 ms-1
30. A water hose 2 cm in diameter is used to fill a 20 litre bucket. If it takes 1 minute to fill the bucket, then the speed v at which the water leaves the hose is,
1) 150 cm/s
2) 70 cm/s
3) 100 cm/s
4) 106 cm/s
31. A metal ball of radius 'r' and density 'd' travels with a terminal velocity 'v' in a liquid of density d/4. The terminal velocity of another ball of radius '2r' and density '3d' in the same liquid is
1) 44v/3
2) 22v/3
3) 11v/3
4) 3v/44
32. A capillary tube of diameter 0.4mm is dipped in a beaker containing mercury. If density of mercury is 13.6 x 103 kg/m3, surface tension 0.49Nm–1, angle of contact 1350 the depression of the meniscus in the capillary tube will be
1) 0.13m
2) 0.013m
3) 0.026m
4) 0.0026m
34. A tank of height 5m is full of water. There is a hole of cross - sectional area 1 cm² in its bottom. The volume of water that will come out from this hole per second is
(g = 10 m/s²)
1) 10⁻³ m³/s 2) 10⁻⁴m³/s
3) 10 m³/s 4) 10⁻² m³/s
35. A piston of cross-sectional area 100 cm² is used in a hydraulic press to exert a force of 10⁷ dyne on water. The cross-sectional area of the other piston which supports a truck of mass 200 kg is,
1) 1.96 cm²
2) 0.196 m²
3) 0.98 m²
4) 98 m²
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