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Chemical engineering Fluid Mechanics Multiple choice Objective type questions with answers
1. A fluid is the one, which
(a) cannot remain at rest under the action of shear forces.
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(b) continuously expands till it fills fi lls any container. (c) is incompressible. incompressible. (d) permanently resists distortion.
2. In an incompressible fluid, the density is
(a) greatly affected by moderate changes in pressure. (b) greatly affected only by moderate changes in temperature. temperature. (c) not affected with moderate change in temperature & pressure. (d) sensible to changes changes in both temperature & pressure.
3. Potential flow is the of
(a) compressible fluids with shear. (b) compressible fluids with no shear. (c) incompressible fluids with shear. (d) incompressible fluids with no shear.
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4. Potential flow is characterized by the
(a) shear stress and velocity.
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(b) velocity gradient and pressure intensity.
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(c) shear stress rate of angular deformation in a fluid. (d) pressure gradient and rate of angular deformation.
5. Newton's law of viscosity relates the
(a) shear stress and velocity. (b) velocity gradient and pressure intensity. (c) shear stress and rate of angular deformation in a fluid. (d) pressure gradient and rate of angular deformation.
6. Dimension of absolute viscosity is
(a) ML-1 T-1
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(b) MLT (c) ML-1T (d) MLT
7. Poise is converted into stoke by
(a) multiplying with density (gm/c.c.). (b) dividing by density (gm/c.c.).
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(c) multiplying with specific gravity. (d) dividing by specific gravity.
8. Dimension of kinematic viscosity of a liquid
(a) MLT-1 (b) L2.T-1
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(c) L2 T (d) L2.T-2
9. With increase in the temperature, viscosity of a liquid
(a) increases (b) decreases
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(c) remains constant (d) may increase or decrease; depends on the liquid
10. For water, when the pressure increases, the viscosity
(a) also increases (b) decreases (c) remains constant (d) first decreases, and then increases
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11. The pressure intensity is the same in all directions at a point in a fluid
(a) only when the fluid is frictionless. (b) only when the fluid is at rest having zero velocity. (c) when there is no motion of one fluid layer relative to an adjacent layer. (d) regardless of the motion of one fluid layer relative to an adjacent layer.
12. Choose the set of pressure intensities that are equivalent.
(a) 4.33 psi, 10 ft. of water, 8.83 inches of Hg. (b) 4.33 psi, 10 ft. of water, 20.7 inches of Hg.
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(c) 10 psi, 19.7 ft. of water, 23.3 inches of Hg. (d) 10 psi, 19.7 ft. of water, 5.3 inches of Hg.
13. For a fluid rotating at constant angular velocity about vertical axis as a rigid body, the pressure intensity varies as the
(a) square of the radial distance.
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(b) radial distance linearly. (c) inverse of the radial distance. (d) elevation along vertical direction.
14. The centre of pressure is
(a) always below the centroid of the area. (b) always above the centroid of the area. (c) a point on the line of action of the resultant force.
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(d) at the centroid of the submerged area.
15. A rectangular surface 3' x 4', has the lower 3' edge horizontal and 6' below a free oil surface (sp. gr. 0.8). The surface inclination is 300 with the horizontal. The force on one side of the surface is
(a) 39.6y (b) 48y
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(c) 49.2y (d) 58y where,
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y = specific weight of water
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16. A stream tube is that, which has ..... cross-section entirely bounded by stream lines.
(a) a circular (b) any convenient
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(c) a small (d) a large
17. Mass velocity is independent of temperature & pressure, when the flow is
(a) unsteady through unchanged cross-section. (b) steady through changing cross-section. (c) steady and the cross-section is unchanged.
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(d) unsteady and the cross-section is changed.
18. In turbulent flow, the
(a) fluid particles move in an orderly manner. (b) momentum transfer is on molecular scale only. (c) shear stress is caused more effectively by cohesion than momentum transfer. (d) shear stresses are generally larger than in a similar laminar flow.
19. Turbulent flow generally occurs for cases involving
(a) highly viscous fluid (b) very narrow passages (c) very slow motion (d) none of these
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20. An ideal fluid is
(a) frictionless & incompressible.
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(b) one, which obeys Newton's law of viscosity. (c) highly viscous. (d) none of these.
21. Steady flow occurs, when the
(a) conditions change steadily with time. (b) conditions are the same at the adjacent points at any instant. (c) conditions do not change with time at any point.
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(d) rate of the velocity change is constant.
22. Which of the following by the flow of a fluid (real or ideal) ?
(i) Newton's law of viscosity. (ii) Newton's second law of motion. (iii) The continuity equation. (iv) Velocity of boundary layer must be zero relative to boundary. (v) fluid cannot penetrate a boundary. (a) I, II, III (b) II, III, V
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(c) I, II, V (d) II, II, V
23. Discharge from a 24 inch pipe of water at 10 f t./sec will be .... ft3 /sec.
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(a) 7.65 (b) 32.36 (c) 48.22 (d) 125.6
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24. The unit of velocity head is
(a) ft - 1b/sec (b) ft - 1b/ft3 (c) ft - 1bf/1b
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(d) ft - 1bf/sec
25. Bernoulli's equation describes the
(a) mechanical energy balance in potential flow.
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(b) kinetic energy balance in laminar flow. (c) mechanical energy balance in turbulent flow. (d) mechanical energy balance in boundary layer.
26. The kinetic energy correction factor for velocity distribution of laminar flow is
(a) 0.5 (b) 1.66
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(c) 1 (d) 2
27. In frictional fluid flow, the quantity, P/ + V 2 /2gc + gz/gc, is
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(a) constant along a streamline. (b) not constant along a streamline
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(c) increased in the direction of flow. (d) none of these.
28. The momentum correction factor for the velocity distribution of laminar flow is
(a) 1.3 (b) 1.66 (c) 2.5 (d) none of these
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29. The head loss due to sudden expansion is
(a) V 21 - V 22 / 2gc (b) (V 1 - V 2)2 / 2gc
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(c) V 1 - V 2 / 2gc (d) V 21 - V 22 / gc
30. The head loss due to sudden contraction is proportional to
(a) velocity (b) velocity head
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(c) turbulence (d) none of these
31. The value of critical Reynolds number for pipe flow is
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(a) 1300
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(b) 10,000 (c) 100,000 (d) none of these.
32. Reynolds number for flow of water at room temperature through 2 cm dia pipe at an average velocity of 5 cm/sec is around
(a) 2000 (b) 10 (c) 100 (d) 1000
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33. Shear stress in a fluid flowing in a round pipe
(a) varies parabolically across the cross-section. (b) remains constant over the cross-section. (c) is zero at the centre and varies linearly with the radius. (d) is zero at the wall and increases linearly to the centre.
34. Discharge in laminar flow through a pipe varies
(a) as the square of the radius.
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(b) inversely as the pressure drop. (c) inversely as the viscosity. (d) as the square of the diameter.
35. Boundary layer separation is caused by the
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(a) reduction of pressure below vapour pressure. (b) reduction of pressure gradient to zero. (c) adverse pressure gradient.
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(d) reduction of boundary layer thickness to zero.
36. The friction factor for turbulent flow in a hydraulically smooth pipe
(a) depends only on Reynolds number.
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(b) does not depend on Reynolds number. (c) depends on the roughness. (d) none of these.
37. For a given Reynolds number, in a hydraulically smooth pipe, further smoothening .......... the friction factor.
(a) brings about no further reduction of
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(b) increases (c) decreases (d) none of these
38. Hydraulic radius is the ratio of
(a) wetted perimeter to flow area. (b) flow area to wetted perimeter.
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(c) flow area to square of wetted perimeter. (d) square root of flow area to wetted perimeter.
39. Hydraulic radius of 6" x 12" cross-section, is...... inches.
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(a) 2
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(b) 0.5 (c) 1.5 (d) none of these
40. Reynolds number is the ratio of
(a) viscous forces to gravity forces. (b) inertial forces to viscous forces.
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(c) viscous forces to inertial forces. (d) inertial forces to gravity forces.
41. Mach number is the ratio of the speed of the
(a) fluid to that of the light. (b) light to that of the fluid. (c) fluid to that of the sound.
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(d) sound to that of the fluid.
42. Power loss in an orificemeter is ............ that in a venturimeter.
(a) less than (b) same as (c) more than
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(d) data insufficient, cannot be predicted
43. The velocity profile for turbulent flow through a closed conduit is
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(a) logarithmic
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(b) parabolic (c) hyperbolic (d) linear
44. For laminar flow through a closed conduit
(a) V max = 2 V av
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(b) V max = V av (c) V max = 1.5 V av (d) V max = 0.5 V av
45. f = 16/N Re, is valid for
(a) turbulent flow (b) laminar flow through an open channel (c) steady flow (d) none of these
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46. Isotropic turbulence occurs
(a) where there is no velocity gradient.
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(b) at higher temperatures. (c) only in Newtonion fluids. (d) none of these.
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47. Consider two pipes of same length and diameter through which water is passed at the same velocity. The friction factor for rough pipe is f 1 and that for smooth pipe is f 2. Pick out the correct statement.
(a) f 1 = f 2 (b) f 1 < f 2 (c) f 1 > f 2
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(d) data not sufficient to relate f 1 & f 2
48. Bernoulli's equation for steady, frictionless, continuous flow states that the ...... at all sections is same.
(a) total pressure (b) total energy
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(c) velocity head (d) none of these
49. Drag is defined as the force exerted by the
(a) fluid on the solid in a direction opposite to flow. (b) fluid on the solid in the direction of flow.
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(c) solid on the fluid. (d) none of these.
50. Drag co-efficient for flow past immersed body is the ratio of ........ to the product of velocity head and density.
(a) shear stress (b) shear force (c) average drag per unit projected area
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(d) none of these
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