##### Q51. A weir is said to be narrow-crested weir, if the width of the crest of the weir is __________ half the height of water above the weir crest.

(a) More than
(b) Less than
(c) Equal to
(d) None of these

Ans: (b) Less than

##### Q52. In an immersed body, centre of pressure is

(a) Above the centre of gravity
(b) At the centre of gravity
(c) Below be centre of gravity
(d) Could be above or below e.g. depending on density of body and liquid

Ans: (c) Below be centre of gravity

##### Q53. A flow is called super-sonic if the

(a) Discharge is difficult to measure
(b) Velocity of flow is very high
(c) Mach number is between 1 and 6
(d) None of these

Ans: (c) Mach number is between 1 and 6

##### Q54. Which of the following relations is/are used in deriving the relation between the flow rate and the pressure difference between the straight section and the throat of a venturimeter that has no losses.                                    SSC JE 2019 S-II

(a) Ideal gas law
(b) Bernoulli and continuity equations
(c) Relation between friction factor and Reynolds number, and Bernoulli equation
(d) Bernoulli equation

Ans: (b) Bernoulli and continuity equations

##### Q55. Identify the incorrect statement from the following options:The total hydrostatic force on a flat thin sheet, immersed horizontally in water _____.                   SSC JE 2019 S-II

(a) can be considered to pass through its centre of gravity
(b) passes through a point that can be found by taking first moments of the area about x and y axes
(c) can be considered to pass through its centre of pressure
(d) is distributed along the edge

Ans: (d) is distributed along the edge

##### Q56. Identify the incorrect option regarding laminar flow in a pipe of diameter D.                     SSC JE 2019 S-II

(a) lower fluid velocity promotes laminar flow
(b) there is intermingling of fluid particles across the cross-section
(c) higher viscosity promotes laminar flow
(d) Re <= 2000

Ans: (b) there is intermingling of fluid particles across the cross-section

##### Q57. The torque required to overcome viscous resistance of a collar bearing is (where R1 andR2 = External and internal radius of collar)

(a) (μπ²N/60t) × (R₁ – R₂)
(b) (μπ²N/60t) × (R₁² – R₂²)
(c) (μπ²N/60t) × (R₁³ – R₂³)
(d) (μπ²N/60t) × (R₁4 – R₂4 )

Ans: (d) (μπ²N/60t) × (R₁4 – R₂4 )

##### Q58. The depth of centre of pressure (h) for a vertically immersed surface from the liquid surface is given by (where IG = Moment of inertia of the immersed surface about horizontal axis through its centre of gravity, A = Area of immersed surface, and x = Depth of centre of gravity of the immersed surface from the liquid surface)

(a) (IG/Ax ) – x
(b) (IG/x ) – Ax
(c) (Ax /IG) + x
(d) (IG/Ax ) + x

Ans: (d) (IG/Ax ) + x

##### Q59. If cohesion between molecules of a fluid is greater than adhesion between fluid and glass, then the free level of fluid in a dipped glass tube will be

(a) The same as the surface of liquid
(b) Higher than the surface of liquid
(c) Lower than the surface of liquid
(d) Unpredictable

Ans: (c) Lower than the surface of liquid

##### Q60. In a one-dimensional flow field in a pipe, the fluid velocity is given u = x + 2t where ‘t’ is the time.The flow in the pipe is:                                     SSC JE 2019 S-II

(a) Unsteady uniform flow
(b) Unsteady non-uniform flow
(c) Steady uniform flow
(d) Steady non-uniform flow

Ans: (b) Unsteady non-uniform flow

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Hydraulics and Fluid mechanics MCQ-Section-1

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Hydraulics and Fluid mechanics MCQ-Section-6