Hydraulics and Fluid Mechanics MCQ – Set 17

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Q1. The increase of temperature results in

(A) Increase in viscosity of gas
(B) Increase in viscosity of liquid
(C) Decrease in viscosity of gas
(D) Decrease in viscosity of liquid

Answer: (D) Decrease in viscosity of liquid


Q2. Liquids transmit pressure equally in all the directions. This is according to

(A) Boyle’s law
(B) Archimedes principle
(C) Pascal’s law
(D) Newton’s formula

Answer: (C) Pascal’s law


Q3. A pipe of length more than double the diameter of orifice fitted externally or internally to the orifice is called a

(A) Notch
(B) Weir
(C) Mouthpiece
(D) Nozzle

Answer: (C) Mouthpiece


Q4. Euler’s number is the ratio of __ force to pressure force.

(A) Inertia
(B) Gravity
(C) Viscous
(D) None of these

Answer: (A) Inertia


Q5. The discharge through a channel of trapezoidal section is maximum when

(A) Width of channel at the top is equal to twice the width at the bottom
(B) Depth of channel is equal to the width at the bottom
(C) The sloping side is equal to half the width at the top
(D) The sloping side is equal to the width at the bottom

Answer: (C) The sloping side is equal to half the width at the top


Q6. The bulk modulus of elasticity

(A) Has the dimensions of 1/pressure
(B) Increases with pressure
(C) Is large when fluid is more compressible
(D) Is independent of pressure and viscosity

Answer: (B) Increases with pressure


Q7. A jet of water discharging from a 40 mm diameter orifice has a diameter of 32 mm at its vena contracta. The coefficient of contraction is

(A) 0.46
(B) 0.64
(C) 0.78
(D) 0.87

Answer: (B) 0.64


Q8. The difference of pressure between the inside and outside of a liquid drop is

(A) p = T × r
(B) p = T/r
(C) p = T/2r
(D) p = 2T/r

Answer: (D) p = 2T/r


Q9. The length AB of a pipe ABC in which the liquid is flowing has diameter (d1) and is suddenly contracted to diameter (d2) at B which is constant for the length BC. The loss of head due to sudden contraction, assuming coefficient of contraction as 0.62, is

(A) v₁²/2g
(B) v₂²/2g
(C) 0.5 v₁²/2g
(D) 0.375 v₂²/2g

Answer: (D) 0.375 v₂²/2g


Q10. The force per unit length is the unit of

(A) Surface tension
(B) Compressibility
(C) Capillarity
(D) Viscosity

Answer: (A) Surface tension


Q11. The coefficient of discharge for an external mouthpiece depends upon

(A) Velocity of liquid
(B) Pressure of liquid
(C) Area of mouthpiece
(D) Length of mouthpiece

Answer: (D) Length of mouthpiece


Q12. A flow in which __ force is dominating over the viscosity is called turbulent flow.

(A) Elastic
(B) Surface tension
(C) Viscous
(D) Inertia

Answer: (D) Inertia


Q13. The tangential velocity of the water element having a free vortex is

(A) Directly proportional to its distance from the centre
(B) Inversely proportional to its distance from the centre
(C) Directly proportional to its (distance)2 from the centre
(D) Inversely proportional to its (distance)2 from the centre

Answer: (B) Inversely proportional to its distance from the centre


Q14. A structure used to dam up a stream or river over which the water flows is called

(A) Orifice
(B) Notch
(C) Weir
(D) Dam

Answer: (C) Weir


Q15. The discharge through a small rectangular orifice is given by (where Cd = Coefficient of discharge for the orifice, a = Cross-sectional area of the orifice, h = Height of the liquid above the centre of the orifice)

(A) Q = Cd × a × 2gh
(B) Q = (2/3). Cd × a × h
(C) Q = (Cd × a)/√(2gh)
(D) Q = (3Cd × a)/√(2h)

Answer: (A) Q = Cd × a × 2gh


Q16. In order to measure the flow with a Venturimeter, it is installed in

(A) Horizontal line
(B) Inclined line with flow upwards
(C) Inclined line with flow downwards
(D) Any direction and in any location

Answer: (D) Any direction and in any location


Q17. In a short cylindrical external mouthpiece, the vena contracta occurs at a distance __ the diameter of the orifice from the outlet of orifice.

(A) Equal to
(B) One-fourth
(C) One-third
(D) One-half

Answer: (B) One-fourth


Q18. Which of the following is an example of laminar flow?

(A) Underground flow
(B) Flow past tiny bodies
(C) Flow of oil in measuring instruments
(D) All of these

Answer: (D) All of these


Q19. The discharge over a triangular notch is

(A) Inversely proportional to H3/2
(B) Directly proportional to H3/2
(C) Inversely proportional to H5/2
(D) Directly proportional to H5/2

Answer: (D) Directly proportional to H5/2


Q20. An open tank containing liquid is moving with an acceleration on an inclined plane. The inclination of the free surface of the liquid will be __ to the acceleration of the tank.

(A) Equal to
(B) Directly proportional
(C) Inversely proportional
(D) None of these

Answer: (B) Directly proportional


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