Hydraulic Machines-Fluid Machineries – Set 12

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Q1. The flow in a pipe or channel is said to be non-uniform when

(A) The liquid particles at all sections have the same velocities
(B) The liquid particles at different sections have different velocities
(C) The quantity of liquid flowing per second is constant
(D) Each liquid particle has a definite path

Answer: (B) The liquid particles at different sections have different velocities


Q2. Select the correct statement

(A) Local atmospheric pressure depends upon elevation of locality only
(B) Standard atmospheric pressure is the mean local atmospheric pressure a* sea level
(C) Local atmospheric pressure is always below standard atmospheric pressure
(D) A barometer reads the difference between local and standard atmospheric pressure

Answer: (B) Standard atmospheric pressure is the mean local atmospheric pressure a* sea level


Q3. 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/Ax̅) – x̅
(B) (IG/x̅) – Ax̅
(C) (Ax̅/IG) + x̅
(D) (IG/Ax̅) + x̅

Answer: (D) (IG/Ax̅) + x̅


Q4. A liquid compressed in cylinder has a volume of 0.04 m3 at 50 kg/cm² and a volume of 0.039 m3 at 150 kg/cm². The bulk modulus of elasticity of liquid is

(A) 400 kg/cm²
(B) 4000 kg/cm²
(C) 40 × 10⁵ kg/cm²
(D) 40 × 10⁶ kg/cm²

Answer: (B) 4000 kg/cm²


Q5. Select the correct statement

(A) Weber’s number is the ratio of inertia force to elastic force
(B) Weber’s number is the ratio of gravity force to surface tension force
(C) Weber’s number is the ratio of viscous force to pressure force
(D) Weber’s number is the ratio of inertia force to surface tension force

Answer: (D) Weber’s number is the ratio of inertia force to surface tension force


Q6. For a body floating in a liquid the normal pressure exerted by the liquid acts at

(A) Bottom surface of the body
(B) C.G. of the body
(C) Metacenter
(D) All points on the surface of the body

Answer: (D) All points on the surface of the body


Q7. The flow in a pipe is neither laminar nor turbulent when Reynold number is

(A) Less than 2000
(B) Between 2000 and 2800
(C) More than 2800
(D) None of these

Answer: (B) Between 2000 and 2800


Q8. The discharge through a convergent mouthpiece is __ the discharge through an internal mouthpiece of the same diameter and head of water.

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

Answer: (D) Double


Q9. Capillary action is due to the

(A) Surface tension
(B) Cohesion of the liquid
(C) Adhesion of the liquid molecules and the molecules on the surface of a solid
(D) All of the above

Answer: (D) All of the above


Q10. Reynold’s number is the ratio of inertia force to

(A) Pressure force
(B) Elastic force
(C) Gravity force
(D) Viscous force

Answer: (D) Viscous force


Q11. Choose the wrong statement

(A) The center of buoyancy is located at the center of gravity of the displaced liquid
(B) For stability of a submerged body, the center of gravity of body must lie directly below the center of buoyancy
(C) If C.G. and center of buoyancy coincide, the submerged body must lie at neutral equilibrium for all positions
(D) All floating bodies are stable

Answer: (D) All floating bodies are stable


Q12. The power transmitted through a pipe is (where w = Specific weight in N/m3, and Q = Discharge in m3/s)

(A) w × Q × H
(B) w × Q × hf
(C) w × Q (H – hf)
(D) w × Q (H + hf)

Answer:(C) w × Q (H – hf)


Q13. Cavitation will begin when

(A) The pressure at any location reaches an absolute pressure equal to the saturated vapour pressure of the liquid
(B) Pressure becomes more than critical pressure
(C) Flow is increased
(D) Pressure is increased

Answer: (A) The pressure at any location reaches an absolute pressure equal to the saturated vapour pressure of the liquid


Q14. The flow in which each liquid particle has a definite path and their paths do not cross each other is called

(A) One dimensional flow
(B) Streamline flow
(C) Steady flow
(D) Turbulent flow

Answer: (B) Streamline flow


Q15. The viscosity of water is __ than that of mercury.

(A) Higher
(B) Lower
(C) Same as
(D) None of these

Answer: (A) Higher


Q16. The bulk modulus of elasticity with increase in pressure

(A) Increases
(B) Decreases
(C) Remain constant
(D) Increases first up to certain limit and then decreases

Answer: (A) Increases


Q17. When the flow in an open channel is gradually varied, the flow is said to be

(A) Steady uniform flow
(B) Steady non-uniform flow
(C) Unsteady uniform flow
(D) Unsteady non-uniform flow

Answer: (B) Steady non-uniform flow


Q18. Hydrometer is used to determine

(A) Specific gravity of liquids
(B) Specific gravity of solids
(C) Specific gravity of gases
(D) Relative humidity

Answer: (A) Specific gravity of liquids


Q19. The shear stress-strain graph for a Newtonian fluid is a

(A) Straight line
(B) Parabolic curve
(C) Hyperbolic curve
(D) Elliptical

Answer:(A) Straight line


Q20. Mach number is significant in

(A) Supersonics, as with projectiles and jet propulsion
(B) Full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.
(C) Simultaneous motion through two fluids where there is a surface of discontinuity, gravity force, and wave making effects, as with ship’s hulls
(D) All of the above

Answer: (A) Supersonics, as with projectiles and jet propulsion


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