Hydraulics and Fluid Mechanics MCQ – Set 01

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Q1. When a body is placed over a liquid, it will sink down if

(A) Gravitational force is equal to the up-thrust of the liquid
(B) Gravitational force is less than the up-thrust of the liquid
(C) Gravitational force is more than the up-thrust of the liquid
(D) None of the above

Answer: (C) Gravitational force is more than the up-thrust of the liquid


Q2. A fluid which obeys the Newton’s law of viscosity is termed as

(A) Real fluid
(B) Ideal fluid
(C) Newtonian fluid
(D) Non-Newtonian fluid

Answer: (C) Newtonian fluid


Q3. A fluid in equilibrium can’t sustain

(A) Tensile stress
(B) Compressive stress
(C) Shear stress
(D) Bending stress

Answer: (C) Shear stress


Q4. When a tank containing liquid moves with an acceleration in the horizontal direction, then the free surface of the liquid

(A) Remains horizontal
(B) Becomes curved
(C) Falls on the front end
(D) Falls on the back end

Answer: (C) Falls on the front end


Q5. Differential manometer is used to measure

(A) Pressure in pipes, channels etc.
(B) Atmospheric pressure
(C) Very low pressure
(D) Difference of pressure between two points

Answer:(D) Difference of pressure between two points


Q6. Stoke is the unit of

(A) Kinematic viscosity in C. G. S. units
(B) Kinematic viscosity in M. K. S. units
(C) Dynamic viscosity in M. K. S. units
(D) Dynamic viscosity in S. I. units

Answer: (A) Kinematic viscosity in C. G. S. units


Q7. The depth of center of pressure of an immersed surface, inclined at an angle ‘θ’ with the liquid surface lies at a distance equal to __ the center of gravity.

(A) IG sin²θ/Ax̅ bellow
(B) IG sin²θ/Ax̅ above
(C) IG sinθ/Ax̅ bellow
(D) IG sinθ/Ax̅ above

Answer:(A) IG sin²θ/Ax̅ bellow


Q8. Free surface of a liquid behaves like a sheet and tends to contract to smallest possible area due to the

(A) Force of adhesion
(B) Force of cohesion
(C) Force of friction
(D) Force of diffusion

Answer: (B) Force of cohesion


Q9. In a footstep bearing, if the speed of the shaft is doubled, then the torque required to overcome the viscous resistance will be

(A) Double
(B) Four times
(C) Eight times
(D) Sixteen times

Answer: (A) Double


Q10. True one-dimensional flow occurs when

(A) The direction and magnitude of the velocity at all points are identical
(B) The velocity of successive fluid particles, at any point, is the same at successive periods of time
(C) The magnitude and direction of the velocity do not change from point to point in the fluid
(D) The fluid particles move in plane or parallel planes and the streamline patterns are identical in each plane

Answer: (A) The direction and magnitude of the velocity at all points are identical


Q11. A compound pipe is required to be replaced by a new pipe. The two pipes are said to be equivalent, if

(A) Length of both the pipes is same
(B) Diameter of both the pipes is same
(C) Loss of head and discharge of both the pipes is same
(D) Loss of head and velocity of flow in both the pipes is same

Answer: (C) Loss of head and discharge of both the pipes is same


Q12. Metacentric height is the distance between the metacentre and

(A) Water surface
(B) Center of pressure
(C) Center of gravity
(D) Center of buoyancy

Answer: (C) Center of gravity


Q13. The fluid forces considered in the Navier Stokes equation are

(A) Gravity, pressure and viscous
(B) Gravity, pressure and turbulent
(C) Pressure, viscous and turbulent
(D) Gravity, viscous and turbulent

Answer: (A) Gravity, pressure and viscous


Q14. The specific weight of sea water is __ that of pure water.

(A) Same as
(B) Less than
(C) More than
(D) None of these

Answer: (C) More than


Q15. Free surface of a liquid tends to contract to the smallest possible area due to force of

(A) Surface tension
(B) Viscosity
(C) Friction
(D) Cohesion

Answer: (A) Surface tension


Q16. In an internal mouthpiece, if the jet after contraction does not touch the sides of the mouthpiece, then the mouthpiece is said to be

(A) Running full
(B) Running free
(C) Partially running full
(D) Partially running free

Answer: (B) Running free


Q17. For pipes, turbulent flow occurs when Reynolds number is

(A) Less than 2000
(B) Between 2000 and 4000
(C) More than 4000
(D) Less than 4000

Answer: (C) More than 4000


Q18. The property by virtue of which a liquid opposes relative motion between its different layers is called

(A) Surface tension
(B) Coefficient of viscosity
(C) Viscosity
(D) Osmosis

Answer: (C) Viscosity


Q19. In order that flow takes place between two points in a pipeline, the differential pressure between these points must be more than

(A) Frictional force
(B) Viscosity
(C) Surface friction
(D) All of the above

Answer: (D) All of the above


Q20. When a plate is immersed in a liquid parallel to the flow, it will be subjected to a pressure __ that if the same plate is immersed perpendicular to the flow.

(A) Less than
(B) More than
(C) Equal to
(D) None of these

Answer: (A) Less than


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