Hydraulics and Fluid Mechanics MCQ – Set 18

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Q1. A flow in which the volume of a fluid and its density does not change during the flow is called _ flow.

(A) Incompressible
(B) Compressible
(C) Viscous
(D) None of these

Answer: (A) Incompressible


Q2. Piezometer is used to measure

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

Answer: (C) Very low pressures


Q3. A tank of uniform cross-sectional area (A) containing liquid upto height (H1) has an orifice of cross-sectional area (a) at its bottom. The time required to empty the tank completely will be

(A) (2A√H₁)/(Cd × a√2g)
(B) (2AH₁)/(Cd × a√2g)
(C) (2AH₁3/2)/(Cd × a√2g)
(D) (2AH₁²)/(Cd × a√2g)

Answer:(A) (2A√H₁)/(Cd × a√2g)


Q4. Buoyant force is

(A) Resultant force acting on a floating body
(B) Equal to the volume of liquid displaced
(C) Force necessary to keep a body in equilibrium
(D) The resultant force on a body due to the fluid surrounding it

Answer: (D) The resultant force on a body due to the fluid surrounding it


Q5. A venturi-flume is used to measure

(A) Pressure of liquid
(B) Discharge of liquid
(C) Pressure difference between two points in a channel
(D) Pressure difference between two points in a pipe

Answer: (B) Discharge of liquid


Q6. Operation of McLeod gauge used for low pressure measurement is based on the principle of

(A) Gas law
(B) Boyle’s law
(C) Charles law
(D) Pascal’s law

Answer: (B) Boyle’s law


Q7. When the Mach number is more than 6, the flow is called

(A) Sub-sonic flow
(B) Sonic flow
(C) Super-sonic flow
(D) Hyper-sonic flow

Answer: (D) Hyper-sonic flow


Q8. Specific weight of sea water is more that of pure water because it contains

(A) Dissolved air
(B) Dissolved salt
(C) Suspended matter
(D) All of the above

Answer: (D) All of the above


Q9. The horizontal component of buoyant force is

(A) Negligible
(B) Same as buoyant force
(C) Zero
(D) None of the above

Answer: (C) Zero


Q10. A body floating in a liquid is said to be in neutral equilibrium, if its metacentre

(A) Coincides with its centre of gravity
(B) Lies above its centre of gravity
(C) Lies below its centre of gravity
(D) Lies between the centre of buoyancy and centre of gravity

Answer: (A) Coincides with its centre of gravity


Q11. When a body is placed over a liquid, it will float 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:(B) Gravitational force is less than the up-thrust of the liquid


Q12. If mercury in a barometer is replaced by water, the height of 3.75 cm of mercury will be following cm of water

(A) 51 cm
(B) 50 cm
(C) 52 cm
(D) 52.2 cm

Answer: (A) 51 cm


Q13. A submerged body is said to be in a stable equilibrium, if its centre of gravity __ the centre of buoyancy.

(A) Coincides with
(B) Lies below
(C) Lies above
(D) None of these

Answer: (B) Lies below


Q14. Re-entrant or Borda’s mouthpiece is an __ mouthpiece.

(A) Internal
(B) External
(C) Both A and B
(D) None of these

Answer: (A) Internal


Q15. A flow whose streamline is represented by a straight line, is called __ dimensional flow.

(A) One
(B) Two
(C) Three
(D) Four

Answer: (A) One


Q16. The coefficient of discharge for an external mouthpiece is

(A) 0.375
(B) 0.5
(C) 0.707
(D) 0.855

Answer: (D) 0.855


Q17. The weight per unit volume of a liquid at a standard temperature and pressure is called

(A) Specific weight
(B) Mass density
(C) Specific gravity
(D) None of these

Answer: (A) Specific weight


Q18. The point at which the resultant pressure on an immersed surface acts, is known as

(A) Centre of gravity
(B) Centre of depth
(C) Centre of pressure
(D) Centre of immersed surface

Answer: (C) Centre of pressure


Q19. Kinematic viscosity is equal to

(A) Dynamic viscosity/density
(B) Dynamic viscosity × density
(C) Density/dynamic viscosity
(D) 1/dynamic viscosity × density

Answer: (A) Dynamic viscosity/density


Q20. In case of flow through parallel pipes,

(A) The head loss for all the pipes is same
(B) The total discharge is equal to the sum of discharges in the various pipes
(C) The total head loss is the sum of head losses in the various pipes
(D) Both (A) and (B)

Answer: (D) Both (A) and (B)


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