# 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

## 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

## 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)

## 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

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

## 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

## 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

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

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

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

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

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

## 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

## Q19. Kinematic viscosity is equal to

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