Multiple choice questions (MCQ) on Fluid mechanics

1. The square root of the ratio of inertia force to gravity force is called

a. Reynolds number      b. Froude number          c. Mach number                        d. Euler number


2. The thickness of turbulent boundary layer at a distance x from the leading edge over a flat plate varies as

a. x4/5                b. x1/2                c. x1/5                d. x3/5


3. The Bernoulli’s equation refers to conservation of

a. mass                                                b. linear momentum

c. angular momentum                  d. energy


4. In a normal shock wave in one dimensional flow

a. pressure, density and temperature increase                       b. velocity, temperature and density increase

c. pressure, density and temperature decrease                      d. velocity, pressure and density decrease


5. The drag coefficient for laminar flow varies with Reynolds number (Re) as

a. Re1/2              b. Re                            c. Re-1                           d. Re-1/2


6. The continuity equation in a differential form is

a. dA/A + dV/V + dρ/ρ = constant                                  b. A/dA + V/dV + ρ/dρ = constant

c. dA/A + dV/V + dρ/ρ = 0                                             d. AdA + VdV + ρdρ = 0


7. What is the percentage error in the estimation of the discharge due to an error of 2% in the measurement of the reading of a differential manometer connected to an orifice meter?

a. 4                   b. 3                  c. 2                   d. 1


8. Which one of the following is the characteristic of a fully developed laminar flow?

a. The pressure drop in the flow direction is zero

b. The velocity profile changes uniformly in the flow direction

c. The velocity profile does not change in the flow direction

d. The Reynolds number for the flow is critical


9. A circular plate of 1.5 m diameter is submerged in water with its greatest and least depths below the water surface being 2 m and 0.75 m respectively, what is the approximate magnitude of the total thrust on one face of the plate?

a. 24Kn             b. 28kN             c. 12kN             d. 16kN


10. Which of the following statements is correct?

A steady flow of diverging straight stream lines

a. is a uniform flow with local acceleration                            b. has convective normal acceleration

c. has convective tangential acceleration                              d. has both convective normal and tangential accelerations


11. Bernoulli’s theorem P/ρg + V2/2g = constant is valid

a. along different streamlines in rotational flow                   b. along different streamlines in irrotational flow

c. only in the case of flow of gas                                                  d. only in the case of flow of liquid


12. Two pipelines of equal lengths are connected in series. The diameter of the second pipe is two times that of the first pipe. The ratio of frictional head losses between the first pipe and the second pipe is

a. 1:32              b. 1:16              c. 1:8                d. 1:4


13. The following instruments are used in the measurement of discharge through a pipe:

1. Orifice meter                        2. Flow nozzle              3. Venturimeter

a. 1, 3, 2           b. 1, 2, 3           c. 3, 2, 1           d 2, 3, 1


14. If a fluid jet discharging from a 50 mm diameter orifice has a 40 mm diameter at its vena contracta, then its coefficient of contraction will be

a. 0.32              b. 0.64              c. 0.96              d. 1.64


15. Boundary layer separation is caused by

a. reduction of pressure below vapour pressure                        b. reduction of pressure gradient to zero

c. an adverse pressure gradient                                             d. reduction of boundary layer to zero thickness


16. The velocity distribution in laminar flow through a circular pipe follows the

a. linear law                   b. parabolic                  c. cubic power law         d. logarithmic law


17. Fluids that require a gradually increasing shear stress to maintain a constant strain rate are known as

a. rhedopectic fluids                  b. thixotropic fluids       c. pseudoplastic fluids              d. Newtonian fluids


18. The fraction of the volume of a solid piece of metal of relative density 8.25 floating above the surface of a container of mercury of relative density 13.6 is

a. 1.648            b. 0.607            c. 0.393                        d. 0.352


19. An instrument which offers no obstruction to the flow, offers no additional loss and is suitable for flow measurement is

a. Venturimeter                          b. Rotameter                 c. Magnetic flow meter              d. Bend meter


20. The minimum value of friction factor ‘f’ that can occur in laminar flow through a circular pipe is:

a. 0.064            b. 0.032            c. 0.016                        d. 0.008