Fluid Mechanics MCQs

Question 1

In an incompressible flow of fluid, the fluid

Accepted Answer

Density does not change with pressure & temperature

Answer

Temperature remains constant

Answer

Compressibility is greater than zero

Answer

Is frictionless

Question 2

The dimension of kinematic viscosity is

Accepted Answer

L2T-1

Answer

ML-2T-1

Answer

ML-2T-2

Answer

None of these

Question 3

Dimension of kinematic viscosity is

Accepted Answer

L2T-1

Answer

MLT-1

Answer

L2T

Answer

L2T-2

Question 4

The drag co-efficient for a bacterium moving in water at 1 mm/s, will be of the following order of magnitude (assume size of the bacterium to be 1 micron and kinematic viscosity of water to be 10-6 m2/s).

Accepted Answer

0.44

Answer

24000

Answer

24

Answer

0.24

Question 5

The ratio of hydrodynamic boundary layer to thermal boundary layer thickness in case of liquid metals is

Accepted Answer

< 1

Answer

1

Answer

> 1

Answer

2

Question 6

The hydraulic radius for flow in a rectangular duct of cross-sectional dimension H, W is

Accepted Answer

$$\frac{{{	ext{HW}}}}{{2{{\left( {{	ext{H}} + {	ext{W}}} ight)}^2}}}$$

Answer

$$\sqrt {\frac{{{	ext{HW}}}}{\pi }} $$

Answer

$$\frac{{{	ext{HW}}}}{{4{{\left( {{	ext{H}} + {	ext{W}}} ight)}^2}}}$$

Answer

$$\frac{{2{	ext{HW}}}}{{\left( {{	ext{H}} + {	ext{W}}} ight)}}$$

Question 7

For water, when the pressure increases, the viscosity

Accepted Answer

First decreases, and then increases

Answer

Also increases

Answer

Decreases

Answer

Remains constant

Question 8

Boundary layer thickness in laminar flow over a flat plate increases as (where, d = distance from the leading edge.)

Accepted Answer

$$\sqrt {	ext{d}} $$

Answer

$${{	ext{d}}^{\frac{1}{3}}}$$

Answer

d2

Answer

$${{	ext{d}}^{\frac{2}{3}}}$$

Question 9

Boundary layer thickness in turbulent flow over a flat plate increases as (where, d = distance from the leading edge.)

Accepted Answer

$${{	ext{d}}^{\frac{4}{5}}}$$

Answer

$$\sqrt {	ext{d}} $$

Answer

$${{	ext{d}}^{\frac{2}{3}}}$$

Answer

$${{	ext{d}}^{\frac{1}{3}}}$$