Fluid Mechanics, Hydraulics and Hydrology MCQ (NEC Chapter 3 Water Resources)

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Chapter 3: Fluid Mechanics, Hydraulics and Hydrology MCQ

233 questions with answers. Practise by sub-section or take a timed test.

Chapter

Sub-section

LevelAll questionsSub-engineer level2-mark questions only

Number of questions102550All

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Free practice by EngineeringNepal.com.np. Questions are written and checked by our team; always confirm the current exam format in the official notice.

Fluid Mechanics, Hydraulics and Hydrology MCQ: what this set covers

This chapter covers the basic water resources part of the syllabus: properties of fluids, pressure and buoyancy, the continuity and Bernoulli equations, losses in pipes, open channel flow and hydraulic jump, and hydrology from rainfall to flood frequency.

There are 233 questions in this chapter, each with the answer and a short explanation. Choose a sub-section, pick how many questions you want, and either see the answer straight away or take it as a timed test. Your mistakes are saved in your browser, so you can come back and practise only those.

Code	Sub-section	Questions here
3.1	Fluid properties	32
3.2	Hydrostatics	32
3.3	Fluid kinematics and dynamics	32
3.4	Pipe flow	32
3.5	Open channel flow	32
3.6	Hydrology	32

Sample questions with answers

A few questions from each sub-section are shown below. Tap a question to see the answer. Use the practice tool above for the full set.

3.1 Fluid properties

The SI unit of dynamic (absolute) viscosity is:

1. m²/s
2. kg/m³
3. N·s/m²
4. N/m

Answer: C. From τ = μ du/dy, μ = τ/(du/dy) has units (N/m²)/(1/s) = N·s/m², which is the same as Pa·s.

Kinematic viscosity of a fluid is defined as the:

1. Ratio of dynamic viscosity to mass density
2. Product of dynamic viscosity and mass density
3. Ratio of mass density to dynamic viscosity
4. Ratio of shear stress to velocity

Answer: A. ν = μ/ρ, with SI unit m²/s. It contains no force unit, hence the name kinematic.

3.2 Hydrostatics

Pascal's law for a fluid at rest states that:

1. Pressure at a point acts only vertically downward
2. Pressure increases linearly with velocity
3. Pressure at a point is equal in all directions
4. Pressure is inversely proportional to volume

Answer: C. In a static fluid there is no shear stress, so the normal stress at a point is the same on every plane through it.

Taking the unit weight of water as 10 kN/m³, the gauge pressure at a depth of 5 m below the free surface of still water is:

1. 50 kPa
2. 5 kPa
3. 500 kPa
4. 0.5 kPa

Answer: A. p = γh = 10 × 5 = 50 kN/m² = 50 kPa.

3.3 Fluid kinematics and dynamics

A flow is said to be steady when, at any given point in the flow:

1. Velocity does not change from point to point
2. Fluid particles move in parallel layers
3. Flow properties do not change with time
4. Density is the same everywhere

Answer: C. Steady flow means ∂/∂t of velocity, pressure, density etc. is zero at every fixed point. Unchanging velocity along the flow (in space) is uniform flow, a different idea.

Water flows at a constant rate through a tapering pipe. The flow is:

1. Steady and non-uniform
2. Steady and uniform
3. Unsteady and uniform
4. Unsteady and non-uniform

Answer: A. The discharge does not change with time (steady), but the velocity changes from section to section as the area reduces (non-uniform).

3.4 Pipe flow

Water (kinematic viscosity 1 × 10⁻⁶ m²/s) flows at 1 m/s in a pipe of 100 mm diameter. The Reynolds number is:

1. 10,000
2. 1,000,000
3. 100,000
4. 1,000

Answer: C. Re = VD/ν = 1 × 0.1 / 10⁻⁶ = 100,000, so the flow is turbulent.

Flow in a circular pipe is normally laminar when the Reynolds number is below about:

1. 2000
2. 4000
3. 500
4. 10000

Answer: A. Pipe flow is laminar below about 2000, transitional between about 2000 and 4000, and turbulent above about 4000.

3.5 Open channel flow

The main feature that distinguishes open channel flow from pipe flow is that open channel flow:

1. Always flows full under pressure
2. Has a uniform velocity over the section
3. Has a free surface at atmospheric pressure
4. Is always laminar

Answer: C. Open channel flow is driven by gravity and has a free surface; a pipe running partly full (like a sewer) is also open channel flow.

A rectangular channel 4 m wide carries water 1 m deep. Its hydraulic radius is:

1. 0.67 m
2. 1.0 m
3. 0.5 m
4. 0.8 m

Answer: A. A = 4 × 1 = 4 m², P = 4 + 2 × 1 = 6 m, so R = A/P = 4/6 = 0.67 m.

3.6 Hydrology

The hydrologic cycle is driven mainly by:

1. Wind alone
2. The Earth's rotation
3. Solar energy and gravity
4. Tidal forces

Answer: C. Solar energy evaporates water and lifts it into the atmosphere; gravity brings it back as precipitation, runoff and infiltration.

Heavy monsoon rainfall on the windward southern slopes of Nepal's hills, when moist air is forced to rise over the mountains, is mainly:

1. Orographic precipitation
2. Convective precipitation
3. Frontal (cyclonic) precipitation
4. Drizzle

Answer: A. When moist air is lifted by a mountain barrier it cools adiabatically and condenses, giving orographic rain on the windward side and a rain shadow on the leeward side.

Full mock tests

When you have covered every chapter, take a full NEC licence mock test or Lok Sewa model test. The NEC mock follows the current NEC pattern of 100 one-mark questions in 2 hours, the format used in the model question sets NEC published in November 2025.

Other chapters

• Ch 1: Basic Civil Engineering
• Ch 2: Soil Mechanics and Foundation Engineering
• Ch 4: Structural Mechanics
• Ch 5: Design of Structures
• Ch 6: Water Supply, Sanitation and Environment
• Ch 7: Irrigation and Drainage
• Ch 8: Hydropower Engineering
• Ch 9: Transportation Engineering
• Ch 10: Project Planning, Design and Implementation
• Lok Sewa extra topics

See also: NEC civil licence syllabus, Lok Sewa civil engineer syllabus and the NEC licence exam guide.