A venturi meter is used to measure fluid flow rate. The principle it operates on is:

The correct answer is B: Continuity equation and Bernoulli's equation. Venturi meter uses both continuity equation (conservation of mass) and Bernoulli's equation (energy conservation) to relate pressure difference to flow velocity.

For flow through an orifice, the discharge coefficient Cd is always:

The correct answer is C: Less than 1. Cd < 1 accounts for vena contracta and frictional losses in actual orifice flow compared to ideal flow.

A rolling contact bearing has an equivalent dynamic load of 8 kN and a rating life of 10,000 hours at 1500 RPM. Which bearing parameter is most affected by speed and load combination?

The correct answer is B: L10 life in revolutions. The L10 life (in revolutions) is directly affected by both the equivalent dynamic load and speed according to the bearing life equation: L₁₀ = (C/P)³ × 10⁶

A reversible isothermal process occurs at 300 K for an ideal gas. If 5 kJ of heat is absorbed, what is the change in entropy of the system?

The correct answer is A: 16.67 J/K. For isothermal process: ΔS = Q/T = 5000/300 = 16.67 J/K. Change in entropy is positive as heat is absorbed.

A piston-cylinder device contains 0.5 kg of steam at 200°C. Heat is removed and the steam condenses to saturated liquid at the same temperature. The latent heat of vaporization at 200°C is 1941 kJ/kg. Calculate heat removed.

The correct answer is A: 970.5 kJ. Q = m × L_fg = 0.5 kg × 1941 kJ/kg = 970.5 kJ heat is removed during condensation

Home

Home › Subjects › Mechanical Engineering › Fluid Mechanics

Mechanical Engineering
Fluid Mechanics

Thermodynamics, hydraulics, machine design

19 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 19

Topics in Mechanical Engineering

All Thermodynamics 100 Fluid Mechanics 79 Machine Design 80

Q.1 Hard Fluid Mechanics

The cavitation parameter σ = (P - Pv)/(0.5ρV²) indicates the tendency of a flowing fluid to cavitate. Cavitation occurs when σ drops below a critical value σc. For a given pump, lowering the inlet pressure or raising the fluid temperature will:

A Increase σ and reduce cavitation risk

B Decrease σ and increase cavitation risk

C Keep σ constant

D Increase Pv but not affect cavitation

Correct Answer: B. Decrease σ and increase cavitation risk

EXPLANATION

Lowering inlet pressure decreases (P - Pv), reducing σ. Raising temperature increases Pv, also reducing σ. Both conditions increase cavitation risk in turbomachinery. This is critical in high-speed pump operations.

Test

Q.2 Hard Fluid Mechanics

According to the theory of boundary layer flow, the boundary layer thickness δ grows along a flat plate as δ ∝ √(νx/V). This relationship is derived from:

A Euler's equation

B Prandtl's momentum integral equation

C Navier-Stokes equations with boundary layer approximations

D Continuity equation alone

Correct Answer: C. Navier-Stokes equations with boundary layer approximations

EXPLANATION

The √x dependence comes from solving the Navier-Stokes equations with boundary layer approximations (Blasius solution). This is fundamental to aerodynamic design in Indian aircraft industries.

Test

Q.3 Hard Fluid Mechanics

The specific speed of a turbine is Ns = N√Q/H^1.25, where N is speed in rpm, Q is discharge in m³/s, and H is head in meters. A turbine with Ns < 50 is classified as:

A Pelton turbine (impulse)

B Turgo turbine

C Francis turbine (reaction)

D Kaplan turbine (axial flow)

Correct Answer: A. Pelton turbine (impulse)

EXPLANATION

Specific speed Ns < 50 indicates Pelton turbines, 50-250 indicates Francis turbines, and >250 indicates Kaplan turbines. This classification is essential in hydroelectric projects across Indian dams.

Test

Q.4 Hard Fluid Mechanics

For pipe flow, the friction factor f in the Moody diagram depends on both Reynolds number and relative roughness (ε/D). For a rough pipe with high Re, f approaches an asymptotic value independent of Re. This region is called:

A Laminar region

B Fully turbulent region (complete turbulence)

C Transition region

D Creeping flow region

Correct Answer: B. Fully turbulent region (complete turbulence)

EXPLANATION

At very high Reynolds numbers in rough pipes, friction factor depends only on relative roughness, not Re. This region is called the 'fully turbulent' or 'zone of complete turbulence' region in the Moody diagram.

Test

Q.5 Hard Fluid Mechanics

The Mach number M = V/a represents the ratio of flow velocity to the speed of sound. For subsonic compressible flow in a converging nozzle, what occurs to the Mach number as the flow accelerates?

A Mach number decreases

B Mach number remains constant

C Mach number increases

D Mach number becomes negative

Correct Answer: C. Mach number increases

EXPLANATION

In a converging nozzle with subsonic inlet flow, velocity increases and Mach number increases as flow approaches throat. This principle is critical in rocket propulsion and aerospace applications in India.

Test

Q.6 Hard Fluid Mechanics

For a Venturi tube with throat area ratio A₁/A₂ = 3 and upstream pressure P₁ = 200 kPa, assuming inviscid flow (Bernoulli applicable), if the pressure at throat P₂ drops to 80 kPa, the upstream velocity V₁ is (ρ = 1000 kg/m³):

A 6.5 m/s

B 8.2 m/s

C 10.5 m/s

D 12.8 m/s

Correct Answer: C. 10.5 m/s

EXPLANATION

From Bernoulli: P₁/ρg + V₁²/2g = P₂/ρg + V₂²/2g. Using continuity A₁V₁ = A₂V₂, and solving: V₁ = √(2(P₁-P₂)/(ρ(A₂²/A₁²-1))) ≈ 10.5 m/s. Venturi tubes are standard in flow measurement systems.

Test

Q.7 Hard Fluid Mechanics

The momentum equation for a control volume states that ΣF = d(mV)/dt. For a fluid jet deflected by a flat plate at angle θ to the horizontal, the force perpendicular to the original jet direction depends on:

A Only the jet velocity

B Only the deflection angle

C Both jet velocity and deflection angle (sinθ component)

D The density of the fluid only

Correct Answer: C. Both jet velocity and deflection angle (sinθ component)

EXPLANATION

The perpendicular force component = ρQV²sin(θ), where Q is discharge and V is velocity. This principle is used in water turbines and industrial jet applications.

Test

Q.8 Hard Fluid Mechanics

A horizontal jet of 0.02 m² cross-section with velocity 8 m/s strikes a curved vane and is deflected 60°. What is the force on the vane in the direction of jet?

A 10.24 kN

B 12.80 kN

C 6.40 kN

D 5.12 kN

Correct Answer: C. 6.40 kN

EXPLANATION

Force = ρAV²(1 - cos60°) = 1000 × 0.02 × 64 × 0.5 = 6.4 kN. The deflection angle affects the force component.

Test

Q.9 Hard Fluid Mechanics

In a venturi meter, if the area ratio is 4:1 and the pressure difference is 8 kPa, what is the velocity in the throat? (ρ_water = 1000 kg/m³)

A 2.06 m/s

B 4.12 m/s

C 6.18 m/s

D 8.24 m/s

Correct Answer: B. 4.12 m/s

EXPLANATION

From Bernoulli and continuity: V₂ = √(2ΔP/(ρ(A₁²/A₂² - 1))) = √(16000/(1000 × 15)) = 4.12 m/s

Test

Q.10 Hard Fluid Mechanics

A circular jet impinges on a 45° inclined flat plate and splits equally. If jet velocity is 15 m/s and diameter is 30 mm, what is the magnitude of the resultant force?

A 2650 N

B 2074 N

C 2648 N

D 1874 N

Correct Answer: C. 2648 N

EXPLANATION

Using momentum equation with 45° deflection, the resultant force = ρAV² × √2 = 1000 × 0.000707 × 225 × 1.414 = 2648 N

Test

1 2

All Subjects & Topics

Govt. Exams

Entrance Exams

Teacher Exams

Subjects

Quick Links

Mechanical Engineering Fluid Mechanics

Mechanical Engineering
Fluid Mechanics