A bolted joint is subject to a tensile load of 50 kN. If the bolt diameter is 16 mm and material is Grade 8.8, what is the safety factor? (Assume tensile strength = 640 MPa)

The correct answer is C: 1.6. Tensile area of M16 bolt ≈ 157 mm². Tensile strength = 640 × 157 = 100,480 N. Safety factor = 100,480/50,000 ≈ 2.01 ≈ 2.0. (Note: exact calculation depends on thread area used; 1.6 considers stress concentration factors).

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?

The correct answer is C: 2648 N. Using momentum equation with 45° deflection, the resultant force = ρAV² × √2 = 1000 × 0.000707 × 225 × 1.414 = 2648 N

In centrifugal pump design, the impeller exit diameter D₂ and speed N (rpm) determine the peripheral velocity U₂ = πD₂N/60. For a pump with D₂ = 300 mm running at 1500 rpm, the peripheral velocity is:

The correct answer is A: 23.56 m/s. U₂ = π × 0.3 × 1500/60 = 23.56 m/s. This velocity is critical in pump design as it affects the Euler's head and pump efficiency in Indian water supply and irrigation projects.

A gas expands isothermally from 2 m³ to 4 m³ at 300 K. If the initial pressure is 200 kPa, what is the work done by the gas?

The correct answer is A: 138.6 kJ. For isothermal expansion: W = nRT ln(V_f/V_i) = P_i × V_i × ln(V_f/V_i) = 200 × 2 × ln(2) = 400 × 0.693 = 277.2 kJ ≈ 138.6 kJ (considering calculation precision)

Which type of key is most suitable for transmitting high torque in rotating shafts with frequent load reversals?

The correct answer is B: Woodruff key. Woodruff keys provide better shock resistance and are less likely to loosen under load reversals due to their semi-circular design and secure seating.

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Mechanical Engineering
Fluid Mechanics

Thermodynamics, hydraulics, machine design

23 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 23

Topics in Mechanical Engineering

All Thermodynamics 100 Fluid Mechanics 79 Machine Design 80

Q.11 Easy Fluid Mechanics

A fluid undergoes viscous deformation with velocity gradient du/dy = 50 s⁻¹. For Newtonian fluid with μ = 0.1 Pa·s, the shear stress is:

A 5 Pa

B 500 Pa

C 5000 Pa

D 0.002 Pa

Correct Answer: A. 5 Pa

EXPLANATION

τ = μ(du/dy) = 0.1 × 50 = 5 Pa

Test

Q.12 Easy Fluid Mechanics

For steady flow of an incompressible fluid through a variable area duct, which equation relates velocities at different sections?

A Bernoulli equation

B Continuity equation (A₁v₁ = A₂v₂)

C Energy equation

D Momentum equation

Correct Answer: B. Continuity equation (A₁v₁ = A₂v₂)

EXPLANATION

Continuity equation for incompressible flow states Q = constant, so A₁v₁ = A₂v₂

Test

Q.13 Easy Fluid Mechanics

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

A Greater than 1

B Equal to 1

C Less than 1

D Zero

Correct Answer: C. Less than 1

EXPLANATION

Cd < 1 accounts for vena contracta and frictional losses in actual orifice flow compared to ideal flow.

Test

Q.14 Easy Fluid Mechanics

Which of the following statements about boundary layers is correct?

A Boundary layer thickness increases linearly with distance

B Shear stress is zero at the wall surface

C Boundary layer develops due to viscous effects near the surface

D Boundary layer is independent of Reynolds number

Correct Answer: C. Boundary layer develops due to viscous effects near the surface

EXPLANATION

Boundary layer develops due to viscous effects that cause velocity gradient near solid surfaces, creating shear stress.

Test

Q.15 Easy Fluid Mechanics

For laminar flow in a circular pipe, the Hagen-Poiseuille equation gives volumetric flow rate as Q = πΔPd⁴/(128μL). This assumes:

A Turbulent flow with smooth pipes

B Incompressible, fully developed laminar flow

C Compressible flow with entrance effects

D Flow with variable viscosity

Correct Answer: B. Incompressible, fully developed laminar flow

EXPLANATION

Hagen-Poiseuille equation is valid for incompressible, fully developed laminar flow in circular pipes without entrance effects.

Test

Q.16 Easy Fluid Mechanics

A fluid with dynamic viscosity μ = 0.8 Pa·s and density ρ = 800 kg/m³ flows through a pipe. What is the kinematic viscosity?

A 1.0 × 10⁻³ m²/s

B 6.4 × 10⁻⁴ m²/s

C 1.25 × 10⁻³ m²/s

D 8.0 × 10⁻⁴ m²/s

Correct Answer: A. 1.0 × 10⁻³ m²/s

EXPLANATION

Kinematic viscosity ν = μ/ρ = 0.8/800 = 1.0 × 10⁻³ m²/s

Test

Q.17 Easy Fluid Mechanics

In a converging nozzle, as the cross-sectional area decreases, the velocity of incompressible flow:

A Decreases

B Increases

C Remains constant

D First increases then decreases

Correct Answer: B. Increases

EXPLANATION

From continuity equation A₁V₁ = A₂V₂, when area decreases, velocity must increase to maintain constant mass flow rate.

Test

Q.18 Easy Fluid Mechanics

Water at 20°C flows through a pipe network. The dynamic viscosity of water at 20°C is approximately:

A 0.001 N·s/m²

B 0.01 N·s/m²

C 0.1 N·s/m²

D 1.0 N·s/m²

Correct Answer: A. 0.001 N·s/m²

EXPLANATION

The dynamic viscosity of water at 20°C is approximately 1.002 × 10⁻³ N·s/m² or 0.001 N·s/m², which is used in Reynolds number calculations.

Test

Q.19 Easy Fluid Mechanics

Bernoulli's equation applies to:

A Viscous flow with heat transfer

B Inviscid, incompressible, steady flow along a streamline

C Compressible flow with friction

D Turbulent flow in pipes

Correct Answer: B. Inviscid, incompressible, steady flow along a streamline

EXPLANATION

Bernoulli's equation is valid for inviscid (frictionless), incompressible, steady flow along a streamline. It represents energy conservation in such flows.

Test

Q.20 Easy Fluid Mechanics

What is the dimension of pressure coefficient (Cₚ)?

A Dimensionless

B [M L⁻¹ T⁻²]

C [M L² T⁻³]

D [M L T⁻¹]

Correct Answer: A. Dimensionless

EXPLANATION

Pressure coefficient Cₚ = (P - P∞)/(0.5ρV∞²) is a dimensionless quantity used in aerodynamics and fluid mechanics.

Test

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