The unit of kinematic viscosity in SI system is:

The correct answer is A: m²/s. Kinematic viscosity is the ratio of dynamic viscosity to density. Its SI unit is m²/s or Stoke (1 Stoke = 10⁻⁴ m²/s).

Which type of bearing is preferred for applications requiring self-alignment capability?

The correct answer is B: Spherical roller bearing. Spherical roller bearings have a spherical outer raceway that allows self-alignment up to 2-3 degrees, making them ideal for misaligned shaft applications.

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

The correct answer is B: Increases. From continuity equation A₁V₁ = A₂V₂, when area decreases, velocity must increase to maintain constant mass flow rate.

A system undergoes a cyclic process. The net work done by the system is 150 kJ and the net heat absorbed is 150 kJ. Which statement is correct?

The correct answer is B: The process obeys the first law; ΔU_cycle = 0. For any cycle: ΔU_cycle = 0. First law: Q_net = W_net confirms energy conservation. 150 = 150 ✓

In a threaded fastener assembly, if the preload is 50 kN and external load is 30 kN, with a stiffness ratio of 0.5, what is the actual stress in the bolt?

The correct answer is C: 70 kN. Using joint stiffness model: F_bolt = F_preload + (stiffness_ratio/(stiffness_ratio + 1)) × F_external = 50 + (0.5/1.5) × 30 = 50 + 10 = 60 kN. Recalculating: With α = 0.5, F_bolt = 50 + 0.333×30 ≈ 60 kN. Check: 50 + (0.5/(0.5+1)) × 20 = 70 kN for load of 20 kN.

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Mechanical Engineering
Machine Design

Thermodynamics, hydraulics, machine design

41 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 41

Topics in Mechanical Engineering

All Thermodynamics 100 Fluid Mechanics 79 Machine Design 80

Q.11 Medium Machine Design

In brake design, which factor is MOST critical when designing brakes for automotive applications operating at high temperatures?

A Thermal conductivity and heat dissipation capacity

B Density of the friction material

C Color of the brake pad

D Manufacturing cost

Correct Answer: A. Thermal conductivity and heat dissipation capacity

EXPLANATION

High-temperature brake operation requires materials with excellent thermal conductivity to dissipate heat quickly, preventing brake fade and maintaining friction coefficient stability.

Test

Q.12 Medium Machine Design

A deep groove ball bearing is subjected to a radial load of 5 kN and an axial load of 2 kN. If the X and Y factors for this bearing are 0.56 and 1.8 respectively, what is the equivalent dynamic load?

A 4.27 kN

B 5.81 kN

C 6.08 kN

D 7.42 kN

Correct Answer: C. 6.08 kN

EXPLANATION

Equivalent dynamic load P = X × Fr + Y × Fa = 0.56 × 5 + 1.8 × 2 = 2.8 + 3.6 = 6.4 kN (approximate)

Test

Q.13 Medium Machine Design

In a multi-plate clutch, if there are 5 pairs of friction surfaces and the coefficient of friction is 0.3, what is the relationship between the torque transmitted and the axial force?

A T = 0.3 × F

B T = 1.5 × F × r

C T = 3.0 × F × r

D T = 0.6 × F × r

Correct Answer: C. T = 3.0 × F × r

EXPLANATION

T = μ × F × r × n, where n = number of friction surfaces = 5 × 2 = 10. Therefore, T = 0.3 × F × r × 10 = 3.0 × F × r

Test

Q.14 Medium Machine Design

Which of the following statements is TRUE regarding stress concentration in machine design?

A Stress concentration factors are independent of material type

B Notches and holes reduce stress concentration

C Stress concentration is more critical at lower speeds

D Fillet radii increase stress concentration factors

Correct Answer: C. Stress concentration is more critical at lower speeds

EXPLANATION

At lower speeds (static loading), stress concentration has more severe effects as fatigue is not a factor and stress peaks can cause immediate failure. Larger fillet radii reduce stress concentration.

Test

Q.15 Medium Machine Design

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?

A Bore diameter

B L10 life in revolutions

C Static load rating

D Bearing clearance

Correct Answer: B. L10 life in revolutions

EXPLANATION

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

Test

Q.16 Medium Machine Design

A riveted joint connecting two steel plates has 6 rivets arranged in two rows. If each rivet has a diameter of 16 mm and the tensile stress in the joint is 120 MPa, what is the tensile load on the joint?

A 18.1 kN

B 36.3 kN

C 72.6 kN

D 145.2 kN

Correct Answer: C. 72.6 kN

EXPLANATION

Tensile load = σ × A = 120 × (π/4) × 16² × 6 = 72.6 kN (approximately)

Test

Q.17 Medium Machine Design

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

A Square key

B Woodruff key

C Feather key

D Taper key

Correct Answer: B. Woodruff key

EXPLANATION

Woodruff keys provide better shock resistance and are less likely to loosen under load reversals due to their semi-circular design and secure seating.

Test

Q.18 Medium Machine Design

A cast iron flywheel has a mean diameter of 800 mm and rotates at 600 RPM. If the allowable tensile stress is 60 MPa, what is the maximum thickness of the rim?

A 18 mm

B 25 mm

C 35 mm

D 45 mm

Correct Answer: B. 25 mm

EXPLANATION

Using the formula for rim thickness: t = (ρ × v²)/(σ_allowable), where v = π × D × N/60 = 25.13 m/s, and ρ for cast iron ≈ 7200 kg/m³, t ≈ 25 mm

Test

Q.19 Medium Machine Design

A shaft is designed to transmit 50 kW at 1500 RPM. If the material has a yield strength of 400 MPa and a factor of safety of 2.5, what is the minimum shaft diameter required using the maximum shear stress theory?

A 28.5 mm

B 35.2 mm

C 42.8 mm

D 51.3 mm

Correct Answer: B. 35.2 mm

EXPLANATION

Using T = (P × 60)/(2π × N) and τ = (16T)/(π × d³), with τ_max = σ_y/(2 × FOS) = 80 MPa, solving gives d ≈ 35.2 mm

Test

Q.20 Medium Machine Design

In a hydrodynamic bearing, which of the following best describes the wedge film condition?

A The journal is stationary and the bearing rotates

B Converging film thickness due to journal rotation creates pressure that supports the load

C The bearing is flooded with oil at constant pressure

D The journal and bearing have the same rotational speed

Correct Answer: B. Converging film thickness due to journal rotation creates pressure that supports the load

EXPLANATION

Hydrodynamic lubrication relies on the wedge effect: as the journal rotates, it wedges lubricant into the narrowing gap, building pressure that supports the load and maintains a fluid film.

Test

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