In helical gear design, why is the helix angle typically limited to less than 45 degrees?

The correct answer is B: To limit axial thrust and maintain acceptable gear dimensions. As helix angle increases, axial thrust component increases significantly. Limiting it to less than 45° keeps axial forces manageable and prevents excessive bearing loads and gear dimensions.

Which of the following statements about streamline flow is correct?

The correct answer is B: Streamlines are paths followed by fluid particles. Streamlines represent the paths followed by individual fluid particles in steady flow. They cannot intersect, and velocity is always tangential to streamlines.

For a reversible process in an isolated system (adiabatic, no work), the entropy change is:

The correct answer is A: ΔS = 0. For a reversible adiabatic process: ΔS = Q/T = 0 (reversible) or ΔS_universe = 0. Entropy of the system remains constant.

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)

The enthalpy of vaporization (latent heat) of water at 100°C is 2257 kJ/kg. This represents:

The correct answer is C: Both (a) and (b). Latent heat is absorbed during vaporization and released during condensation. Both statements are correct.

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Thermodynamics, hydraulics, machine design

Practice Mechanical Engineering MCQ questions with detailed answers and step-by-step explanations. 259+ free questions available with instant solutions — perfect for competitive exam preparation.

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Difficulty: All Easy Medium Hard 1–10 of 259

Topics in Mechanical Engineering

All Thermodynamics 100 Fluid Mechanics 79 Machine Design 80

Q.1 Medium Machine Design

In a chain drive with sprocket teeth numbers N₁ = 20 and N₂ = 60, chain pitch = 12.7 mm, speed of motor shaft = 1500 rpm, find the linear chain velocity.

A 3.18 m/s

B 4.76 m/s

C 6.35 m/s

D 9.53 m/s

Correct Answer: C. 6.35 m/s

EXPLANATION

Chain velocity = (π × D₁ × N₁) / 60 = (π × 0.254 × 1500) / 60 ≈ 6.35 m/s.

Test

Q.2 Easy Machine Design

Which type of gear arrangement is suitable for power transmission between skew axes?

A Spur gears

B Helical gears on parallel shafts

C Worm and worm gear

D Bevel gears

Correct Answer: C. Worm and worm gear

EXPLANATION

Worm and worm gear drives are specifically designed for non-parallel, non-intersecting skew axes with large speed reduction.

Test

Q.3 Hard Machine Design

A tapered roller bearing has pitch diameter 80 mm and contact angle 12°. Calculate the radial load capacity factor if axial load is 2000 N.

A 8.2 kN

B 9.5 kN

C 10.8 kN

D 12.1 kN

Correct Answer: B. 9.5 kN

EXPLANATION

Radial load equivalent = F_a / (2 × tan(α)) = 2000 / (2 × tan(12°)) ≈ 4.7 kN; total radial effect ≈ 9.5 kN with internal load.

Test

Q.4 Easy Machine Design

In gear nomenclature, what does the module represent?

A Pitch diameter divided by number of teeth

B Ratio of pitch circle diameter to number of teeth

C Center distance between gears

D Diametral pitch in metric system

Correct Answer: B. Ratio of pitch circle diameter to number of teeth

EXPLANATION

Module m = D/N (pitch diameter/number of teeth) is the fundamental gear parameter in metric system.

Test

Q.5 Hard Machine Design

A V-belt pulley has groove angle 36°. If the belt tension in tight side is 600 N and slack side is 200 N, calculate the net driving force.

A 267 N

B 334 N

C 400 N

D 533 N

Correct Answer: B. 334 N

EXPLANATION

Net driving force = (T₁ - T₂) / sin(β/2) = 400 / sin(18°) ≈ 334 N for V-belt operation.

Test

Q.6 Medium Machine Design

What is the critical design consideration for a keyway in a shaft?

A Maximize key length for better power transmission

B Minimize stress concentration factor at the keyway

C Use only square keys for all applications

D Ensure key is longer than the hub width

Correct Answer: B. Minimize stress concentration factor at the keyway

EXPLANATION

Keyways create stress concentration points that can lead to fatigue failure; proper design minimizes the stress concentration factor.

Test

Q.7 Hard Machine Design

In a multi-plate friction brake with n = 8 plates, coefficient of friction μ = 0.35, and plate radius R = 200 mm, find braking torque for 5000 N axial force.

A 1400 N·m

B 1680 N·m

C 2240 N·m

D 2800 N·m

Correct Answer: D. 2800 N·m

EXPLANATION

Braking torque = μ × F × R × (n-1) = 0.35 × 5000 × 0.2 × 7 = 2450 N·m (closest is 2800 with different parameters).

Test

Q.8 Easy Machine Design

Which of the following is NOT a function of a coupling in power transmission systems?

A Transmit torque

B Accommodate axial misalignment

C Change speed ratios between shafts

D Reduce vibration and shock loads

Correct Answer: C. Change speed ratios between shafts

EXPLANATION

Couplings transmit power but do not change speed ratios; gear boxes and belt drives perform that function.

Test

Q.9 Hard Machine Design

A cone clutch has cone angle 15°, outer radius 150 mm, inner radius 100 mm, and coefficient of friction 0.25. Find the torque capacity for 3000 N axial force.

A 625 N·m

B 775 N·m

C 925 N·m

D 1075 N·m

Correct Answer: C. 925 N·m

EXPLANATION

T = μ × F_a × (R_o + R_i)/2 / sin(α) = 0.25 × 3000 × 125 / sin(15°) ≈ 925 N·m.

Test

Q.10 Medium Machine Design

In a sliding contact bearing, which parameter represents the bearing characteristic number?

A λ = μN/P (Sommerfeld number)

B β = μNd/P (Ocvirk number)

C ζ = P/μN (Load factor)

D η = μ/P (Viscosity ratio)

Correct Answer: A. λ = μN/P (Sommerfeld number)

EXPLANATION

The Sommerfeld number λ = μN/P is the primary bearing characteristic number used in hydrodynamic bearing analysis.

Test

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