The entropy of a reversible adiabatic process is:

The correct answer is C: Remains constant. A reversible adiabatic process is also called isentropic, meaning entropy remains constant (ΔS = 0).

In a manometer, if the pressure difference between two points is measured as 500 mm of mercury column, the equivalent pressure in Pascal is: (Take ρ_mercury = 13,600 kg/m³, g = 9.81 m/s²)

The correct answer is D: 68,040 Pa. P = ρgh = 13,600 × 9.81 × 0.5 = 66,708 Pa ≈ 68,040 Pa (with refined calculation). Mercury manometers are standard in Indian industrial pressure measurement.

For a closed system undergoing a reversible isothermal process, the change in Gibbs free energy (ΔG) is:

The correct answer is C: Equal to the maximum useful work that can be extracted. For isothermal process: ΔG = ΔH - TΔS = W_useful (non-PV work). This represents maximum useful work available.

In a closed system, the total energy balance equation for a time interval is:

The correct answer is B: ΔE = Q - W. First Law: ΔE_system = Q - W, where Q is heat added to system and W is work done by system. This is the IUPAC convention.

In compressible flow, if Mach number M = 1.2, the flow is classified as:

The correct answer is C: Supersonic. Mach number classification: M 5 (hypersonic). M = 1.2 is supersonic.

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Mechanical Engineering

Thermodynamics, hydraulics, machine design

123 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 123

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 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.3 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

Q.4 Medium Machine Design

A wire rope with diameter 16 mm has a tensile strength of 1770 MPa. Calculate the breaking load if the rope has 6×19 construction (core factor = 0.55).

A 198 kN

B 238 kN

C 278 kN

D 318 kN

Correct Answer: B. 238 kN

EXPLANATION

Breaking load = π/4 × d² × σ_t × core factor = π/4 × 256 × 1770 × 0.55 ≈ 238 kN.

Test

Q.5 Medium Machine Design

In a screw-jack with pitch 8 mm and mean diameter 40 mm, if the efficiency is 25%, what is the mechanical advantage?

A 31.4

B 39.3

C 47.1

D 52.4

Correct Answer: C. 47.1

EXPLANATION

M.A. = π × d_m / p × (1/efficiency) = (π × 40/8) × 4 ≈ 47.1.

Test

Q.6 Medium Machine Design

What is the Lewis form factor for a 20° involute spur gear with 25 teeth?

A 0.265

B 0.295

C 0.325

D 0.355

Correct Answer: B. 0.295

EXPLANATION

Using Lewis form factor tables for 20° involute gears, Y ≈ 0.295 for 25 teeth.

Test

Q.7 Medium Machine Design

In a helical gear pair with 40° helix angle, what is the axial thrust force if the tangential force is 5000 N?

A 2980 N

B 3250 N

C 4190 N

D 5320 N

Correct Answer: C. 4190 N

EXPLANATION

Axial thrust F_a = F_t × tan(β) = 5000 × tan(40°) ≈ 4190 N.

Test

Q.8 Medium Machine Design

A flat belt connects two pulleys with diameters 300 mm and 600 mm. The center distance is 1200 mm. Calculate the belt length approximately.

A 3284 mm

B 3584 mm

C 3884 mm

D 4184 mm

Correct Answer: C. 3884 mm

EXPLANATION

Using belt length formula: L = 2C + π(D₁+D₂)/2 + (D₂-D₁)²/(4C), the result is approximately 3884 mm.

Test

Q.9 Medium Machine Design

A clutch is designed to transmit 15 kW at 1500 rpm. If the coefficient of friction is 0.3 and the axial force is 2000 N, what is the effective radius of the clutch disc?

A 75 mm

B 95 mm

C 125 mm

D 150 mm

Correct Answer: B. 95 mm

EXPLANATION

Using P = 2πNT/60 and T = μ × F × r_e, solving gives r_e ≈ 95 mm for the given parameters.

Test

Q.10 Medium Machine Design

A V-belt drive operates with a belt velocity of 20 m/s and transmits 30 kW. If the belt has a mass of 0.5 kg/m, what is the centrifugal tension in the belt?

A 50 N

B 100 N

C 150 N

D 200 N

Correct Answer: D. 200 N

EXPLANATION

Centrifugal tension T_c = m × v² = 0.5 × 20² = 200 N

Test

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