A simple epicyclic gear train is used in an automobile differential. What is its primary function?
Answer: B
The differential uses an epicyclic gear arrangement to allow the drive wheels to rotate at different speeds during cornering while maintaining equal torque distribution during straight-line acceleration.
Q.22Medium
In a hydrodynamic bearing, which of the following best describes the wedge film condition?
Answer: B
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.
Q.23Medium
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?
Answer: B
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
Q.24Medium
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?
Answer: B
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
Q.25Medium
Which type of key is most suitable for transmitting high torque in rotating shafts with frequent load reversals?
Answer: B
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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Q.26Medium
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 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?
Answer: B
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
Q.28Medium
Which of the following statements is TRUE regarding stress concentration in machine design?
Answer: C
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.
Q.29Medium
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?
Answer: C
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
Q.30Medium
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?
Answer: C
Equivalent dynamic load P = X × Fr + Y × Fa = 0.56 × 5 + 1.8 × 2 = 2.8 + 3.6 = 6.4 kN (approximate)
Q.31Medium
In brake design, which factor is MOST critical when designing brakes for automotive applications operating at high temperatures?
Answer: A
High-temperature brake operation requires materials with excellent thermal conductivity to dissipate heat quickly, preventing brake fade and maintaining friction coefficient stability.
Q.32Medium
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?
Answer: D
Centrifugal tension T_c = m × v² = 0.5 × 20² = 200 N
Q.33Medium
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?
Answer: B
Using P = 2πNT/60 and T = μ × F × r_e, solving gives r_e ≈ 95 mm for the given parameters.
Q.34Medium
A flat belt connects two pulleys with diameters 300 mm and 600 mm. The center distance is 1200 mm. Calculate the belt length approximately.
Answer: C
Using belt length formula: L = 2C + π(D₁+D₂)/2 + (D₂-D₁)²/(4C), the result is approximately 3884 mm.
Q.35Medium
In a helical gear pair with 40° helix angle, what is the axial thrust force if the tangential force is 5000 N?
What is the Lewis form factor for a 20° involute spur gear with 25 teeth?
Answer: B
Using Lewis form factor tables for 20° involute gears, Y ≈ 0.295 for 25 teeth.
Q.37Medium
In a screw-jack with pitch 8 mm and mean diameter 40 mm, if the efficiency is 25%, what is the mechanical advantage?
Answer: C
M.A. = π × d_m / p × (1/efficiency) = (π × 840) × 4 ≈ 47.1.
Q.38Medium
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).
