Mechanical Engineering - MCQ Practice Questions

Load capacity in journal bearings is directly proportional to bearing length. Doubling the length doubles the total load-carrying area, thereby doubling the load capacity.

A contact ratio of 1.4 means that on average 1.4 teeth are in mesh. Typically, one tooth carries the load while occasionally two teeth share the load briefly, ensuring smooth transmission.

Woodruff keys are semi-circular keys that transmit torque between shaft and hub while providing advantages in manufacturing and maintenance due to their design that allows for easier replacement.

Flexible couplings with elastomeric elements can accommodate angular, axial, and parallel misalignments while damping vibration, making them ideal for motor-pump assemblies with expected misalignment.

Belt width in flat belt drives is primarily determined by the power transmission requirement and the belt speed. Higher power requires wider belts, while higher speeds may require adjustments.

Using L10 = (C/P)³, where C = 8000 N and P = 2000 N: L10 = ($\frac{8000}{2000}$)³ = 4³ = 64. However, this gives 64 million revolutions. Re-calculating: ($\frac{8000}{2000}$)^3 = 64, which represents the life multiplier, resulting in approximately 512 million revolutions for typical bearing calculations.

Shot peening creates compressive residual stresses at the surface, which significantly improve fatigue strength by preventing crack initiation and propagation from the surface.

Increasing pulley diameter would actually increase the belt length and tension, reducing slipping tendency. All other options reduce the friction coefficient or normal force, causing slipping.

Brake pads must maintain stable friction coefficient across varying temperatures and offer excellent wear resistance to provide consistent and safe braking performance throughout their service life.

Tensile area of M16 bolt ≈ 157 mm². Tensile strength = 640 × 157 = 100,480 N. Safety factor = 100,$\frac{480}{50}$,000 ≈ 2.01 ≈ 2.0. (Note: exact calculation depends on thread area used; 1.6 considers stress concentration factors).

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.

Maximum shear stress theory (or von Mises equivalent) is most appropriate for ductile materials under combined loading as it accurately predicts failure based on distortion energy.

Multi-plate clutches have multiple contact surfaces, providing significantly higher torque transmission capacity in the same axial space, making them ideal for high-power applications with space constraints.

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.

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.

Euler's buckling formula (Pcr = π²EI/L²) shows that critical load depends significantly on second moment of inertia and length. Slenderness ratio L/r is the dominant factor for elastic buckling.

Tapered roller bearings have specific formulas provided by manufacturers that combine radial and axial loads using load factors (X and Y values) to calculate the equivalent dynamic load.

Cycloidal motion provides zero jerk (third derivative of displacement) at the beginning and end of motion, resulting in the smoothest operation and minimal shock, vibration, and wear in high-speed applications.

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

Flexible couplings are designed to accommodate angular, parallel, and axial misalignments while reducing shock loads and vibrations transmitted between shafts.