SSC JE General Engineering (Mechanical) Flashcards

24 sample cards from the General Engineering (Mechanical) deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. Define viscosity and distinguish dynamic from kinematic viscosity.

   Viscosity is a fluid's resistance to shear/flow. Dynamic viscosity (μ, Pa·s) relates shear stress to velocity gradient; kinematic viscosity (ν = μ/ρ, m²/s) is dynamic viscosity per unit density.

2. What distinguishes laminar from turbulent flow, and what is the critical Reynolds number for pipe flow?

   Laminar flow is smooth/layered (Re < 2000); turbulent flow is chaotic with mixing (Re > 4000). The range 2000–4000 is transitional for flow in a pipe.

3. Define the metacentric height and its significance for floating body stability.

   Metacentric height (GM) is the distance between the center of gravity (G) and the metacenter (M). Positive GM (M above G) means stable equilibrium for a floating body.

4. What is the difference between casting and forging as manufacturing processes?

   Casting pours molten metal into a mold to solidify into shape; forging shapes solid metal by compressive force (hammering/pressing), giving a refined grain flow and higher strength.

5. Name the four main types of machining operations performed on a lathe.

   Turning (reducing diameter), facing (machining the end flat), drilling/boring (making/enlarging holes), and threading (cutting screw threads); also taper turning and knurling.

6. What is the difference between up-milling and down-milling?

   Up-milling (conventional): cutter rotates against feed direction, chip thickness increases from zero. Down-milling (climb): cutter rotates with feed, chip thickness decreases; gives better finish but needs backlash-free table.

7. Differentiate between TIG and MIG welding.

   TIG (GTAW) uses a non-consumable tungsten electrode with separate filler and inert gas; MIG (GMAW) uses a consumable wire electrode fed continuously as filler under inert gas shielding. MIG is faster; TIG gives finer control.

8. What are the three main types of production systems?

   Job (or unit) production, batch production, and mass/continuous (flow) production — distinguished by volume, variety, and flow/standardization of products.

9. What is the purpose of an Economic Order Quantity (EOQ) in production planning?

   EOQ = √(2·D·Co / Ch) minimizes total inventory cost by balancing ordering cost (Co) against holding cost (Ch), where D = annual demand.

10. What is the difference between PERT and CPM in project planning?

    PERT is probabilistic, event-oriented, used for uncertain/research projects with three time estimates; CPM is deterministic, activity-oriented, used for well-defined projects with cost-time tradeoffs.

11. Define understeer and oversteer in vehicle dynamics.

    Understeer: vehicle turns less than steering input (front tires lose grip first, it 'pushes' wide). Oversteer: vehicle turns more than input (rear loses grip first, it tends to spin).

12. What is the function of a differential in a vehicle's drivetrain?

    It transmits engine torque to the drive wheels while allowing them to rotate at different speeds during cornering, preventing tire scrub.

13. What is the firing order of a typical inline four-cylinder engine, and why does it matter?

    Commonly 1-3-4-2. The firing order is chosen to balance the engine, minimize vibration, and ensure even power delivery and crankshaft loading.

14. Differentiate between two-stroke and four-stroke engines.

    Four-stroke completes a power cycle in 4 piston strokes (2 crank revolutions) with separate intake/exhaust; two-stroke completes it in 2 strokes (1 revolution) firing every revolution — higher power-to-weight but lower efficiency and more emissions.

15. Name the major types of power plants by energy source.

    Thermal (coal/gas), Hydroelectric, Nuclear, Diesel, Gas turbine, and Renewable (solar, wind, geothermal, tidal, biomass).

16. Define load factor and capacity factor of a power plant.

    Load factor = average load / peak load over a period. Capacity factor = average load / plant rated (installed) capacity. Both indicate how fully capacity is utilized.

17. What is the difference between fixed cost and operating (running) cost of a power plant?

    Fixed (capital) cost is independent of energy generated — interest, depreciation, salaries. Operating cost varies with output — fuel, maintenance, water. Total cost = fixed + running.

18. Describe the four processes of the vapour compression refrigeration cycle.

    1) Compression (vapor compressed, raising P and T), 2) Condensation (heat rejected, vapor to liquid), 3) Expansion (throttling, P and T drop), 4) Evaporation (liquid absorbs heat from space, becomes vapor).

19. Define the Coefficient of Performance (COP) of a refrigerator and a heat pump.

    COP(refrigerator) = desired refrigerating effect / work input = Q2/W. COP(heat pump) = Q1/W = COP(refrigerator) + 1, where Q1 is heat rejected.

20. What is the difference between a refrigerator and a heat pump?

    Both move heat from cold to hot using work input. A refrigerator's useful output is heat removed from the cold space; a heat pump's useful output is heat delivered to the hot space.

21. Define dry-bulb temperature, wet-bulb temperature, and dew point in air conditioning.

    Dry-bulb: actual air temperature. Wet-bulb: temperature read by a thermometer with a wetted wick (reflects evaporative cooling/humidity). Dew point: temperature at which air becomes saturated and moisture condenses.

22. What is relative humidity, and how does it differ from specific humidity?

    Relative humidity = ratio of actual vapor pressure to saturation vapor pressure at the same temperature (%). Specific (absolute) humidity = mass of water vapor per unit mass of dry air (kg/kg).

23. What is the difference between method study and work measurement in work study?

    Method study analyzes and improves the way work is done (eliminating waste, simplifying); work measurement determines the standard time for a qualified worker to do a job (e.g., time study).

24. Differentiate between the X-bar chart and the R chart in statistical quality control, and between Type I and Type II errors.

    X-bar chart monitors process mean (central tendency); R chart monitors process variability (range). Type I error = rejecting a good lot (producer's risk, α); Type II error = accepting a bad lot (consumer's risk, β).

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