General Engineering (Common Fundamentals)
What is tested
General Engineering is shared by Civil and Mechanical candidates, so it stays at first-year fundamentals: units and measurement, force and moment, work-power-energy, simple machines, stress and strain, material properties, basic thermal and fluid ideas, and workshop or drawing basics.
Core rules
- SI: force in newton, stress and pressure in pascal; 1 N/mm² = 1 MPa = 10⁶ Pa.
- Moment = force × perpendicular distance; a couple has moment F × d and no resultant force.
- Mechanical advantage = load/effort; velocity ratio = effort distance/load distance; efficiency = MA/VR.
- Hooke's law: stress is proportional to strain within the elastic limit; E = stress/strain; Poisson's ratio = lateral strain/longitudinal strain, about 0.3 for steel.
- Direct stress σ = P/A; elongation δ = PL/AE.
- Vernier least count = 1 MSD − 1 VSD (0.02 mm for a 50-division vernier); micrometer least count = pitch/number of divisions, usually 0.01 mm.
- Gauge pressure = absolute pressure − atmospheric pressure.
Worked example
A 20 mm diameter bar carries 31.4 kN. Area = πd²/4 = 314.16 mm². Stress = 31,400/314.16 ≈ 100 N/mm² = 100 MPa. With E = 2×10⁵ MPa and length 1 m, elongation = PL/AE = (31,400 × 1000)/(314.16 × 2×10⁵) ≈ 0.5 mm.
Traps
Reporting stress in N rather than N/mm²; forgetting to halve the diameter before squaring; mixing gauge and absolute pressure; using velocity ratio where efficiency is asked; applying Hooke's law beyond the proportional limit.