Basic Engineering Aptitude and Applied Technical Reasoning
This domain checks whether a candidate can reason like an engineer without relying on a single branch's long derivations. It tests SI units, dimensional consistency, simple machines, work-power-energy, electrical energy billing, estimation, graph reading, material properties, and basic safety factors. Questions are usually short numericals or assertion-style judgements about whether a stated result is physically plausible.
Core rules
- Every equation must be dimensionally homogeneous; add or equate only quantities with the same dimensions.
- Mechanical power = force × velocity; electrical power = voltage × current; energy = power × time.
- Efficiency = useful output ÷ input, always less than 100% for a real machine.
- Mechanical advantage = load ÷ effort; velocity ratio = effort distance ÷ load distance.
- For a pump or turbine, hydraulic power is ρgQH, with Q in m³/s and H in metres.
Worked example
A pump draws 2 kW and raises 600 L/min through a 15 m head. Convert flow: 600 L/min = 0.01 m³/s. Hydraulic power = 1000 × 9.81 × 0.01 × 15 = 1471.5 W ≈ 1.47 kW. Pump efficiency = 1.47/2 = 0.735, i.e. about 73.5%. The reasoning shows why the flow must be converted before using ρgQH.
Traps that cost marks
Treating kW and kWh as interchangeable; using gauge pressure where absolute pressure is required; forgetting that density of water is 1000 kg/m³, not 1; using diameter in place of radius in area calculations; accepting an efficiency above 100% without checking the input definition.
Key points
- Convert litres, minutes, and centimetres before substitution.
- kWh is energy; kW is power.
- Real-machine efficiency cannot exceed 100%.
- Dimensional checks quickly eliminate wrong options.
- Estimate the order of magnitude before exact calculation.