Engineering Sciences: Statics, Energy and Fluid Fundamentals
What this section tests
This section probes the shared physics toolkit underlying every branch of engineering: rigid-body statics, Newtonian dynamics, work–energy, conservation of mass and energy, introductory thermodynamics, and fluid statics and continuity. Expect unit-consistent numerical questions rather than long derivations.
Core rules
- SI discipline: convert mm→m, kN→N, kPa→Pa before substituting. A correct number in the wrong unit scores zero.
- Statics: ΣF = 0 and ΣM = 0 about any point. Choose the moment point that eliminates the most unknowns.
- Fluid statics: p = p₀ + ρgh, acting perpendicular to any surface. Pressure depends on depth only, not on container shape or volume.
- Continuity for incompressible flow: A₁v₁ = A₂v₂. Bernoulli holds along a streamline for steady, inviscid, incompressible flow.
- First law for a closed system: Q − W = ΔU, with sign conventions stated explicitly.
- Efficiency = useful output / input, always below 1 for real machines.
Worked example
What is the gauge pressure 5 m below the surface of water (ρ = 1000 kg/m³, g = 9.81 m/s²)? p = ρgh = 1000 × 9.81 × 5 = 49 050 Pa ≈ 49.1 kPa gauge. Absolute pressure adds the atmosphere: 49.1 + 101.3 ≈ 150.4 kPa. If the question says gauge, do not add p_atm.
Traps
Reporting absolute pressure when gauge was asked; using diameter where radius belongs in A = πr²; forgetting a hydraulic jack multiplies force but conserves energy, so the small piston travels farther; treating a static fluid as if pressure varied with volume.