Engineering
In the Engineering domain of this GATE XH guide, questions test whether you can convert a physical situation into a free-body or control-volume model, apply conservation laws, and check the result for dimensional and limiting-case consistency. The emphasis is on correct setup, not memorised numbers.
Core rules and concepts
- Draw the free-body diagram before writing equations; show every external force and support reaction.
- For static equilibrium use ΣF = 0 and ΣM = 0 about a convenient point.
- For steady-flow energy balances, account for enthalpy, kinetic energy, potential energy, heat, and work with a consistent sign convention.
- Axial stress is σ = F/A; engineering strain is ε = ΔL/L; within the elastic limit E = σ/ε.
- Keep units consistent: convert kN to N, mm to m, and check that both sides of every equation have the same dimensions.
Worked example
A simply supported beam of span 4 m carries a central point load of 10 kN. Ignore self-weight. By symmetry, each vertical reaction is 5 kN. The bending moment at midspan is R × L/2 = 5 kN × 2 m = 10 kN·m; equivalently WL/4 = 10 × 4/4 = 10 kN·m. The shear force changes sign at midspan, so the maximum moment occurs there for this loading.
Traps that cost marks
Mixing kN and N, using diameter as radius when computing area, forgetting self-weight, and applying equilibrium to only part of a system are common. A sign error in a moment equation can reverse a reaction. Always state the assumed direction and check a limiting case, such as zero load or zero span.