Technological World: engineering design, technical drawing, and materials
This domain tests the design process, reading and producing technical drawings, and choosing materials from their properties. Questions may ask you to identify constraints, interpret a scale, recognize line types, or justify a material choice.
Engineering design
The design process starts with a need and specifications. Constraints are limits such as cost, safety, size, or available materials; criteria are the goals the solution should meet. Designers brainstorm, select a solution, build a prototype, test it, and iterate. A prototype is a model used for testing, not automatically the final product. Good evaluation compares test results with the original criteria and constraints.
Technical drawing
Orthographic projection shows separate front, top, and side views; isometric drawings show three dimensions in one view. Visible edges are solid lines, hidden edges are dashed lines, and centre lines are long-short dashed. Dimensions show true sizes, while a scale compares drawing length to real length. A scale of 1:20 means 1 unit on the drawing represents 20 units in reality. Tolerances state acceptable variation in a dimension.
Materials
Materials are selected for mechanical properties (strength, hardness, elasticity, toughness), physical properties (density, thermal and electrical conductivity, melting point), and chemical properties (corrosion resistance, reactivity). A material that is strong but brittle may fail suddenly; a tough material absorbs impact. Cost, availability, mass, and recyclability are also design constraints.
Worked example
A drawing uses scale 1:20. A measured length on the drawing is 60 mm. Actual length = 60 mm × 20 = 1200 mm = 1.20 m. If the real object must be 1.50 m, the drawing length should be 1500 mm ÷ 20 = 75 mm. The reasoning shows that scale is a multiplier, and units must be converted consistently before comparing.
Traps
- Confusing criteria with constraints.
- Treating a prototype as proof that no testing is needed.
- Using dashed lines for visible edges.
- Inverting a scale such as 1:20.
- Choosing a material by appearance while ignoring strength, mass, or corrosion.
- Forgetting that dimensions on a scaled drawing are not the real dimensions unless converted.