Lesson Plan

• Define load, extension, compression and the limit of proportionality.
• Distinguish between tensile and compressive loading situations.
• Apply Hooke’s law to calculate stress, strain and extension within the elastic region.
• Interpret a stress‑strain graph and locate the limit of proportionality.

• Projector and screen
• Whiteboard and markers
• Spring scale (or force sensor)
• Metal/wooden rods for demonstration
• Rulers or digital calipers
• Student worksheets with calculation and graph tasks
• Calculators

Begin with the question, “Why don’t bridges collapse when heavy trucks drive over them?” Connect this to students’ prior knowledge of force and ask them to predict what happens to a material under a load. Explain that today they will learn the precise language—load, extension, compression, and limit of proportionality—used to describe those behaviours and how to check their understanding through a simple success criterion.

1. Do‑now (5 min): Quick written quiz on the difference between force and stress.
2. Mini‑lecture (10 min): Introduce definitions of load, extension, compression and limit of proportionality with real‑world examples.
3. Demonstration (10 min): Use a spring scale and a rod to show how increasing load produces measurable extension; record data.
4. Guided practice (12 min): In pairs, calculate stress, strain and extension for the given steel‑rod example using Hooke’s law.
5. Graphing activity (8 min): Students plot stress vs. strain points, identify the linear region and mark the limit of proportionality.
6. Check for understanding (5 min): Exit‑ticket question – “What indicates the limit of proportionality on a stress‑strain graph?”

Summarise that load produces extension or compression, that stress and strain are related linearly only up to the limit of proportionality, and that this point can be read from a graph. Collect exit tickets and assign a worksheet with additional Hooke’s‑law problems for homework.