Lesson Plan

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Lesson Plan
Grade: Year 12 Date: 17/01/2026
Subject: Physics
Lesson Topic: understand and use the terms elastic deformation, plastic deformation and elastic limit
Learning Objective/s:
  • Define elastic deformation, plastic deformation, and elastic limit.
  • Explain the stress‑strain relationship in the elastic region using Hooke’s law.
  • Identify elastic and plastic behaviour on a stress‑strain diagram.
  • Calculate the extension of a material within its elastic limit (ΔL = FL/AE).
  • Determine whether a given load will cause elastic or plastic deformation for common engineering materials.
Materials Needed:
  • Projector or interactive whiteboard
  • Slide deck with stress‑strain curves
  • Sample rods/wires (steel, aluminium) for demonstration
  • Force sensor or spring scale
  • Worksheets with example problems
  • Calculators (or computer lab)
 Introduction:
Begin with a quick demonstration: stretch a rubber band and ask students what they notice about its return to shape. Recall prior learning on stress, strain and Hooke’s law, linking it to material behaviour. Explain that today they will master the terminology of elastic deformation, plastic deformation and the elastic limit, and will be able to decide whether a load will cause reversible or permanent change.
Lesson Structure:
  1. Do‑now (5’) – Students answer a short question on Hooke’s law on the board.
  2. Mini‑lecture (10’) – Present definitions and stress‑strain curve, highlighting the elastic region and elastic limit.
  3. Interactive simulation (8’) – Use an online applet to stretch virtual rods and observe when deformation becomes permanent.
  4. Hands‑on demo (12’) – Groups use a force sensor on metal wires to measure extension, then compare calculated stress with the material’s elastic limit.
  5. Guided practice (10’) – Worksheet problems where students calculate stress, identify elastic vs. plastic behaviour, and compute ΔL.
  6. Quick check (5’) – Exit ticket: one sentence defining the elastic limit and stating the outcome for a given load.
Conclusion:
Summarise that elastic deformation is reversible, plastic deformation is permanent, and the elastic limit separates the two. Ask students to write one key takeaway on a sticky note as an exit ticket. Assign homework: complete additional stress‑strain problems from the textbook.