Lesson Plan

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Lesson Plan
Grade: Date: 17/01/2026
Subject: Physics
Lesson Topic: understand that the area under the force–extension graph represents the work done
Learning Objective/s:
  • Describe elastic and plastic deformation and identify the elastic limit on a force‑extension graph.
  • Explain why the area under a force‑extension curve represents the work done on a material.
  • Calculate work done in elastic (triangular) and plastic (rectangular/trapezoidal) regions using geometry or integration.
  • Apply the method to solve numerical problems involving spring constants and constant‑force plastic regions.
  • Interpret graph features such as yield point and ultimate tensile strength in terms of energy absorption.
Materials Needed:
  • Projector or interactive whiteboard
  • Graph paper and rulers
  • Spring or rubber band for a quick demo
  • Worksheet with force‑extension graphs and practice problems
  • Calculator (or spreadsheet) for area calculations
  • Whiteboard markers
 Introduction:
Begin with a quick demonstration stretching a rubber band to show how force increases with extension. Ask students to recall Hooke’s law and what happens when the material reaches its elastic limit. Explain that today they will link the graph’s shaded area to the physical concept of work. Success will be measured by correctly calculating work from given graphs.
Lesson Structure:
  1. Do‑Now (5'): Students sketch a simple force‑extension line for a spring and label the elastic region.
  2. Mini‑lecture (10'): Review elastic vs. plastic behaviour and introduce the area‑under‑curve concept using the projector.
  3. Guided practice (12'): Work through the steel‑wire example, calculating triangular and rectangular areas together.
  4. Collaborative activity (15'): In pairs, students plot a custom force‑extension graph on graph paper and compute total work, checking with calculators.
  5. Check for understanding (5'): Quick exit‑ticket quiz with one problem on identifying work from a given graph.
  6. Wrap‑up (3'): Summarise key points and assign homework.
Conclusion:
Recap that work equals the area under the force‑extension curve, differing in shape for elastic and plastic regions. Students complete an exit ticket summarising the steps to calculate work. For homework, assign two practice problems from the worksheet to reinforce the calculations.