| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: determine the elastic potential energy of a material deformed within its limit of proportionality from the area under the force–extension graph |
Learning Objective/s:
- Describe elastic vs. plastic deformation and the limit of proportionality.
- Apply Hooke’s law to determine the spring constant from force‑extension data.
- Calculate elastic potential energy by finding the area under the linear portion of a force‑extension graph.
- Analyse worked examples and solve similar problems using both the triangle‑area and k‑formula methods.
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Materials Needed:
- Projector or interactive whiteboard
- Graph paper and rulers
- Spring or rubber‑band samples
- Digital scale / force sensor (optional)
- Worksheets with force‑extension graphs
- Calculator
- Whiteboard markers
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Introduction:
Begin with a quick demonstration stretching a rubber band attached to a force sensor, asking students what they notice about the force‑extension relationship.
Recall Hooke’s law and the concept of the limit of proportionality from previous lessons.
Explain that today they will learn how to extract the stored elastic energy from the area under the linear part of the graph, which they will demonstrate through calculations and a brief lab activity.
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Lesson Structure:
- Do‑Now (5'): Students sketch a force‑extension graph for a spring given F = kx and label the linear region. (Check understanding.)
- Mini‑lecture (10'): Review elastic vs. plastic deformation, limit of proportionality, and the formulas Uₑ = ½Fₘₐₓ xₘₐₓ = ½k xₘₐₓ². (Use projector.)
- Guided example (12'): Work through the steel‑wire example, calculating Uₑ by both methods while students complete the worksheet steps.
- Hands‑on activity (15'): In small groups, use spring kits or rubber bands with force sensors to record data, plot the graph, identify Fₘₐₓ and xₘₐₓ, and compute elastic potential energy.
- Concept check (8'): Quick quiz (Kahoot/exit ticket) with three questions on identifying the correct area and common misconceptions.
- Summary discussion (5'): Review key steps and address misconceptions.
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Conclusion:
Summarise that elastic potential energy is obtained from the triangular area under the linear portion of the force‑extension graph and that the spring constant remains constant only within this region.
Ask students to write a one‑sentence exit ticket stating the condition for using the area‑under‑curve method.
For homework, assign two practice problems from the worksheet to reinforce the calculations.
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