Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Physics
Lesson Topic: Know that an object in an elliptical orbit travels faster when closer to the Sun and explain this using the conservation of energy
Learning Objective/s:
  • Describe perihelion and aphelion in an elliptical orbit.
  • Explain how conservation of mechanical energy leads to higher orbital speed near the Sun.
  • Calculate the change in orbital speed using given distances.
  • Apply the concept to predict speed variations for other planetary orbits.
Materials Needed:
  • Projector or interactive whiteboard
  • PowerPoint slides with ellipse diagram
  • Calculator or spreadsheet software
  • Worksheet containing the Earth’s orbit data
  • Rulers and compasses for drawing ellipses (optional)
  • Student notebooks
 Introduction:
Begin with a short video showing planets orbiting the Sun, emphasizing that Earth speeds up near perihelion. Ask students what they already know about kinetic and potential energy in orbital motion. State that by the end of the lesson they will be able to explain the speed change using conservation of energy.
Lesson Structure:
  1. Do‑now (5') – Students answer a recall question on kinetic vs. potential energy.
  2. Mini‑lecture (10') – Introduce perihelion, aphelion and the energy equations with slides.
  3. Guided derivation (12') – Work through the energy equality to derive the speed relationship.
  4. Numerical example (8') – Students calculate Earth’s speeds at aphelion and perihelion using the provided table.
  5. Interactive simulation (10') – Explore an online orbit simulator to visualise speed changes.
  6. Check for understanding (5') – Exit ticket: one sentence explaining why speed increases at perihelion.
Conclusion:
Recap that the total mechanical energy remains constant, so a decrease in potential energy near the Sun must be offset by an increase in kinetic energy, causing higher speed. Collect the exit tickets and highlight any misconceptions. Assign homework: students complete a worksheet predicting speed changes for Mars and Venus using the same method.