Lesson Plan

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Lesson Plan
Grade: Date: 17/01/2026
Subject: Physics
Lesson Topic: State what is meant by centre of gravity
Learning Objective/s:
  • Define centre of gravity and differentiate it from centre of mass.
  • Explain how the centre of gravity influences balance and stability in a uniform gravitational field.
  • Locate the centre of gravity for simple shapes using symmetry and for irregular objects using balancing or moments.
  • Apply the centre‑of‑gravity formula to calculate its position for a system of discrete masses.
  • Identify common misconceptions about centre of gravity.
Materials Needed:
  • Projector and screen
  • Whiteboard and markers
  • Ruler and measuring tape
  • Uniform rods, rectangular plates, and solid sphere models
  • Balance scale (pivot point)
  • Worksheet with calculation tasks
  • Calculators
 Introduction:
Begin with a quick demonstration of a ruler balanced on a finger to spark curiosity about why it stays level. Ask students what they think determines the point of balance and link this to prior knowledge of torque. State that by the end of the lesson they will be able to define centre of gravity, locate it for various objects, and recognise its role in stability.
Lesson Structure:
  1. Do‑now (5'): Students write a definition of “centre of gravity” on a sticky note and display it.
  2. Mini‑lecture (10'): Teacher presents the formal definition, relationship to centre of mass, and key points using projector.
  3. Demonstration (10'): Balance a uniform rod on a pivot; discuss equal torques and identify the CG.
  4. Guided practice (12'): In pairs, students use the formula to calculate CG for given discrete‑mass systems and then verify with the balance scale.
  5. Misconception check (5'): Quick Kahoot quiz addressing common errors (e.g., CG must be inside the object).
  6. Application activity (8'): Students sketch the CG for an irregular shape and explain how it affects stability in real‑world contexts.
  7. Exit ticket (5'): Write one example where knowing the CG is crucial (e.g., designing a bridge, sports equipment).
Conclusion:
Recap the definition, the methods for locating the centre of gravity, and why it matters for balance and design. Collect exit tickets to gauge understanding and assign a short homework: calculate the CG of a household object using the provided worksheet.