| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: Describe an experiment to determine the position of the centre of gravity of an irregularly shaped plane lamina |
Learning Objective/s:
- Describe the experimental method for locating the centre of gravity of an irregular lamina.
- Explain why the balance line passes through the centre of gravity.
- Apply the procedure to determine the coordinates of the centre of gravity and record data accurately.
- Evaluate sources of experimental error and suggest improvements.
|
Materials Needed:
- Irregular thin lamina (cardboard cut‑out)
- Two thin straight supports (metal rods or wooden strips)
- Adjustable mounting board or bench
- Plumb line with a small weight
- Ruler or measuring scale
- Paper and pencil for recording
- Calculator (optional for coordinate calculations)
|
Introduction:
Begin with a quick demonstration of a simple symmetrical shape balancing on a fingertip to spark curiosity about hidden balance points.
Recall that the centre of gravity is the point where the weight acts and that for uniform objects it coincides with the centre of mass.
Today students will design and carry out an experiment to locate the centre of gravity of an irregular lamina and will be able to explain the underlying principle.
|
Lesson Structure:
- Do‑now (5'): Students answer a short question on the centre of gravity of a rectangle (check understanding).
- Mini‑lecture (10'): Review the principle that a body balances when supported through its centre of gravity; introduce the balance‑line method (concept questions).
- Demonstration (5'): Teacher sets up the lamina on two supports and shows how the line through the supports aligns with the CG.
- Guided practice (15'): Pairs set up the apparatus, locate the first balance line L₁, mark contact points and record data (teacher circulates).
- Repetition (10'): Students rotate the lamina, obtain a second line L₂, extend both lines to find intersection G and measure its coordinates (peer check).
- Data analysis & error discussion (10'): Groups compare results, discuss sources of error and how to minimise them; complete an exit ticket.
|
Conclusion:
Summarise that the intersection of two balance lines gives the centre of gravity and that the method relies on the lamina being in static equilibrium.
For the exit ticket, each student writes the coordinates of G and one possible source of error.
H homework: complete a worksheet applying the balance‑line technique to a new irregular shape.
|