| Lesson Plan |
| Grade: Year 12 |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: understand that the upthrust acting on an object in a fluid is due to a difference in hydrostatic pressure |
Learning Objective/s:
- Describe how hydrostatic pressure varies with depth and how this creates a pressure difference on a submerged object.
- Explain why the resultant upthrust equals the weight of the displaced fluid (Archimedes’ principle).
- Apply the pressure‑difference method to predict whether an object will float, sink, or remain neutrally buoyant.
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Materials Needed:
- Projector and screen
- Digital slide showing pressure‑depth diagram
- Worksheet with sample calculations and misconception check
- Clear water tank with a small rectangular block (for demo)
- Balance scales for measuring mass of objects
- Ruler and measuring tape
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Introduction:
Begin with a quick video of a boat gliding on water to spark curiosity about why it stays afloat. Ask students what forces they think act on the boat and link this to prior knowledge of weight and pressure. State that by the end of the lesson they will be able to articulate the pressure‑difference explanation for buoyancy and check their understanding against common misconceptions.
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Lesson Structure:
- Do‑now (5 min): Students answer a short question on pressure variation with depth on the board.
- Mini‑lecture (10 min): Present the formula p = ρgh and derive the pressure difference on top and bottom of a submerged block.
- Guided practice (12 min): Work through the step‑by‑step derivation of upthrust on the projected slide, prompting students to fill in missing algebra.
- Hands‑on demonstration (8 min): Submerge the block in the water tank, measure forces with a spring scale, and compare with calculated F_B.
- Concept‑check (5 min): Quick quiz using clickers on floating vs. sinking conditions.
- Misconception discussion (5 min): Present common errors and have pairs correct them.
- Worksheet completion (10 min): Students solve a problem on determining buoyancy for a given object.
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Conclusion:
Summarise that upthrust originates from the hydrostatic pressure gradient and always equals the weight of displaced fluid. Ask each student to write one key takeaway on a sticky note as an exit ticket. For homework, assign a set of problems requiring calculation of buoyant force for irregular shapes.
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