Lesson Plan

Resources → Subject Notes → Physics → Notes
Lesson Plan
Grade: Date: 25/02/2026
Subject: Physics
Lesson Topic: calculate the upthrust acting on an object in a fluid using the equation F = ρgV (Archimedes’ principle)
Learning Objective/s:
  • Describe Archimedes’ principle and the concept of upthrust.
  • Derive the buoyant force formula F = ρ g V from pressure differences.
  • Apply the formula to calculate upthrust for fully and partially submerged objects.
  • Analyse common errors such as using incorrect volume or density.
  • Evaluate real‑world examples (e.g., submarines, floating blocks) using the principle.
Materials Needed:
  • Projector or interactive whiteboard
  • Printed worksheet with practice problems
  • Calculator (or scientific calculator app)
  • Density tables for common fluids
  • Demonstration kit: water tank, cubes, measuring cylinder
  • Rulers or measuring tape
 Introduction:
Begin with a quick demonstration: drop a solid cube into a clear water tank and ask students what they observe. Recall prior learning about pressure variation with depth and the concept of equilibrium. Explain that today they will use Archimedes’ principle to quantify the upward force, and the success criteria will be correctly calculating upthrust and predicting whether objects float.
Lesson Structure:
  1. Do‑now (5') – Students answer a short prompt on fluid pressure on the board.
  2. Mini‑lecture (10') – Review pressure, density, and derive F = ρ g V using the element approach.
  3. Guided example (10') – Walk through the cube problem, completing a calculation table together.
  4. Hands‑on activity (15') – In small groups, measure the volume of irregular objects, use density tables to compute upthrust, and record results.
  5. Concept check (5') – Quick Kahoot quiz on common mistakes.
  6. Extension discussion (5') – Explain how submarines control buoyancy using the formula.
Conclusion:
Summarise that upthrust equals the weight of displaced fluid and that accurate volume and density are essential. Students complete an exit ticket stating the upthrust for a given sphere in oil. Assign homework: three additional problems from the textbook, including a partially submerged block. Remind them to bring their density tables for the next lesson.