| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: understand that a force of constant magnitude that is always perpendicular to the direction of motion causes centripetal acceleration |
Learning Objective/s:
- Describe the relationship between uniform circular motion, centripetal force and centripetal acceleration.
- Derive and apply the formula \(a_c = v^{2}/r\) (or \(a_c = \omega^{2}r\)) to solve numerical problems.
- Explain why a constant‑magnitude force perpendicular to velocity does not change the speed of the object.
- Analyse real‑world examples (e.g., string tension, banked curves, planetary orbits) to identify the source of centripetal force.
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Materials Needed:
- Projector or interactive whiteboard
- PowerPoint/Google Slides with diagrams and derivation steps
- Worksheet with derivation, worked example, and conceptual questions
- String, small mass, and stopwatch for a quick tabletop demo
- Exit‑ticket slips or online quiz link
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Introduction:
Begin with a short video of a roller‑coaster loop to capture interest, then ask students how the cars stay on the track without speeding up. Review the definition of acceleration and the idea that forces change motion. State that by the end of the lesson they will be able to predict the required force for any object moving in a circle at constant speed.
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Lesson Structure:
- Do‑Now (5'): Quick sketch of an object in circular motion; label velocity and guess direction of the net force.
- Conceptual input (10'): Teacher explains uniform circular motion, shows the velocity‑tangent and force‑radial diagram, and derives \(a_c = v^{2}/r\) on the board.
- Guided practice (12'): Work through the stone‑on‑string example together, highlighting each substitution step.
- Hands‑on demo (8'): Students swing a mass on a string, measure radius and speed, and calculate tension using the formula.
- Collaborative worksheet (10'): Groups answer conceptual questions and complete a short problem on a banked curve.
- Check for understanding (5'): Whole‑class polling (e.g., Kahoot) on why a perpendicular force does not change speed.
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Conclusion:
Summarise that a constant‑magnitude force perpendicular to motion provides the necessary centripetal acceleration without altering speed. Ask each student to write one real‑world example on an exit ticket and explain the force involved. Assign homework: complete the additional problem set on circular motion and prepare a short explanation of why friction is not required on a properly banked road.
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