Lesson Plan

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Lesson Plan
Grade: Date: 17/01/2026
Subject: Physics
Lesson Topic: define the radian and express angular displacement in radians
Learning Objective/s:
  • Define a radian as the angle subtended by an arc equal to the radius.
  • Derive and apply the relationship s = rθ for arc length.
  • Convert accurately between radians and degrees.
  • Calculate angular displacement in radians from a given arc length.
  • Solve circular‑motion problems using radian measures.
Materials Needed:
  • Projector or interactive whiteboard
  • Slides with diagrams of circles and radian definitions
  • Worksheet with practice problems
  • String or ruler for hands‑on demonstration
  • Calculator for conversions
  • Whiteboard and markers
 Introduction:
Begin with a quick visual of a wheel turning and ask students how we could measure the amount it has turned. Recall that angles are often measured in degrees, but today we will explore the SI unit, the radian, which links angles directly to arc length. By the end of the lesson students will be able to express angular displacement in radians and convert it to degrees.
Lesson Structure:
  1. Do‑now (5'): Students answer a short question on the difference between degrees and radians.
  2. Teacher input (10'): Define the radian, show the diagram, derive s = rθ.
  3. Guided practice (10'): Convert several angles between degrees and radians using 2π rad = 360°.
  4. Hands‑on activity (10'): Use string and a drawn circle to measure an arc equal to the radius, confirming one radian.
  5. Application problem (10'): Solve the wheel example, finding angular displacement in radians and degrees.
  6. Check for understanding (5'): Exit ticket – write the formula Δθ = Δs / r and a conversion factor.
Conclusion:
Summarise that a radian ties the angle to the radius through the simple s = rθ relationship and that conversions rely on 2π rad = 360°. For the exit ticket, students write the radian‑to‑degree conversion factor. Homework: complete a worksheet converting common angles and solving two angular‑displacement problems.