Lesson Plan

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Lesson Plan
Grade: Date: 18/01/2026
Subject: Physics
Lesson Topic: Determine the resultant of two or more forces acting along the same straight line
Learning Objective/s:
  • Describe the concept of resultant force for collinear forces.
  • Apply a consistent sign convention to determine the net force on an object.
  • Calculate the resultant force using signed magnitudes and interpret its direction.
  • Identify common errors when combining forces and correct them.
Materials Needed:
  • Whiteboard and markers
  • Projector with slides showing force diagrams
  • Printed worksheets with practice problems
  • Spring scales or force sensors for a quick demo
  • Ruler or meter stick for drawing vectors
 Introduction:
Begin with a quick demonstration: pull a small cart with two strings in opposite directions and ask students what they observe. Recall that forces are vectors and that their direction matters when they act along the same line. Explain that by the end of the lesson they will be able to determine the resultant force and predict the motion of the object.
Lesson Structure:
  1. Do‑now (5’) – Students answer a short question on the board about positive/negative directions for forces; teacher checks answers.
  2. Mini‑lecture (10’) – Review key concepts (force, resultant, sign convention) using projector slides and the sled example.
  3. Guided practice (12’) – Work through the worked example together, filling the table and calculating the resultant.
  4. Collaborative activity (15’) – In pairs, students use spring scales to apply two forces on a cart, record magnitudes, assign signs, and compute the net force.
  5. Independent practice (10’) – Worksheet with the four practice questions; teacher circulates to address misconceptions.
  6. Quick check (3’) – Exit ticket: one sentence describing how to decide the direction of the resultant.
Conclusion:
Summarise that the resultant of collinear forces is found by choosing a positive direction, assigning signs, adding the values, and interpreting the sign of the sum. Remind students to double‑check their sign choices to avoid common mistakes. For homework, assign two additional textbook problems requiring them to draw force diagrams and calculate the net force.