Parallel Forces and Moments (Torque)

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Subject: Physics

Semester: 1

Period: 2

Week: 9

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School Name:

Teacher’s Name:

Subject: Physics

Grade Level: Grade 11

Week & Period: Week 9, Period II

Date:

Sub-topic: Parallel Forces and Moments (Torque)

Learning Objectives

By the end of this lesson, learners should be able to:

1. Understand and calculate resultant of parallel forces.
2. Define and calculate moments (torques) about a pivot.
3. Understand and apply the principle of moments in equilibrium.
4. Identify practical applications of moments.

 

Previous Knowledge

Basic force addition and equilibrium.

 

Instructional Materials

• Meter sticks or rigid rods
• Weights of different masses
• Supports or pivots
• Spring balances

 

Anticipation (Warm-Up) – 5 minutes

Ask:

• “How do seesaws balance?”
• “What does it mean to ‘turn’ an object around a point?”

 

Building Knowledge (Main Lesson) – 25 minutes

1. Parallel Forces:

• Forces acting in the same or opposite directions along parallel lines.
• Resultant magnitude is the algebraic sum.
• Resultant line of action found by taking moments.

2. Moments (Torque):

• Moment = Force × Perpendicular distance from pivot.
• Unit: Newton-meter (Nm)

3. Principle of Moments:

• For equilibrium, sum of clockwise moments = sum of anticlockwise moments.

 

Example Calculation:

Two forces 30 N and 40 N act parallel on a beam 2 m apart. Calculate resultant force and position from the 30 N force.

Learners’ Activities

• Use a meter stick on a pivot and hang weights.
• Calculate moments and resultant forces.
• Verify the principle of moments experimentally.

 

Consolidation (Review and Assessment) – 10 minutes

Oral Questions:

• Define moment of force.
• Calculate moment of 50 N force acting 0.5 m from pivot.
• Explain how seesaws balance using moments.

 

Homework / Assignment

• Two weights of 25 N and 35 N act 1.5 m apart. Find resultant force and its position relative to 25 N force.
• Explain with example the principle of moments.

 

Notes – Detailed and Explained

• Moments cause rotation about a point.
• Principle of moments is fundamental in mechanics and engineering.
• Practical applications include levers, seesaws, and bridges.

 

Expanded Notes / Instructions

• Use diagrams extensively.
• Reinforce with hands-on experiments.

 

Inclusive / Differentiation

• Group practicals for social learners.
• Visual aids and stepwise calculation guidance.

 

Teacher’s Reflection

• Was the moment concept clearly understood?
• Did practical demonstration improve grasp?