Angular Momentum and its Conservation

Download the Lessonotes Mobile Liberia app for faster lesson access on Android and iPhone.

Subject: Physics

Semester: 1

Period: 3

Week: 16

---

School Name:

Teacher’s Name:

Subject: Physics

Grade Level: Grade 11

Week & Period: Week 16, Period III

Date:

Sub-topic: Angular Momentum and Its Conservation

Learning Objectives:

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

1. Define angular momentum and its SI unit.
2. Distinguish between linear and angular momentum.
3. State and apply the law of conservation of angular momentum.
4. Solve problems involving angular momentum.
5. Identify real-world applications of angular momentum conservation.

 

Previous Knowledge:

Students understand linear momentum and its conservation from Weeks 13–15.

 

Instructional Materials:

• Rotating platform (lazy Susan or swivel stool)
• Dumbbells or small weights
• Meter rule
• Stopwatch
• String and masses
• Visuals of figure skaters, satellites, rotating fans

 

Anticipation (Warm-Up):

Ask learners:

• "Why does a spinning figure skater spin faster when pulling their arms in?"
• "Why do stars spin faster as they collapse into neutron stars?"

Short demo: Learner stands on rotating chair holding weights. As they pull weights inward, rotation speeds up.

 

Building Knowledge (Main Lesson) – 25 minutes

3. Differences Between Linear and Angular Momentum:

Feature	Linear Momentum	Angular Momentum
Equation	p=mv	L=Iω
Unit	kg·m/s	kg·m²/s
Vector Direction	Along motion	Perpendicular to plane of rotation
External Agent	Force	Torque

Worked Example:

Problem:
A student standing on a frictionless rotating platform with arms extended has a moment of inertia of 4.0 kg·m² and is rotating at 2 rad/s. When the student pulls in their arms, the moment of inertia becomes 2.0 kg·m². What is the new angular velocity?

Solution:

Experiment:

Title: Conservation of Angular Momentum Using a Swivel Chair

Materials:

• Swivel chair or rotating stool
• Two dumbbells or equal masses
• Stopwatch (optional)

Procedure:

1. Student sits on rotating chair holding weights with arms stretched.
2. Rotate gently and ask student to pull arms in.
3. Observe increase in rotation speed.

Observation:
Rotation becomes faster as moment of inertia decreases. Angular momentum remains conserved.

 

Learners’ Activities:

• Solve angular momentum problems from textbook.
• Perform rotating chair demonstration in groups.
• Identify applications in space, sports, or machinery.

 

Consolidation (Review and Assessment) – 10 minutes

Oral Questions:

• What is angular momentum?
• How is it different from linear momentum?
• What happens to angular velocity when a spinning body reduces its radius?

 

Homework / Assignment:

• A spinning disk with moment of inertia 10 kg·m² rotates at 5 rad/s. What is its angular momentum?
• Research 3 real-life situations where angular momentum is conserved.

 

Notes – Detailed and Explained:

• Angular momentum applies to all rotating objects.
• Moment of inertia depends on mass distribution.
• Conservation principle is critical in satellites, skaters, collapsing stars, wind turbines.
• Torque is to angular motion what force is to linear motion.

Differentiation:

• Visual: diagrams, rotation videos
• Kinesthetic: chair rotation demo
• Auditory: group discussions and guided solving

 

Teacher’s Reflection:

• Did learners grasp the relationship between moment of inertia and velocity?
• Were they able to apply conservation principles in problem-solving?
• Should real-life applications be emphasized more?