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NCERT Class 11 Physics Chapter 6: System of Particles and Rotational Motion PDF Download

System of Particles and Rotational Motion is Chapter 6 of the Class 11 Physics NCERT textbook. This chapter takes things a step forward by introducing motion not just in a straight line, but around an axis. It explains how systems of multiple particles move together, how to calculate centre of mass, and what happens when

NCERT Class 11 Physics Chapter 6: System of Particles and Rotational Motion

System of Particles and Rotational Motion is Chapter 6 of the Class 11 Physics NCERT textbook. This chapter takes things a step forward by introducing motion not just in a straight line, but around an axis. It explains how systems of multiple particles move together, how to calculate centre of mass, and what happens when rigid bodies rotate. Concepts like torque, angular momentum, and the famous Newton’s laws in rotational form are introduced in this chapter.

I decided to write about this chapter because many students find it difficult at first, but once understood, it becomes one of the most scoring topics in Physics. This chapter has strong connections to real life — from wheels rotating to athletes spinning in sports. Also, questions from this topic are regularly asked in JEE, NEET and board exams. Understanding this chapter properly helps in tackling chapters like Gravitation and Oscillations later. Since the NCERT book is the best place to start, having access to the full PDF along with a clear explanation of the content makes it easier to revise and practice.

NCERT Class 11 Physics Chapter 6: System of Particles and Rotational Motion – Overview

This chapter begins by dealing with systems of particles and then moves into the concepts of rotational motion in rigid bodies. It combines the ideas of mass, motion, forces and rotation, giving a solid base for further Physics study.

Key Topics Covered

1. Centre of Mass

  • What is centre of mass
  • Motion of centre of mass
  • Centre of mass of two/more particles
  • Centre of mass of rigid bodies

2. Linear Momentum and Angular Momentum

  • Conservation of linear momentum
  • Torque and angular momentum
  • Angular momentum in vector form
  • Conservation laws

3. Moment of Inertia

  • Definition and significance
  • Radius of gyration
  • Theorems of perpendicular and parallel axes
  • Calculation of moment of inertia for simple objects (rod, disc, ring, sphere)

4. Rotational Dynamics

  • Torque as the rotational equivalent of force
  • Newton’s second law for rotation
  • Rolling motion
  • Relationship between angular and linear quantities

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Click here to download NCERT Class 11 Physics Chapter 6: System of Particles and Rotational Motion PDF

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NCERT Class 12 English Flamingo Chapter 3: Deep Water PDF Summary & Download Link

Deep Water by William Douglas is the third chapter in the Class 12 English Flamingo book. It is an autobiographical piece where the author talks about his fear of water and how he overcame it. This is not just a story about swimming, but about fear, courage, determination, and personal growth. Douglas takes us through

NCERT Class 12 English Flamingo Chapter 3: Deep Water

Deep Water by William Douglas is the third chapter in the Class 12 English Flamingo book. It is an autobiographical piece where the author talks about his fear of water and how he overcame it. This is not just a story about swimming, but about fear, courage, determination, and personal growth. Douglas takes us through a terrifying experience from his childhood and shows us how he faced the same fear again and again till he conquered it completely.

I decided to write about Deep Water because it’s not just useful for students to score in their board exams, but it also gives a strong life lesson. Many students—like me—face some form of fear, whether it’s stage fright, fear of exams, or even fear of failure. This chapter teaches that fear is natural, but it should not control our life. I personally feel this story helps students relate to their own struggles and motivates them to keep trying. It’s a reminder that real strength is not about being fearless, but about fighting the fear till it goes away. That’s why I think this chapter deserves to be discussed in detail.

Summary of Deep Water

Deep Water is a first-person account written by William Douglas, a former judge of the US Supreme Court. The story is a reflection on an incident that happened in his childhood and how it shaped his confidence and mindset later in life.

Main Points:

  • The Beginning of Fear:
    Douglas was afraid of water from the age of three when he was knocked over by waves at a beach in California. That memory stayed with him.
  • A Worse Incident:
    When he was ten or eleven, he went to a swimming pool at YMCA in Yakima. One day, a big boy picked him up and threw him into the deep end of the pool for fun. Douglas sank like a stone and thought he was going to die. He tried to come up but failed. That moment left a deep scar in his mind.
  • Struggling with Fear:
    After that, he avoided water completely. Even though he loved fishing and other outdoor activities, his fear of drowning stopped him.
  • Overcoming the Fear:
    Later, Douglas hired a swimming instructor. The instructor taught him each part of swimming slowly—from floating to breathing to kicking. Over several months, Douglas learned to swim again.
  • Final Victory:
    Even after learning to swim, he tested himself alone in lakes and rivers to be sure that the fear was really gone. He realised that once fear is faced and challenged, it disappears.

Themes and Life Lessons

The chapter is much more than a childhood story. Here are the main lessons and messages from Deep Water:

  • Face Your Fears:
    Fear grows when we avoid it. But once we decide to face it, we become stronger than the fear itself.
  • Courage is a Process:
    Douglas didn’t become brave overnight. It took time, effort, and patience.
  • Mental Strength:
    The story shows how mental training is just as important as physical training.
  • Personal Growth:
    The author not only learned swimming but also grew as a person. This incident gave him the courage to face bigger challenges in life.

Character Sketch of William Douglas

Character TraitDescription
FearfulAs a child, he was deeply scared of water due to a bad experience.
DeterminedInstead of living with fear, he chose to fight it.
HonestHe openly shares his fear and how it affected him.
InspiringHis story motivates readers to fight their own fears and never give up.

Exam Preparation Tips for Deep Water

Here are some common question types based on this chapter:

Question TypeExamples
Short AnswerWhat made Douglas fear water at first?
Long AnswerHow did Douglas overcome his fear of water? What did he learn from the experience?
Value-BasedWhy is the story called “Deep Water”? What does it symbolise?
Extract-Based“The instructor was finished. But I was not finished.” – Explain this line.

Tip: Try to connect the answers to real-life situations. Use keywords like fear, courage, practice, transformation when writing long answers.

Download PDF – NCERT Class 12 Flamingo Chapter 3

To read the full chapter Deep Water, you can download the official PDF from this website. It’s free and safe to use for all students.

NCERT Class 12 English Flamingo Chapter 3: Deep Water

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