CBSE Class 11 Physics Revision Notes Chapter 7

Class 11 Physics Revision Notes for Chapter 7 – Systems of Particles and Rotational Motion

Students can upgrade their exam preparations with Extramarks’ Class 11 Physics Chapter 7 Notes. Subject matter experts have produced these notes to give the students a thorough understanding of the chapter. One of the few accurate and dependable study resources that are available online is this set of  Chapter 7 Physics Class 11 Notes.

Each concept is thoroughly explained in these notes as the study is based on observation and applications. Students who refer to CBSE class 11 Physics Chapter 7 Notes will have a conceptual and clearer understanding of the workings mentioned in the chapter. Students can consult the Class 11 Physics Chapter 7 Notes for explanations of each concept and its applications.

Class 11 Physics Chapter 7 Notes

Unit V includes a chapter on the Motion of Systems and Particles. It deals with rotational motion and the system of particles. Along with Unit IV and Unit VI, this chapter carries a total mark distribution of 17 in the final examination. This chapter, which discusses the system of particles and rotational motion, is solely comprehension-based. The following topics are covered in the Notes of Class 11 Physics Chapter 7:

  • Centre of mass and its motion.
  • Centre of mass of a 2 particle system, rigid body and a uniform rod.
  • The momentum of force and momentum conservation.
  • Torque.
  • Moment of Inertia.
  • Angular momentum and laws of conservation of momentum.
  • The radius of gyration.
  • Parallel and perpendicular axis theorem.

Notes of System of Particles and Rotational Motion

The succinct explanations of some key ideas and subjects covered in the chapter are provided below. Refer to the Class 11 notes on the system of particles and rotational motion for a thorough understanding of the subject.

  • Centre of Mass

The location where a body’s entire mass is said to be concentrated is known as the centre of mass. It is also described as the system’s equilibrium point. The body is said to remain unaffected if any external force is applied to the centre of mass. It implies that the body will remain at rest if it is, and that the speed of a body in motion will not change.

For the centre of mass of a two particle system in motion,

v =m1v1+m2v2/m1+m2

a =m1a1+m2a2/m1+m2

Where,

v = Velocity of the centre of mass.

a =  Acceleration of the centre of mass.

  • Torque

The turning effect of a force on a fixed axis is known as torque. It also goes by the name “moment of force.” The torque SI unit is Nm. 

τ= r × F = rFSinθ

Where,

τ = Moment of force or torque

r̅ = Perpendicular distance

F̅ = Force

θ = Angle between the two vectors, r and F

Angular momentum can also be used to determine torque. Following is a definition of the relationship between torque and angular momentum: 

τ = dL/dt

  • Moment of Inertia

The phenomenon known as the moment of inertia describes how a rotating body resists changes in rotational motion. According to mathematics, it is determined by multiplying the particle mass by the distance from the axis of rotation. It is also known as the body’s rotational inertia.

FAQs (Frequently Asked Questions)

According to the Parallel Axis Theorem, a body’s moment of inertia is equal to the sum of its moments of inertia about its centre of mass and Ma2, where M is the body’s mass and a is the perpendicular distance between both the axes. The moment of inertia of a body along a perpendicular axis can be calculated using the Perpendicular Axis Theorem by adding the moments of inertia of the body about two axes that are perpendicular to one another and intersect where the perpendicular axis passes.

Centre of Mass: In order to describe the motion of the body as a particle, the term “centre of mass” is used. It is defined as the location where the total mass of the body is thought to be concentrated. This is not a part of the object. Centre of Gravity: The location where the body’s total weight is thought to be concentrated, where the gravitational force that results in all the body’s constituent particles acts. It can be found anywhere in the body of the object.

The product of the square of the distance from the axis and the mass of each particle makes up the moment of inertia of a body rotating about its axis.

Knowing how much force the body would require to slow down, accelerate or stop is helpful.

The following variables influence the moment of inertia of a body rotating about its axis:

  • Body’s distance from the axis.
  • Mass distribution of the body.