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# NCERT Solutions Class 11 Physics Chapter 4 Laws Of Motion - PDF Download

Class 11 NCERT Solutions for Class 11 Physics Chapter 4 Laws of Motion is one of the key tools to prepare Physics efficiently for board examination. Using NCERT Solutions will help you to get an idea about the question paper pattern and the marking scheme of the exam.

In the last chapter, we mainly focused on the motion of a particle. We have seen that uniform motion depends on velocity, whereas non-uniform motion depends on acceleration..Now, this becomes a basic question in this chapter. To learn all the basic concepts covered in this chapter, NCERT Solutions for Class 11 Physics are designed with accurate and authentic information strictly based on the latest board exam Syllabus for 2023-24 and its curriculum. Let’s have a look at chapter 4 laws of motion Class 11 solutions.

## Topics of Class 11 Physics Chapter 4 Laws of Motion

Some of the topics and subtopics covered in the NCERT Solutions for Class 11 Physics Chapter 4 are mentioned below.

 Section Number Topic 4.1 Introduction 4.2 Aristotle’s fallacy 4.3 The Law of inertia 4.4 Newton’s First Law Of Motion 4.5 Newton’s Second Law of Motion 4.6 Newton’s Third Law of Motion 4.7 Conservation of Momentum 4.8 Equilibrium Of A Particle 4.9 Common Forces In Mechanics 4.10 Circular Motion 4.11 Solving problems in mechanics

### Introduction

In this chapter we will learn about the external force applied on objects.you can see many examples, numerical problems and experiments in this chapter. Following example will give you a brief idea about this chapter: a stone released from the top of a building accelerates downward due to the gravitational force pull of the earth. A bar magnet can attract an iron nail from a certain distance. This shows that external agency forces (e.g. gravitational and magnetic forces ) can exert force on a body even from a distance. In short, a force is required to put a stationary or constant body in motion or stop a moving body, and some external force is needed to provide this force. The external force may or may not be in contact with the body.

### Aristotle’s Fallacy

Aristotle's Laws of Motion states that nothing moves unless you push it. [ it is moved by only a mover] Some motion is natural for the sublunar elements, rectilinear motion to or away from the earth's center for the supralunar quintessence, circular motion. All other motion is violent, and each requires a mover.

### The Law of Inertia

Galileo’s law of inertia states that starting point which he formulated as the first law of motion: Every body or object continues to be in its state of rest or of uniform motion in a straight line unless compelled by some external force to act otherwise.

To summarize this topic, if the net external force is zero, a body at rest continues to remain at rest and a body in motion continues to move with a uniform velocity. So, this property of the object is called inertia. Inertia means ‘resistance to change’. A body does not change its state of rest or uniform motion, unless an external force applied to it to change that state.

## Newton’s First Law Of Motion

The first law of motion expressed as: If the net external force on a body is zero, its acceleration is also zero. Acceleration can be non zero only if the net external force on the body.

## Newton’s Second Law of Motion

Newton's second law states that the acceleration of an object or body depends upon two variables one is: the net force acting on the object and the mass of the object. The acceleration of the body or object is directly proportional to the net force acting on the body and inversely proportional to the mass of the body.

Momentum of a body is defined to be the product of mass m and velocity v of a body, and is denoted by p:

p = m v

Momentum is a vector quantity.

## Newton’s Third Law of Motion

In this topic we will learn about the 3rd law of motion with various examples. In this topic there are so many examples that will explain the 3rd law of motion.

Third law of motion states that to every action, there is always an equal and opposite reaction.

### Conservation of Momentum

The law of conservation of momentum says that in an isolated system the total momentum of two or more objects acting upon each other remains constant unless an external force is applied on it. So, momentum can neither be created nor destroyed.

### Equilibrium Of A Particle

In this topic we will learn about equilibrium of a particle which states that when the net external force acting on a particle is zero, the particle is said to be in equilibrium. Applying Newton's First Law of Motion to this situation, we can say that the particle is either at rest or in uniform motion.

### Common Forces In Mechanics

We will learn a variety of forces as we study mechanics. There are mainly two categories of these forces are contact forces and non-contact forces. Following are some of the forces that are explained in detail: -

Contact Forces

1. When an object comes into contact with another object, a contact force forms. Mutual contact forces, which are consistent with Newton's Third Law of Motion, occur whenever two objects are in contact with each other.

2. "Normal Reaction" are standards to the portion of the contact force that is normal to the contact surfaces.

3. Moreover  "Friction" refers to the element that runs parallel to the surfaces. Even when solids and liquids are in direct touch with each other, a contact force can still exist.

1. A solid submerged in a liquid will experience buoyancy forces, air resistance, viscous forces, etc. as instances of contact forces.

Non-Contact Forces

1. A force that affects an object without making direct touch with it is known as a non-contact force.

2. Gravity, which bestows weight, is the best example of  non-contact force.

3. Gravitational force, Magnetic force, Electrostatics and the nuclear force are some of the examples of Non-Contact Force.

### Circular Motion

Circular motion is described as a movement of any object while rotating along a circular path. Circular motion can be either uniform or non-uniform so during uniform circular motion, the angular rate of rotation and speed will be constant, while during non-uniform motion the rate of rotation keeps changing.

## Benefits of NCERT Solutions for Class 11 Physics Chapter 4

Class 11 physics chapter 4 NCERT solutions is a tool for simplified learning of ch 4.

• The chapter of Law of motion Class 11 NCERT covers some of the most important topics, each of which is discussed in the PDF in a very simple and easy manner.

• Our NCERT Solutions for Class 11 Physics Chapter 4 Law of motion are prepared by highly skilled expert physics teachers who are masters in the subject. Our expert team of professionals also comprises lecturers and PhD holders.

• Good scores are important for every student; we understand that. Thus, our Class 11 Physics Chapter 4 NCERT solutions streamline your efforts into scoring the highest possible marks.

• A problem-solving approach with the help of NCERT physics Class 11 Chapter 4 Law of motion solutions will solidify the foundation of your knowledge of the basics.

Question 1: What are the topics of chapter 4 Law of motion?

Answer: Following are the topics and subtopics of chapter 4

4.1 Introduction

4.2 Aristotle’s fallacy

4.3 The Law of inertia

4.4 Newton’s First Law Of Motion

4.5 Newton’s Second Law of Motion

4.6 Newton’s Third Law of Motion

4.7 Conservation of Momentum

4.8 Equilibrium Of A Particle

4.9 Common Forces In Mechanics

4.10 Circular Motion

4.11 Solving problems in mechanics

Question 2 : What is Newton's first law of motion?

Answer: The first law of motion expressed as: If the net external force on a body is zero, its acceleration is also zero. Acceleration can be non zero only if the net external force on the body.