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NCERT Solutions Class 9 Science - Chapter 8 Force and Laws of Motion - PDF Download

JEE Mains & Advanced

NCERT Solutions for class 9 science chapter 8 Force and Laws of Motion is ready to help students to overcome their doubts and understand the concepts in detail. 

Class 9 solutions of science is a useful reference material that can help students to clear their doubts immediately in an effective manner. NCERT solutions for class 9 science are designed in a way that is easy for students and full of questions, activities and exercises that are focused on CBSE and competitive examination. 

The NCERT solutions for class 9 science are developed by subject experts & teaching faculty who have experience of coaching students. NCERT solution for class 9 science is developed with the concept based approach and the exact answer method for examination. It is a comprehensive and well structured concept based learning solution for imparting confidence to students for CBSE and competitive examinations.

NCERT Solutions for Class 9 Science Chapter 8 Topics

Section Name

Topic Name


Force and Laws of Motion


Balanced and unbalanced forces


First Law of Motion


Inertia and Mass


Second Law of Motion


Third Law of Motion

8.1 Balanced and Unbalanced Forces: Balanced forces: When a book rests on a table, its weight (gravity pulling it down) is equalized by the normal force of the table pushing it up. Unbalanced forces: When you press a book against a table, you are applying an unbalanced force to the book. The friction is against the book, but your force pushes past it, accelerating the book.

8.2 First Law of Motion: The first law of motion, also referred to as Newton's first law of motion or the law of inertia, is a fundamental principle of classical physics. The first law of motion was first proposed by Sir Isaac Newton. It describes the behavior of an object when no external force is acting on it. An object that is stationary will remain stationary, and an object that is moving will move at a constant speed unless it is affected by an unbalanced force.

8.3 Inertia and Mass: Inertia refers to an object's ability to withstand changes in its motion. Objects with a high degree of inertia are able to withstand changes in their speed and/or orientation, while objects with a low degree of inertia are more susceptible to acceleration or deceleration. Mass is a unit of measure that can be expressed in a number of different ways, such as kilograms or grams. Mass is a fundamental characteristic of an object that does not change regardless of its position or the forces that interact with it.

8.4 Second Law of Motion: Sir Isaac Newton's second law of motion is another fundamental law of classical physics. This law states that the speed of motion is proportional to the amount of force applied to the object, the mass of the object, and the acceleration that results from that force. The speed of motion is directly related to the amount of net force that is applied to the object. This force acts in a direction that causes the object's momentum to change over a period of time.

Subtopics covered in the section 8.4 Second Law of Motion: 

     8.4.1 Mathematical formulation of second law of motion

8.5 Third Law of Motion: Sir Isaac Newton's third law of motion, commonly referred to as Newton's third law, is a fundamental principle of classical physics. This law outlines the relationship between forces and interactions between two or more objects, and is often associated with the phrase "for every action there is an equivalent and opposite reaction."

Key Features of Class 9 Science Chapter 8

  • The first law of motion is that an object is stationary or moving in a straight line unless an unbalanced force is applied to it.

  • The second law of motion states that the rate of change of an object’s momentum is proportional to the direction of the unbalanced force applied.

  • Inertia is the natural tendency of an object to resist any change in its state of rest or uniform motion.

  • The SI unit of measure for inertia is the kg.

  • Force of friction always prevents motion of an object.

  • The SI unit of measure for force is the, also referred to as the Newton force and symbolized by the N. 

  • Additionally, the Third Law of Motion states that every action has an equal and opposite reaction and is performed on two different bodies.

Benefits of Downloading the PDF of NCERT Solutions Class 9 Science Chapter 8 Force and Laws of Motion

Downloading the pdf of NCERT solutions for class 9 science chapter 8 “Force and laws of motion” can provide you with the following advantages:

Comprehensive solutions: NCERT solutions provide detailed and precise answers to all the questions of the textbook. This will help you to understand the concepts & principles of force & motion in detail.

Easy access: Having the pdf on your device means that you can easily access the solutions anytime and anywhere. It is not necessary to have an internet connection in order to study.

Clear explanations: The solutions provide clear explanations for every question. This will make it easier for you to understand the basic concepts of force & motion and the laws related to them. 

Homework and Assignments: These solutions can be used as a reference when working on homework and assignments related to chapter 8. They can help you to check your answers and make sure that they are correct. 

Exam Preparation: NCERT solutions can be very helpful during exam preparation as they provide step by step explanations and guidance to solve various types of questions which will help you to practice.

Time Effectiveness: PDF solutions save you time because you don’t have to spend time searching for solutions elsewhere. You can spend more time studying and practicing instead.

Self Assessment: After completing the exercises in your textbook, you can compare your answers to the solutions to assess your performance and find areas that need improvement.

Frequently Asked Questions

Question 1: What is Momentum?

Answer 1: The momentum of an object is the product of its mass and its velocity, and is a vector quantity. It is conserved when no external forces are present.

Question 2: What is meant by action and reaction forces?

Answer 2: Newton's Third Law states that all action forces have equal and opposite reaction forces. When one force is applied to another force, the second force is applied to the first force in the opposite direction.