case study questions class 9 science pdf gravitation

Case Study Questions Class 9 Science Gravitation

Case study questions class 9 science chapter 10 gravitation, cbse case study questions class 9 science – gravitation.

(3) Archimedes’ principle, stated as follows: When a body is immersed fully or partiallyin a fluid, it experiences an upward force thatis equal to the weight of the fluid displacedby it. The upward force is known as up thrust or buoyant force. In fact, all objects experience a force of buoyancy when they are immersed in a fluid. The magnitude of this buoyant force depends on the density of the fluid.Objects having density less than that of the liquid in which they are immersed float on the surface of the liquid. If the density of the object is more than the density of the liquid in which it is immersed then it sinks in the liquid. Hence body will float or sink depends upon difference between density of body and fluid.

(5) The force acting on an object perpendicular to the surface is called thrust. When you stand on loose sand, the force, that is, the weight of your body is acting on an area equal to area of your feet. When you lie down then the same force acts on an area equalto the contact area of your whole body, which is larger than the area of your feet. Thus, the effects of forces of the same magnitude on different areas are different. In the above cases, thrust is the same. But effects are different. Therefore the effect of thrust depends on the area on which it acts. The effect of thrust on sand is larger while standing than while lying. The thrust on unit area is called pressure.

(c) Both a and b

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Case Study Questions of Class 9 Science PDF Download

Download PDF Case Study Questions of Class 9 Science to prepare for the upcoming CBSE Class 9 Exams Exam 2023-24. With the help of our well-trained and experienced faculty, we provide solved examples and detailed explanations for the recently added  Class 9 Science case study questions .

Case study questions are based on real or hypothetical scenarios that require students to analyze, evaluate, and apply scientific concepts to solve problems or make informed decisions. They often present a detailed context, providing students with the opportunity to demonstrate their understanding of the subject matter beyond basic recall.

Table of Contents

Class 9 Science: Case Study Questions

The inclusion of case study questions in Class 9 science CBSE is a great way to engage students in critical thinking and problem-solving. By working through real-world scenarios, Class 9 Science students will be better prepared to tackle challenges they may face in their future studies and careers. Class 9 Science Case study questions also promote higher-order thinking skills, such as analysis and synthesis. In addition, case study questions can help to foster creativity and innovation in students. As per the recent pattern of the Class 9 Science examination, a few questions based on case studies/passages will be included in the CBSE Class 9 Science Paper. There will be a paragraph presented, followed by questions based on it.

Chapterwise Case Study Questions of Class 9 Science

• Case Study Questions for Chapter 1 Matter in Our Surroundings
• Case Study Questions for Chapter 2 Is Matter Around Us Pure?
• Case Study Questions for Chapter 3 Atoms and Molecules
• Case Study Questions for Chapter 4 Structure of Atom
• Case Study Questions for Chapter 5 The Fundamental Unit of Life
• Case Study Questions for Chapter 6 Tissues
• Case Study Questions for Chapter 7 Diversity in Living Organisms
• Case Study Questions for Chapter 8 Motion
• Case Study Questions for Chapter 9 Force and Laws of Motion
• Case Study Questions for Chapter 10 Gravitation
• Case Study Questions for Chapter 11 Work and Energy
• Case Study Questions for Chapter 12 Sound
• Case Study Questions for Chapter 13 Why do we Fall ill
• Case Study Questions for Chapter 14 Natural Resources
• Case Study Questions for Chapter 15 Improvement in Food Resources

You can find a wide range of solved case studies on cbseexperts, covering various topics and concepts. Class 9 Science case studies are designed to help you understand the application of various concepts in real-life situations.

Class 9 Science Syllabus

Unit I: Matter-Nature and Behaviour

 Definition of matter; solid, liquid, and gas; characteristics – shape, volume, density; change of statementing (absorption of heat), freezing, evaporation (cooling by evaporation), condensation, sublimation.

Nature of matter:  Elements, compounds, and mixtures. Heterogeneous and homogenous mixtures, colloids, and suspensions. Physical and chemical changes (excluding separating the components of a mixture).

Particle nature and their basic units:  Atoms and molecules, Law of Chemical Combination, Chemical formula of common compounds, Atomic and molecular masses.

Structure of atoms:  Electrons, protons and neutrons, Valency, Atomic Number and Mass Number, Isotopes and Isobars.

Unit II: Organization in the Living World

Cell – Basic Unit of life:  Cell as a basic unit of life; prokaryotic and eukaryotic cells, multicellular organisms; cell membrane and cell wall, cell organelles and cell inclusions; chloroplast, mitochondria, vacuoles, endoplasmic reticulum, Golgi apparatus; nucleus, chromosomes – basic structure, number.

Tissues, Organs, Organ System, Organism:  Structure and functions of animal and plant tissues (only four types of tissues in animals; Meristematic and Permanent tissues in plants).

Unit III: Motio n, Force,  and Work

Motion:  Distance and displacement, velocity; uniform and non-uniform motion along a straight line; acceleration, distance-time and velocity-time graphs for uniform motion and uniformly accelerated motion, elementary idea of uniform circular motion.

Force and Newton’s laws:  Force and Motion, Newton’s Laws of Motion, Action and Reaction forces, Inertia of a body, Inertia and mass, Momentum, Force and Acceleration.

Gravitation:  Gravitation; Universal Law of Gravitation, Force of Gravitation of the earth (gravity), Acceleration due to Gravity; Mass and Weight; Free fall. Floatation: Thrust and Pressure. Archimedes’ Principle; Buoyancy.

Work, Energy and Power:  Work done by a Force, Energy, power; Kinetic and Potential energy; Law of conservation of energy (excluding commercial unit of Energy).

Sound: Nature of sound and its propagation in various media, speed of sound, range of hearing in humans; ultrasound; reflection of sound; echo.

Unit IV: Food Production

Plant and animal breeding and selection for quality improvement and management; Use of fertilizers and manures; Protection from pests and diseases; Organic farming.

Books for Class 9 Science Exams

Benefits of Case Study Questions

• Enhancing Analytical Skills : Case study questions challenge students to analyze complex scenarios, identify relevant information, and derive meaningful insights. By engaging with these questions, students develop critical analytical skills that are essential for scientific thinking and problem-solving.
• Promoting Critical Thinking : Case study questions encourage students to think critically and evaluate different perspectives. They require students to reason, make logical deductions, and justify their answers with supporting evidence. This process helps in honing their critical thinking abilities, enabling them to approach problems from multiple angles.
• Encouraging Practical Application of Concepts : By presenting real-world or hypothetical situations, case study questions promote the application of scientific concepts in practical scenarios. This application-based approach fosters a deeper understanding of the subject matter and helps students see the relevance of what they learn in the classroom to everyday life.

Case study questions of Class 9 Science provide students with an opportunity to apply their knowledge, enhance analytical skills, and think critically. By understanding the format, benefits, and effective strategies for answering case study questions, students can excel in this form of assessment. While challenges may arise, practicing time management, improving information extraction skills, and enhancing observation abilities will enable students to overcome these obstacles and perform well. Embracing case study questions as a valuable learning tool can contribute to a holistic understanding of scientific concepts and foster problem-solving abilities.

1. What is the purpose of case study questions in Class 9 Science?

Case study questions serve the purpose of evaluating a student’s understanding of scientific concepts, their ability to apply knowledge in real-life situations, and their analytical and critical thinking skills.

2. How can case study questions help improve analytical skills?

Case study questions require students to analyze complex scenarios, identify relevant information, and derive meaningful insights. Regular practice with such questions can significantly enhance analytical skills.

3. Are case study questions difficult to answer?

Case study questions can be challenging due to their comprehensive nature and the need for critical thinking. However, with practice and effective strategies, students can develop the skills necessary to answer them effectively.

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Class 9 Science Case Study Questions

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Download the app to get CBSE Sample Papers 2023-24, NCERT Solutions (Revised), Most Important Questions, Previous Year Question Bank, Mock Tests, and Detailed Notes.

If you are wondering how to solve class 9 science case study questions, then myCBSEguide is the best platform to choose. With the help of our well-trained and experienced faculty, we provide solved examples and detailed explanations for the recently added Class 9 Science case study questions.

You can find a wide range of solved case studies on myCBSEguide, covering various topics and concepts. Class 9 Science case studies are designed to help you understand the application of various concepts in real-life situations.

The rationale behind Science

Science is crucial for Class 9 students’ cognitive, emotional, and psychomotor development. It encourages curiosity, inventiveness, objectivity, and aesthetic sense.

In the upper primary stage, students should be given a variety of opportunities to engage with scientific processes such as observing, recording observations, drawing, tabulating, plotting graphs, and so on, whereas in the secondary stage, abstraction and quantitative reasoning should take a more prominent role in science teaching and learning. As a result, the concept of atoms and molecules as matter’s building units, as well as Newton’s law of gravitation, emerges.

Science is important because it allows Class 9 Science students to understand the world around us. It helps to find out how things work and to find solutions to problems at the Class 9 Science level. Science is also a source of enjoyment for many people. It can be a hobby, a career, or a source of intellectual stimulation.

Case study questions in Class 9 Science

The inclusion of case study questions in Class 9 science CBSE is a great way to engage students in critical thinking and problem-solving. By working through real-world scenarios, Class 9 Science students will be better prepared to tackle challenges they may face in their future studies and careers. Class 9 Science Case study questions also promote higher-order thinking skills, such as analysis and synthesis. In addition, case study questions can help to foster creativity and innovation in students. As per the recent pattern of the Class 9 Science examination, a few questions based on case studies/passages will be included in the CBSE Class 9 Science Paper. There will be a paragraph presented, followed by questions based on it.

Examples of Class 9 science class case study questions

Class 9 science case study questions have been prepared by myCBSEguide’s qualified teachers. Class 9 case study questions are meant to evaluate students’ knowledge and comprehension of the material. They are not intended to be difficult, but they will require you to think critically about the material. We hope you find Class 9 science case study questions beneficial and that they assist you in your exam preparation.

The following are a few examples of Class 9 science case study questions.

Class 9 science case study question 1

• due to its high compressibility
• large volumes of a gas can be compressed into a small cylinder
• transported easily
• all of these
• shape, volume
• volume, shape
• shape, size
• size, shape
• the presence of dissolved carbon dioxide in water
• the presence of dissolved oxygen in the water
• the presence of dissolved Nitrogen in the water
• liquid particles move freely
• liquid have greater space between each other
• both (a) and (b)
• none of these
• Only gases behave like fluids
• Gases and solids behave like fluids
• Gases and liquids behave like fluids
• Only liquids are fluids

Answer Key:

• (d) all of these
• (a) shape, volume
• (b) the presence of dissolved oxygen in the water
• (c) both (a) and (b)
• (c) Gases and liquids behave like fluids

Class 9 science case study question 2

• 12/32 times
• 18 g of O 2
• 18 g of CO 2
• 18 g of CH 4
• 1 g of CO 2
• 1 g of CH 4 CH 4
• 2 moles of H2O
• 20 moles of water
• 6.022  ×  1023 molecules of water
• 1.2044  ×  1025 molecules of water
• (I) and (IV)
• (II) and (III)
• (II) and (IV)
• Sulphate molecule
• Ozone molecule
• Phosphorus molecule
• Methane molecule
• (c) 8/3 times
• (d) 18g of CH ​​​​​4
• (c) 1g of H ​​​​​​2
• (d) (II) and (IV)
• (c) phosphorus molecule

Class 9 science case study question 3

• collenchyma
• chlorenchyma
• It performs photosynthesis
• It helps the aquatic plant to float
• It provides mechanical support
• Sclerenchyma
• Collenchyma
• Epithelial tissue
• Parenchyma tissues have intercellular spaces.
• Collenchymatous tissues are irregularly thickened at corners.
• Apical and intercalary meristems are permanent tissues.
• Meristematic tissues, in its early stage, lack vacuoles, muscles
• (I) and (II)
• (III) and (I)
• Transpiration
• Provides mechanical support
• Provides strength to the plant parts
• None of these
• (a) Collenchyma
• (b) help aquatic plant to float
• (b) Sclerenchyma
• (d) Only (III)
• (c) provide strength to plant parts

Cracking Class 9 Science Case Study Questions

There is no one definitive answer to Class 9 Science case study questions. Every case study is unique and will necessitate a unique strategy. There are, nevertheless, certain general guidelines to follow while answering case study questions.

• To begin, double-check that you understand the Class 9 science case study questions. Make sure you understand what is being asked by reading it carefully. If you’re unclear, seek clarification from your teacher or tutor.
• It’s critical to read the Class 9 Science case study material thoroughly once you’ve grasped the question. This will provide you with a thorough understanding of the problem as well as the various potential solutions.
• Brainstorming potential solutions with classmates or other students might also be beneficial. This might provide you with multiple viewpoints on the situation and assist you in determining the best solution.
• Finally, make sure your answer is presented simply and concisely. Make sure you clarify your rationale and back up your claim with evidence.

A look at the Class 9 Science Syllabus

The CBSE class 9 science syllabus provides a strong foundation for students who want to pursue a career in science. The topics are chosen in such a way that they build on the concepts learned in the previous classes and provide a strong foundation for further studies in science. The table below lists the topics covered in the Class 9 Science syllabus of the Central Board of Secondary Education (CBSE). As can be seen, the Class 9 science syllabus is divided into three sections: Physics, Chemistry and Biology. Each section contains a number of topics that Class 9 science students must study during the course.

CBSE Class 9 Science (Code No. 086)

Theme: Materials Unit I: Matter-Nature and Behaviour Definition of matter; solid, liquid and gas; characteristics – shape, volume, density; change of state-melting (absorption of heat), freezing, evaporation (cooling by evaporation), condensation, sublimation. Nature of matter:  Elements, compounds and mixtures. Heterogeneous and homogenous mixtures, colloids and suspensions. Particle nature and their basic units:  Atoms and molecules, Law of constant proportions, Atomic and molecular masses. Mole concept: Relationship of mole to mass of the particles and numbers. Structure of atoms:  Electrons, protons and neutrons, valency, the chemical formula of common compounds. Isotopes and Isobars.

Theme: The World of the Living Unit II: Organization in the Living World Cell – Basic Unit of life:  Cell as a basic unit of life; prokaryotic and eukaryotic cells, multicellular organisms; cell membrane and cell wall, cell organelles and cell inclusions; chloroplast, mitochondria, vacuoles, endoplasmic reticulum, Golgi apparatus; nucleus, chromosomes – basic structure, number. Tissues, Organs, Organ System, Organism: Structure and functions of animal and plant tissues (only four types of tissues in animals; Meristematic and Permanent tissues in plants).

Theme: Moving Things, People and Ideas Unit III: Motion, Force and Work Motion:  Distance and displacement, velocity; uniform and non-uniform motion along a straight line; acceleration, distance-time and velocity-time graphs for uniform motion and uniformly accelerated motion, derivation of equations of motion by graphical method; elementary idea of uniform circular motion. Force and Newton’s laws:  Force and Motion, Newton’s Laws of Motion, Action and Reaction forces, Inertia of a body, Inertia and mass, Momentum, Force and Acceleration. Elementary idea of conservation of Momentum. Gravitation:  Gravitation; Universal Law of Gravitation, Force of Gravitation of the earth (gravity), Acceleration due to Gravity; Mass and Weight; Free fall. Floatation:  Thrust and Pressure. Archimedes’ Principle; Buoyancy. Work, energy and power:  Work done by a Force, Energy, power; Kinetic and Potential energy; Law of conservation of energy. Sound:  Nature of sound and its propagation in various media, speed of sound, range of hearing in humans; ultrasound; reflection of sound; echo.

Theme: Food Unit IV: Food Production Plant and animal breeding and selection for quality improvement and management; Use of fertilizers and manures; Protection from pests and diseases; Organic farming.

PRESCRIBED BOOKS:

• Science-Textbook for class IX-NCERT Publication
• Assessment of Practical Skills in Science-Class IX – CBSE Publication
• Laboratory Manual-Science-Class IX, NCERT Publication
• Exemplar Problems Class IX – NCERT Publication

myCBSEguide: A true helper

There are numerous advantages to using myCBSEguide to achieve the highest results in Class 9 Science.

• myCBSEguide offers high-quality study materials that cover all of the topics in the Class 9 Science curriculum.
• myCBSEguide provides practice questions and mock examinations to assist students in the best possible preparation for their exams.
• On our myCBSEguide app, you’ll find a variety of solved Class 9 Science case study questions covering a variety of topics and concepts. These case studies are intended to help you understand how certain principles are applied in real-world settings
• myCBSEguide is that the study material and practice problems are developed by a team of specialists who are always accessible to assist students with any questions they may have. As a result, students may be confident that they will receive the finest possible assistance and support when studying for their exams.

So, if you’re seeking the most effective strategy to study for your Class 9 Science examinations, myCBSEguide is the place to go!

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Class 9 Science Case Study Questions PDF Download

• Post author: studyrate
• Post published:
• Post category: class 9th
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Class 9 Science Case Study Questions play a crucial role in the field of science education as they provide real-life scenarios for students to analyze, apply their knowledge, and develop problem-solving skills. This article aims to present a comprehensive collection of case study questions for Class 9 Science , covering various topics and concepts.

Join our Telegram Channel, there you will get various e-books for CBSE 2024 Boards exams for Class 9th, 10th, 11th, and 12th.

CBSE Class 9 Science Exam will have a set of questions based on case studies in the form of MCQs. The CBSE Class 9 Science Question Bank on Case Studies, provided in this article, can be very helpful to understand the new format of questions. Share this link with your friends.

If you want to want to prepare all the tough, tricky & difficult questions for your upcoming exams, this is where you should hang out.  CBSE Case Study Questions for Class 9  will provide you with detailed, latest, comprehensive & confidence-inspiring solutions to the maximum number of Case Study Questions covering all the topics from your  NCERT Text Books !

Table of Contents

CBSE Class 9th SCIENCE Chapterwise Case Study Question & Solution

Case study questions provide students with real-life scenarios that require critical thinking and application of scientific concepts. They help students understand the practical application of scientific principles and develop problem-solving skills in various scientific disciplines.

Chapterwise Case Study Questions for Class 9 Science

Inboard exams, students will find the questions based on assertion and reasoning. Also, there will be a few questions based on case studies. In that, a paragraph will be given, and then the MCQ questions based on it will be asked. For Science subjects, there would be 5 case-based sub-part questions, wherein a student has to attempt 4 sub-part questions.

• Case Study Questions for Chapter 1 Matter in Our Surroundings
• Case Study Questions for Chapter 2 Is Matter Around Us Pure?
• Case Study Questions for Chapter 3 Atoms and Molecules
• Case Study Questions for Chapter 4 Structure of Atom
• Case Study Questions for Chapter 5 The Fundamental Unit of Life
• Case Study Questions for Chapter 6 Tissues
• Case Study Questions for Chapter 7 Diversity in Living Organisms
• Case Study Questions for Chapter 8 Motion
• Case Study Questions for Chapter 9 Force and Laws of Motion
• Case Study Questions for Chapter 10 Gravitation
• Case Study Questions for Chapter 11 Work and Energy
• Case Study Questions for Chapter 12 Sound
• Case Study Questions for Chapter 13 Why do we Fall ill
• Case Study Questions for Chapter 14 Natural Resources
• Case Study Questions for Chapter 15 Improvement in Food Resources

The above  Case studies for Class 9 Science  will help you to boost your scores as Case Study questions have been coming in your examinations. These CBSE Class 9 Science Case Studies have been developed by experienced teachers of schools.studyrate.in for the benefit of Class 10 students.

Class 9 Maths Case Study Questions

Benefits of Case Studies in Science Education

Case studies offer several advantages over traditional teaching methods. Here are some key benefits:

• Real-World Application : Case studies present authentic scenarios, enabling students to understand how scientific concepts are applied in real-life situations.
• Critical Thinking : Analyzing case studies requires students to think critically, make connections, and apply scientific knowledge to solve problems.
• Interdisciplinary Approach : Case studies often involve multiple scientific disciplines, fostering an interdisciplinary understanding of complex issues.
• Engagement and Active Learning : Case studies actively engage students in the learning process, promoting active participation, discussion, and collaboration.
• Skill Development : Case studies develop essential skills such as analytical thinking, problem-solving, and effective communication of scientific concepts.

Importance of Practicing Case Study Questions

Practicing case study questions is crucial for Class 9 Science students to enhance their understanding and application of scientific concepts. Here’s why it is important:

• Application of Knowledge : Case studies allow students to apply their theoretical knowledge to practical situations, bridging the gap between theory and real-world scenarios.
• Developing Analytical Skills : Analyzing case studies improves students’ ability to identify relevant information, make connections, and draw logical conclusions.
• Problem-Solving Skills : Case studies present complex problems that require students to think critically and develop effective problem-solving strategies.
• Enhanced Exam Performance : Practicing case study questions familiarizes students with the format and types of questions they may encounter in exams, leading to improved performance.

Subjects Covered in the Case Study Questions for Class 9 Science

The case study questions for Class 9 Science cover the following subjects:

• Motion and Forces
• Light and Reflection
• Electricity
• Matter and Its Properties
• Atoms and Molecules
• Structure of the Atom
• Chemical Reactions
• Cell: The Fundamental Unit of Life
• Diversity in Living Organisms
• Natural Resources

Tips for Approaching Case Study Questions

To tackle case study questions effectively, consider the following tips:

• Read Carefully : Pay close attention to the details provided in the case study, as they hold crucial information for solving the problem.
• Analyze Methodically : Break down the problem into smaller components and analyze each part systematically.
• Apply Relevant Concepts : Identify the scientific principles relevant to the case study and apply them appropriately.
• Consider Multiple Perspectives : Explore different angles and viewpoints while proposing solutions, taking into account various scientific factors.
• Provide Justifications : Support your answers with scientific explanations and logical reasoning to strengthen your responses.

The Class 9 Science Case Study Questions provided in this article serve as a valuable resource for students seeking to enhance their scientific knowledge and problem-solving skills. By practicing these case studies, students can develop a deeper understanding of scientific concepts and their practical applications. Embrace this opportunity to engage with real-world scenarios and strengthen your scientific acumen.

Q1: Are the Class 9 Science Case Study Questions aligned with the official curriculum?

Yes, the Class 9 Science Case Study Questions presented in this article are aligned with the official curriculum. They cover relevant topics and concepts that students need to study for their exams.

Q2: Can practicing case study questions alone guarantee success in Class 9 Science exams?

Practicing case study questions is an important part of exam preparation, but it should be complemented with a thorough understanding of the subject matter. It is advisable to study the concepts in detail, refer to textbooks, and engage in other learning activities to achieve success in exams.

Q3: Where I Can get Class 9 Science Case Study Questions ?

You can practice Class 9 Science Case Study Questions on schools.studyrate.in for free.

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NCERT Solutions for Class 9 Science Chapter 9 Gravitation

• 10th June 2023

NCERT Solutions for Class 9 Science Chapter 9 Gravitation provides detailed answers for all in-text and exercise Questions. These solutions contain an in-depth explanation of each topic involved in the chapter. Students studying in class 9 can access these solutions for free in PDF format.

All these solutions are prepared by expert teachers and updated for the current academic session. NCERT Solutions for Class 9 Science Chapter 9 Gravitation help students to understand the fundamental concepts given in class 9 Science textbook. We have prepared the answers to all the questions in an easy and well-structured manner. It helps students to grasp the chapter easily.

CBSE Class 9 Science Gravitation Intext Questions (Solved)

PAGE NO. 102

Question 1: State the universal law of gravitation .

Answer: The universal law of gravitation states that every object in the universe attracts every other object with a force called the gravitational force. The force acting between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. 

For two objects of masses m 1 and m 2 and the distance between them r, the force (F) of attraction acting between them is given by the universal law of gravitation as:

Question 2: Write the formula to find the magnitude of the gravitational force between the earth and an object on the surface of the earth. 

PAGE NO. 104

Question 1: What do you mean by free fall? 

Answer: Gravity of the Earth attracts every object towards its centre. When an object is released from a height, it falls towards the surface of the Earth under the influence of gravitational force. The motion of the object is said to have free fall. 

Question 2: What do you mean by acceleration due to gravity? 

Answer: When an object falls towards the ground from a height, then its velocity changes during the fall. This changing velocity produces acceleration in the object. This acceleration is known as acceleration due to gravity (g). Its value is given by 9.8 m/s 2 . 

PAGE NO. 106

Question 1: What are the differences between the mass of an object and its weight? 

Answer: 

Question 2: Why is the weight of an object on the moon (1/6)th its weight on the earth? 

Answer: Let M E be the mass of the Earth and m be an object on the surface of the Earth. Let R E be the radius of the Earth. According to the universal law of gravitation, weight W E of the object on the surface of the Earth is given by,

 Let M M and R M be the mass and radius of the moon. Then, according to the universal law of gravitation, weight W M of the object on the surface of the moon is given by:

Therefore, weight of an object on the moon is of its weight on the Earth. 

PAGE NO. 109

Question 1: Why is it difficult to hold a school bag having a strap made of a thin and strong string? 

Answer: It is difficult to hold a school bag having a thin strap because the pressure on the shoulders is quite large. This is because the pressure is inversely proportional to the surface area on which the force acts. The smaller is the surface area; the larger will be the pressure on the surface. In the case of a thin strap, the contact surface area is very small. Hence, the pressure exerted on the shoulder is very large. 

Question 2: What do you mean by buoyancy? 

Answer:  The upward force exerted by a liquid on an object immersed in it is known as buoyancy. When you try to immerse an object in water, then you can feel an upward force exerted on the object, which increases as you push the object deeper into water. 

Question 3: Why does an object float or sink when placed on the surface of water? 

Answer: If the density of an object is more than the density of the liquid, then it sinks in the liquid. This is because the buoyant force acting on the object is less than the force of gravity. On the other hand, if the density of the object is less than the density of the liquid, then it floats on the surface of the liquid. This is because the buoyant force acting on the object is greater than the force of gravity. 

PAGE NO. 110

Question 1: You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg? 

Answer: When you weigh your body, an upward force acts on it. This upward force is the buoyant force. As a result, the body gets pushed slightly upwards, causing the weighing machine to show a reading less than the actual value. 

Question 2: You have a bag of cotton and an iron bar, each indicating a mass of 100 kg when measured on a weighing machine. In reality, one is heavier than other. Can you say which one is heavier and why? 

Answer: The bag of cotton is heavier than an iron bar. This is because the surface area of the cotton bag is larger than the iron bar. Hence, a more buoyant force acts on the bag than that on an iron bar. This makes the cotton bag lighter than its actual value. For this reason, the iron bar and the bag of cotton show the same mass on the weighing machine, but actually the mass of the cotton bag is more than that of the iron bar. 

CBSE Class 9 Science Gravitation Exercise Questions and Answers

Question 1: How does the force of gravitation between two objects change when the distance between them is reduced to half? 

Answer: According to the universal law of gravitation, gravitational force (F) acting between two objects is inversely proportional to the square of the distance between them, i.e., 

Hence, if the distance is reduced to half, then the gravitational force becomes four times larger than the previous value.

Question 2: Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object? 

Answer: All objects fall on the ground with constant acceleration, called acceleration due to gravity (in the absence of air resistance). It is constant and does not depend upon the mass of an object. Hence, heavy objects do not fall faster than light objects.

Question 3: What is the magnitude of the gravitational force between the earth and a 1 kg object on its surface? (Mass of the earth is 6 × 10 24 kg and radius of the earth is 6.4 × 10 6 m). 

Answer: According to the universal law of gravitation, gravitational force exerted on an object of mass m is given by:

Question 4: The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth? Why? 

Answer: According to the universal law of gravitation, two objects attract each other with equal force, but in opposite directions. The Earth attracts the moon with an equal force with which the moon attracts the earth. 

Question 5: If the moon attracts the earth, why does the earth not move towards the moon? 

Answer: The Earth and the moon experience equal gravitational forces from each other. However, the mass of the Earth is much larger than the mass of the moon. Hence, it accelerates at a rate lesser than the acceleration rate of the moon towards the Earth. For this reason, the Earth does not move towards the moon. 

Question 6: What happens to the force between two objects, if (i) the mass of one object is doubled? (ii) the distance between the objects is doubled and tripled? (iii) the masses of both objects are doubled?

Answer: According to the universal law of gravitation, the force of gravitation between two objects is given by:

(i) F is directly proportional to the masses of the objects. If the mass of one object is doubled, then the gravitational force will also get doubled. 

(ii) F is inversely proportional to the square of the distances between the objects. If the distance is doubled, then the gravitational force becomes one-fourth of its original value. Similarly, if the distance is tripled, then the gravitational force becomes one-ninth of its original value. 

(iii) F is directly proportional to the product of masses of the objects. If the masses of both the objects are doubled, then the gravitational force becomes four times the original value. 

Question 7: What is the importance of universal law of gravitation? 

Answer: The universal law of gravitation proves that every object in the universe attracts every other object. 

Question 8: What is the acceleration of free fall?

Answer: When objects fall towards the Earth under the effect of gravitational force alone, then they are said to be in free fall. Acceleration of free fall is 9.8 ms −2 , which is constant for all objects (irrespective of their masses). 

Question 9: What do we call the gravitational force between the Earth and an object? 

Answer: Gravitational force between the earth and an object is known as the weight of the object. 

Question 10:  Amit buys few grams of gold at the poles as per the instruction of one of his friends. He hands over the same when he meets him at the equator. Will the friend agree with the weight of gold bought? If not, why? [Hint: The value of g is greater at the poles than at the equator]. 

Answer:  Weight of a body on the Earth is given by W = mg Where, m = Mass of the body  g = Acceleration due to gravity 

The value of g is greater at poles than at the equator. Therefore, gold at the equator weighs less than at the poles. Hence, Amit’s friend will not agree with the weight of the gold bought. 

Question 11: Why will a sheet of paper fall slower than one that is crumpled into a ball?

Answer: When a sheet of paper is crumbled into a ball, then its density increases. Hence, resistance to its motion through the air decreases and it falls faster than the sheet of paper. 

Question 12: Gravitational force on the surface of the moon is only (1/6)  as strong as gravitational force on the Earth. What is the weight in newtons of a 10 kg object on the moon and on the Earth? 

Answer: Weight of an object on the moon =  (1/6)× Weight of an object on the Earth   Also,   Weight = Mass × Acceleration  Acceleration due to gravity, g = 9.8 m/s 2   Therefore, weight of a 10 kg object on the Earth = 10 × 9.8 = 98 N  And, weight of the same object on the moon = (1/6) × 98 = 16.3 N

Question 13: A ball is thrown vertically upwards with a velocity of 49 m/s. Calculate:  (i)  the maximum height to which it rises.  (ii) the total time it takes to return to the surface of the earth. 

Answer: (i) According to the equation of motion under gravity v 2 − u 2 = 2gs  Where, u = Initial velocity of the ball  v = Final velocity of the ball  s = Height achieved by the ball  g = Acceleration due to gravity  At maximum height, final velocity of the ball is zero, i.e., v = 0 m/s and u = 49 m/s  During upward motion, g = − 9.8 m s −2   Let h be the maximum height attained by the ball.   Hence, using 𝑣 2 − 𝑢 2 = 2𝑔𝑠, we have,  

(ii) Let t be the time taken by the ball to reach the height 122.5 then according to the equation of motion v = u + at, we get

But, Time of ascent = Time of descent  Therefore, total time taken by the ball to return = 5 + 5 = 10 s 

Question 14: A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity just before touching the ground. 

Answer:  According to the equation of motion under gravity v 2 − u 2 = 2gs  Where,  u = Initial velocity of the stone = 0 m/s  v = Final velocity of the stone  s = Height of the stone = 19.6 m  g = Acceleration due to gravity = 9.8 ms −2  

Now using v 2 − u 2 = 2gs, we get v 2 − 0 2 = 2 × 9.8 × 19.6  ⇒ v 2 = 2 × 9.8 × 19.6 = 19.6) 2   ⇒ v = 19.6 ms −1   Hence, the velocity of the stone just before touching the ground is 19.6 ms −1 .  

Question 15: A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s 2 , find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone? 

Answer: According to the equation of motion under gravity v 2 − u 2 = 2gs  Where,  u = Initial velocity of the stone = 40 m/s  v = Final velocity of the stone = 0 m/s  s = Height of the stone   g = Acceleration due to gravity = −10 ms −2   Let h be the maximum height attained by the stone.  

Therefore, total distance covered by the stone during its upward and downward journey = 80 + 80 = 160 m  Net displacement during its upward and downward journey = 80 + (−80) = 0. 

Question 16: Calculate the force of gravitation between the earth and the Sun, given that the mass of the earth = 6 × 10 24 kg and of the Sun = 2 × 10 30 kg. The average distance between the two is 1.5 × 10 11 m. 

Answer: According to the universal law of gravitation, the force of attraction between the Earth and the Sun is given by

Hence, the force of gravitation between the Earth and the Sun is 3.57 × 10 22 𝑁

Question 17: A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. Calculate when and where the two stones will meet. 

Answer: Let the two stones meet after a time t. 

When the stone dropped from the tower  Initial velocity, u = 0 m/s  Let the displacement of the stone in time t from the top of the tower be s.   Acceleration due to gravity, g = 9.8 ms −2   From the equation of motion, 

Initial velocity, u = 25 ms −1   Let the displacement of the stone from the ground in time t be 𝑠′.   Acceleration due to gravity, g = −9.8 ms −2   Equation of motion, 

The combined displacement of both the stones at the meeting point is equal to the height of the tower 100 m. 

In 4 s, the falling stone has covered a distance given by (1) as 𝑠 = 4.9 × 4 2 = 78.4 𝑚 Therefore, the stones will meet after 4 s at a height (100 – 78.4) = 20.6 m from the ground.

Question 18: A ball thrown up vertically returns to the thrower after 6 s. Find  (a) the velocity with which it was thrown up,  (b) the maximum height it reaches, and  (c) its position after 4 s. 

Answer: (a) Time of ascent is equal to the time of descent. The ball takes a total of 6 s for its upward and downward journey.  Hence, it has taken 3 s to attain the maximum height. 

Final velocity of the ball at the maximum height, v = 0 m/s  Acceleration due to gravity, g = −9.8 ms −2 Using equation of motion, v = u + at, we have  0 = u + (−9.8 × 3)  ⇒ u = 9.8 × 3 ⇒ u = 29.4 m/s  Hence, the ball was thrown upwards with a velocity of 29.4 m/s. 

(b) Let the maximum height attained by the ball be h.  Initial velocity during the upward journey, u = 29.4 m/s  Final velocity, v = 0 m/s Acceleration due to gravity, g = −9.8 ms −2   Using the equation of motion, 

Hence, the maximum height is 44.1 m.

(c) Ball attains the maximum height after 3 s. After attaining this height, it will start falling downwards.   In this case,  Initial velocity, u = 0 m/s Position of the ball after 4 s of the throw is given by the distance travelled by it during its downward journey in 4 s − 3 s = 1 s. 

Now, total height = 44.1 m  This means the ball is 39.2 m (44.1 m − 4.9 m) above the ground after 4 seconds. 

Question 19: In what direction does the buoyant force on an object immersed in a liquid act? 

Answer: An object immersed in a liquid experiences buoyant force in the upward direction. 

Question 20: Why does a block of plastic released under water come up to the surface of water? 

Answer: Two forces act on an object immersed in water. One is the gravitational force, which pulls the object downwards, and the other is the buoyant force, which pushes the object upwards. If the upward buoyant force is greater than the downward gravitational force, then the object comes up to the surface of the water as soon as it is released within the water. Due to this reason, a block of plastic released under water comes up to the surface of the water. 

Question 21: The volume of 50 g of a substance is 20 cm 3 . If the density of water is 1 g cm −3 , will the substance float or sink? 

Answer: If the density of an object is more than the density of a liquid, then it sinks in the liquid. On the other hand, if the density of an object is less than the density of a liquid, then it floats on the surface of the liquid. 

The density of the substance is more than the density of water (1 g cm −3 ).  Hence, the substance will sink in water. 

Question 22: The volume of a 500 g sealed packet is 350 cm 3 . Will the packet float or sink in water if the density of water is 1 g cm −3 ? What will be the mass of the water displaced by this packet? 

Answer:  Density of the 500 g sealed packet

The density of the substance is more than the density of water (1 𝑔/𝑐𝑚 3 ). Hence, it will sink in water.  The mass of water displaced by the packet is equal to the volume of the packet, i.e., 350 g. 

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NCERT Solutions for Class 9 Science Chapter 10 Gravitation

NCERT Solutions Class 9 Science Chapter 10 Gravitation – Here are all the NCERT solutions for Class 9 Science Chapter 10. This solution contains questions, answers, images, step by step explanations of the complete Chapter 10 titled Gravitation of Science taught in class 9. If you are a student of class 9 who is using NCERT Textbook to study Science, then you must come across Chapter 10 Gravitation. After you have studied lesson, you must be looking for answers of its questions. Here you can get complete NCERT Solutions for Class 9 Science Chapter 10 Gravitation in one place. For a better understanding of this chapter, you should also see Chapter 10 Gravitation Class 9 notes , Science.

NCERT Solutions for Class 9 Science Chapter 10 Gravitation

Topics and Sub Topics in Class 9 Science Chapter 10 Gravitation:

• Gravitation
• Thrust and Pressure
• Archimedes’ Principle
• Relative Density

These solutions are part of NCERT Solutions for Class 9 Science . Here we have given NCERT Solutions for Class 9 Science Chapter 10 Gravitation.

In – Text Questions Solved

Questin 2. What do you mean by buoyancy? Answer:  The upward force exerted by any fluid (liquid, gas) on an object is known as upthrust or buoyancy.

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• RD Sharma Class 9 Solutions

Questin 3. Why does an object float or sink when placed on the surface of water? Answer:  The density of the objects and water decides the floating or sinking of the object in water. The density of water is 1 gm/cm3.

• If the density of an object is less than the density of water then the object will float.
• If the density of an object is more than the density of water then the object will sink.

Formulae Handbook for Class 9 Maths and Science Educational Loans in India

Class 9 Science NCERT Textbook – Page 142 Questin 1. You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg? Answer:  The weighing machine actually measures the weight of the body as the acceleration due to gravity ‘g’ is acting on the body. Hence the mass reading of 42 kg given by a weighing machine is same as the actual mass of the body. As mass is the quantity of inertia, it remains the same.

Questions From NCERT Textbook for Class 9 Science

Question 19. In what direction does the buoyant force on an object immersed in a liquid act? Answer:  The buoyant force on an object immersed in a liquid acts upwards, i.e. opposite to the direction of the force exerted by the object.

Question 20. Why does a block of plastic released under water come up to the surface of water? Answer. The floating or sinking of a body in the water is decided by the density of both the body and water’s buoyant force acting on the body by the liquid. The density of plastic is less than the water and the buoyant force exerted by water on the plastiq block is greater than the force exerted by plastic on the water.

NCERT Solutions for Class 9 Science Chapter 10 Gravitation and Floatation (Hindi Medium)

More Questions Solved 

NCERT Solutions for Class 9 Science Chapter 10 Multiple Choice Questions

Choose the correct option:

• The device used to measure the purity of milk is (a) hydrometer (b) lactometer (d) hygrometer (d) maltometer
• The cork floats while the nail sinks in the water, this is due to (a) density of cork is more than nail (b) density of nail is more than cork. (c) density of cork is less than the density of water. (d) density of iron is less than the density of water.
• The relative density of silver is 10.8 and the density of water is 1o 3 kg/m 2 . The density of silver is (a) 1.8 x 1o 4  N/m 3  (b) 10.8 x 1o 3 N/m 3 (c) 1.8 x 1o 4 kg/m 3 (d) 10.8 x 1o 4 kg/m 3
• Buoyant force exerted by different fluids on a given body is (a) same (b) different (c) zero  (d) negligible
• Liquid A is denser than liquid B, a body of wood is dipped in both the liquids? The buoyant force experienced by the body in (a) liquid A is more (b) liquid B is more (c) liquid A is less    (d) none of the above Answer. 1 -(b), 2—(c), 3—(b), 4-(b), 5—(a).

NCERT Solutions for Class 9 Science Chapter 10 Very Short Answer Type Questions

Question 1. What is the S.I. unit of thrust? Answer:  Newton.

Question 2. What is the S.I. unit of pressure? Answer:  The S.I. unit of pressure = N/m 2  = Pascal.

Question 3. Define thrust. Answer:  The net force exerted by a body in a particular direction is called thrust.

Question 4. Define pressure. Answer:  The force exerted per unit area is called pressure.

Question 5. Why is it easier to swim in sea water than in river water? Answer:  The density of sea water is more due to dissolved salts in it as compared to the density of river water. Hence the buoyant force exerted on the swimmer by the sea water is more which helps in floating and makes swimming easier.

Question 6. Why a truck or a motorbike has much wider tyres? Answer:  The pressure exerted by it can be distributed to more area, and avoid the wear and tear of tyres.

Question 7. Why are knives sharp? Answer:  To increase the pressure, area is reduced, As pressure ∝ 1/Area hence the pressure or force exerted on a body increases.

Question 8. Why is the wall of dam reservoir thicker at the bottom? Answer:  The pressure of water in dams at the bottom is more, to withstand this pressure the dams have wider walls.

Question 9. Why do nails have pointed tips? Answer:  The force exerted when acts on a smaller area, it exerts larger pressure. So the nails have pointed tips.

Question 10. While swimming why do we feel light? Answer:  The swimmer is exerted by an upward force by water, this phenomenon is called buoyancy and it makes the swimmer feel light.

Question 11. Define density and give its unit. Answer:  The density of a substance is defined as mass per unit volume. Its unit is kg/m 3 .

NCERT Solutions for Class 9 Science Chapter 10 Short Answer Type Questions

Question 1. A ship made of iron does not sink but the iron rod sinks in water, why? Answer:  The iron rod sinks due to high density and less buoyant force exerted by the water on it, but in case of ship the surface area is increased, the upthrust experienced by the body is more. So it floats on water

Question 2. Camels can walk easily on desert sand but we are not comfortable walking on the sand. State reason. Answer:  Camels feet are broad and the larger area of the feet reduces the force/ pressure exerted by the body on the sand. But when we have to walk on the same sand, we sink because the pressure exerted by our body is not distributed but is directional.

Question 3. What is lactometer and hydrometer? Answer:  Lactometer is a device used to find the purity of a given sample of milk. Hydrometer is a device used to find the density of liquids.

Question 4. The relative density of silver is 10.8. What does this mean? Answer:  It means that the density of silver is 10.8 times more than that of water. T

Question 6. State Archimedes’ principle. Answer:  Archimedes’ principle—When a body is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it. It is used in designing of ships and submarines.

Question 7. Two cork pieces of same size and mass are dipped in two beakers containing water and oil. One cork floats on water but another sink in oil. Why? Answer:  The cork floats on water because the density of cork is less than the density of water, and another cork sinks in the oil because the density of cork is more than the oil.

Question 8. What are fluids? Why is Archimedes’ principle applicable only for fluids? Give the application of Archimedes’ principle. Answer:  Fluids are the substances which can flow e.g., gases and liquids are fluids. Archimedes’ principle is based on the upward force exerted by fluids on any object immersed in the fluid. Hence it is applicable only for fluids. Applications of Archimedes’ principle:

• It is used in designing of ship and submarine.
• It is used in designing lactometer, used to determine the purity of milk,
• To make hydrometers, used to determine the density of liquids.

NCERT Solutions for Class 9 Science Chapter 10 Long Answer Type Questions

• Nails have pointed tips.
• Knives have sharp edges.
• Needles have pointed tips.

NCERT Solutions for Class 9 Science Chapter 10 Activity -Based Questions

Question 1.

• Take an empty plastic bottle. Close the mouth of the bottle with an airtight stopper. Put it in a bucket filled with water. You see that the bottle floats.
• Push the bottle into the water. You feel an upward push. Try to push it further down. You will find it difficult to push deeper and deeper. This indicates that water exerts a force on the bottle in the upward direction. The upward force exerted by the water goes on increasing as the bottle is pushed deeper till it is completely immersed.
• Now, release the bottle. It bounces back to the surface.
• Does the force due to the gravitational attraction of the earth act on this bottle? If so, why doesn’t the bottle stay immersed in water after it is released? How can you immerse the bottle in water?

Question 2.

• Take a beaker filled with water.
• Take an iron nail and place it on the surface of the water.
• Observe what happens.

Question 3.

• Take a piece of cork and an iron nail of equal mass.
• Place them on the surface of water.

Answer:  The iron nail sinks as.the density of nail is more and the downward force exerted on nail is more than the buoyant force. The cost floats as the density of cost is less and the buoyant force exerted on it is more than the downward force.

Question 4.

• Take a piece of stone and tie it to one end of a rubber string or a spring balance.

• Note the elongation of the string or the reading on the spring balance due to the weight of the stone.
• Now, slowly dip the stone in the water in a container as shown in Fig. (b).
• Observe what happens to the elongation of the string or the reading on the balance. Observations :
• In Fig. (a) the elongation of the string is 6 cm.
• In Fig. (b) when the stone is dipped in water the length of string reduced to 5 cm.
• The length of the string in case (b) decreases due to the upward force exerted by water on the stone called as buoyant force.

NCERT Solutions for Class 9 Science Chapter 10 Value-Based Questions

Question 1. A milkman sold his milk in the city and always carried lactometer with him. The customers trusted him and his business flourished. (a) What is lactometer? (b) What is the principle of working of lactometer? (c) What value of milkman is seen in this case? Answer. (a) Lactometer is a device that measures the purity of milk. (b) The principle of lactometer is ‘Archimedes’ principle’. It states that when a body is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it. (c) Milkman is very honest and trustworthy.

Question 2. Reeta was wearing a high heel shoe for a beach party, her friend told her to wear flat shoes as she will be tired soon with high heels and will not feel comfortable, (a) Why would one feel tired with high heel shoes on beach? (b) Give the unit of pressure. (c) What value of Reeta’s friend is seen in the above act? Answer: (a) The high heel shoes would exert lot of pressure on the loose sand of beach and will sink more in the soil as compared to flat shoes. Hence large amount of force will be required to walk with heels. (b) Unit of pressure is Pascal. (c) Reeta’s friend showed the value of being helpful, concerned and intelligent.

Question 3. In the school fair, there was a game in which one need to find the heaviest ball without holding them in hand. Three balls were given and few disposable glasses were kept. Tarun saw his friend struggling to win the game but he was unable to find the heaviest ball. Tarun helped him by dipping the three balls one by one in the glass’es full of water upto the brim and finally they won the game. (a) Why did Tarun told his friend to dip the balls one by one in completely filled glass of water? (b) Name the principle used here. (c) What value of Tarun is reflected in this case? Answer: (d) Tarun wanted to measure the amount of water displaced by each ball when dipped in water. (b) The principle used is ‘Archimedes’ principle’. (c) Tarun showed the value of being helpful, kind and intelligent.

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NCERT Solutions for Class 9 Science Chapter 10 Gravitation

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NCERT Solutions for Class 9 Science Chapter 10 Gravitation

NCERT Solutions for Class 9 Science (physics) Chapter 10 Gravitation are given below. In these solutions, we have answered all the intext and exercise questions provided in NCERT class 9 science textbook. Class 9 NCERT Solutions Science Chapter 10 provided in this article are strictly based on the CBSE syllabus and curriculum. Students can easily download these solutions in PDF format for free from our app.

Class 9 Science Chapter 10 Textbook Questions and Answers

INTEXT QUESTION

PAGE NO 134

Question 1: State the universal law of gravitation 

Answer:   The universal law of gravitation states that every object in the universe attracts every other object with a force called the gravitational force. The force acting between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. 

For two objects of masses m 1 and m 2 and the distance between them r, the force (F) of attraction acting between them is given by the universal law of gravitation as:

Question 2: Write the formula to find the magnitude of the gravitational force between the earth and an object on the surface of the earth. 

Answer:  Let M E be the mass of the Earth and ‘m’ be the mass of an object on its surface. If R is the radius of the Earth, then according to the universal law of gravitation, the gravitational force (F) acting between the Earth and the object is given by the relation:

PAGE NO 136

Question 1: What do you mean by free fall? 

Answer: Earth’s gravity attracts each object to its center. When an object is dropped from a certain height, under the influence of gravitational force it begins to fall to the surface of Earth. Such an object movement is called free fall.

Question 2: What do you mean by acceleration due to gravity? 

Answer: When an object falls towards the ground from a height, then its velocity changes during the fall. This changing velocity produces acceleration in the object. This acceleration is known as acceleration due to gravity (g). Its value is given by 9.8 m/s 2 . 

PAGE NO 138

Question 1: What are the differences between the mass of an object and its weight? 

Question 2: Why is the weight of an object on the moon 1/6 th its weight on the earth?

PAGE NO 141

Question 1: Why is it difficult to hold a school bag having a strap made of a thin and strong string? 

Answer: It is difficult to hold a school bag having a thin strap because the pressure on the shoulders is quite large. This is because the pressure is inversely proportional to the surface area on which the force acts. The smaller is the surface area; the larger will be the pressure on the surface. In the case of a thin strap, the contact surface area is very small. Hence, the pressure exerted on the shoulder is very large. 

Question 2: What do you mean by buoyancy? 

Answer:   The upward force exerted by a liquid on an object immersed in it is known as buoyancy. When you try to immerse an object in water, then you can feel an upward force exerted on the object, which increases as you push the object deeper into water. 

Question 3: Why does an object float or sink when placed on the surface of water? 

Answer: An object float or sink when placed on the surface of water because of two reasons.

(i) If its density is greater than that of water, an object sinks in water.

(ii) If its density is less than that of water, an object floats in water.

PAGE NO 142

Question 1: You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg? 

Answer: When you weigh your body, an upward force acts on it. This upward force is the buoyant force. As a result, the body gets pushed slightly upwards, causing the weighing machine to show a reading less than the actual value. 

Question 2: You have a bag of cotton and an iron bar, each indicating a mass of 100 kg when measured on a weighing machine. In reality, one is heavier than other. Can you say which one is heavier and why? 

Answer: The bag of cotton is heavier than iron bar. This is because the surface area of the cotton bag is larger than the iron bar. Hence, more buoyant force acts on the bag than that on an iron bar. This makes the cotton bag lighter than its actual value. For this reason, the iron bar and the bag of cotton show the same mass on the weighing machine, but actually the mass of the cotton bag is more than that of the iron bar. 

Question 1: How does the force of gravitation between two objects change when the distance between them is reduced to half? 

Hence, if the distance is reduced to half, then the gravitational force becomes four times larger than the previous value.

Question 2: Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object? 

Answer: All objects fall on ground with constant acceleration, called acceleration due to gravity (in the absence of air resistances). It is constant and does not depend upon the mass of an object. Hence, heavy objects do not fall faster than light objects. 

Question 3: What is the magnitude of the gravitational force between the earth and a 1 kg object on its surface? (Mass of the earth is 6 × 10 24 kg and radius of the earth is 6.4 × 10 6 m). 

Answer:  Given, Mass of Earth, M = 6 × 10 24 kg  Mass of object, m = 1 kg  Universal gravitational constant, G = 6.7 × 10 −11 Nm 2 kg −2   Radius of the Earth, R = 6.4 × 10 6 m 

Question 4: The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth? Why? 

Answer: According to the universal law of gravitation, two objects attract each other with equal force, but in opposite directions. The Earth attracts the moon with an equal force with which the moon attracts the earth. 

Question 5: If the moon attracts the earth, why does the earth not move towards the moon? 

Answer: The Earth and the moon experience equal gravitational forces from each other. However, the mass of the Earth is much larger than the mass of the moon. Hence, it accelerates at a rate lesser than the acceleration rate of the moon towards the Earth. For this reason, the Earth does not move towards the moon. 

Question 6: What happens to the force between two objects, if

(i) the mass of one object is doubled? (ii) the distance between the objects is doubled and tripled? (iii) the masses of both objects are doubled?

Answer: According to the universal law of gravitation, the force of gravitation between two objects is given by:

Question 7: What is the importance of universal law of gravitation? 

Answer: The universal law of gravitation explains many phenomena that were believed to be unconnected:

(i) The motion of the moon round the earth (ii) The force that binds North American nation to the world (iii) The tides because of the moon and therefore the Sun (iv) The motion of planets round the Sun

Question 8: What is the acceleration of free fall?

Answer: When objects fall towards the Earth under the effect of gravitational force alone, then they are said to be in free fall. Acceleration of free fall is 9.8 ms −2 , which is constant for all objects (irrespective of their masses). 

Question 9: What do we call the gravitational force between the Earth and an object? 

Answer: Gravitational force between the earth and an object is known as the weight of the object. 

Question 10:  Amit buys few grams of gold at the poles as per the instruction of one of his friends. He hands over the same when he meets him at the equator. Will the friend agree with the weight of gold bought? If not, why? [Hint: The value of  is greater at the poles than at the equator]. 

Answer:  Weight of a body on the Earth is given by W = mg Where,   m = Mass of the body  g = Acceleration due to gravity 

The value of g is greater at poles than at the equator. Therefore, gold at the equator weighs less than at the poles. Hence, Amit’s friend will not agree with the weight of the gold bought. 

Question 11: Why will a sheet of paper fall slower than one that is crumpled into a ball?

Answer: Surface area of a Sheet which is crumpled into a ball, is much smaller than the surface area of a plain or flat sheet. Therefore, despite both experience same force of gravity, the plain or flat sheet of paper will have to face more air resistance than the crumpled ball, so it will fall slower than the sheet crumpled into a ball.

Question 13: A ball is thrown vertically upwards with a velocity of 49 m/s. Calculate:  (i)  the maximum height to which it rises.  (ii) the total time it takes to return to the surface of the earth. 

Answer: (i) According to the equation of motion under gravity v 2 − u 2 = 2gs  Where, u = Initial velocity of the ball  v = Final velocity of the ball  s = Height achieved by the ball  g = Acceleration due to gravity 

At maximum height, final velocity of the ball is zero, i.e., v = 0 m/s and u = 49 m/s

During upward motion, g = − 9.8 m s −2   Max. Height attained by the ball (s) = ?

∴ Max. Height attained by the ball (s) = 122.5 m

(ii) Let t be the time taken by the ball to reach the height 122.5 m, then according to the first equation of motion

Time for upward journey of the ball will be the same as time for downward journey i.e., t = 5 s.

Therefore, total time taken by the ball to return = 5 + 5 = 10 s 

Question 14: A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity just before touching the ground. 

Answer:  According to the equation of motion under gravity v 2 − u 2 = 2gs  Where,  u = Initial velocity of the stone = 0 m/s  v = Final velocity of the stone  s = Height of the stone = 19.6 m  g = Acceleration due to gravity = 9.8 ms −2  

Now, v 2 = u 2 + 2as ⇒ v 2 − u 2 = 2as ⇒ v 2 − 0 2 = 2 × 9.8 × 19.6  ⇒ v 2 = 2 × 9.8 × 19.6 ⇒ v 2 = 19.6 × 19.6 ⇒ v 2 = (19.6) 2 ⇒ v = 19.6 ms −1  

Hence, the velocity of the stone just before touching the ground is 19.6 ms −1 .  

Question 15: A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s 2 , find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone? 

Answer:  Given u = Initial velocity of the stone = 40 m/s  v = Final velocity of the stone = 0 m/s  s = Height of the stone   g = Acceleration due to gravity = −10 ms −2   the maximum height attained by the stone (s) = ? 

According to the equation of motion under gravity, v 2 − u 2 = 2gs 

Therefore, total distance covered by the stone during its upward and downward journey = 80 + 80 = 160 m 

Net displacement during its upward and downward journey = 80 + (−80) = 0. 

Question 16: Calculate the force of gravitation between the earth and the Sun, given that the mass of the earth = 6 × 10 24 kg and of the Sun = 2 × 10 30 kg. The average distance between the two is 1.5 × 10 11 m. 

Question 17: A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. Calculate when and where the two stones will meet. 

Answer:   Let the two stones meet after a time t. 

When the stone dropped from the tower  Initial velocity, u = 0 m/s  Let the displacement of the stone in time t from the top of the tower be s.   Acceleration due to gravity, g = 9.8 ms −2  

When the stone thrown upwards  Initial velocity, u = 25 ms −1   Let the displacement of the stone from the ground in time t be 𝑠′.   Acceleration due to gravity, g = −9.8 ms −2  

The combined displacement of both the stones at the meeting point is equal to the height of the tower 100 m. 

In 4 s, the falling stone has covered a distance given by (1) as 𝑠 = 4.9 × 4 2 = 78.4 𝑚

Therefore, the stones will meet after 4s at a height (100 – 78.4) = 20.6 m from the ground.

Question 18: A ball thrown up vertically returns to the thrower after 6 s. Find 

(a) The velocity with which it was thrown up, (b) The maximum height it reaches, and (c) Its position after 4s.

Answer: (a) The velocity with which ball was thrown up : Acceleration due to gravity, g = – 9.8 ms –2   As the total time taken in upward and return journey by the ball is 6 s. Therefore, The upward journey, t = 6/2 s = 3 s Final velocity, v = 0 ms –1 Initial velocity, u = ?

Using equation of motion, v = u + at, we have 

0 = u + (−9.8 × 3)  ⇒ u = 9.8 × 3 ⇒ u = 29.4 m/s 

Hence, the ball was thrown upwards with a velocity of 29.4 m/s. 

(b) Let the maximum height attained by the ball be s.  Initial velocity during the upward journey, u = 29.4 m/s  Final velocity, v = 0 m/s Acceleration due to gravity, g = −9.8 ms −2  

Hence, the maximum height is 44.1 m.

(c) Ball attains the maximum height after 3s. After attaining this height, it will start falling downwards.  

In this case, 

Initial velocity, u = 0 m/s

Position of the ball after 4 s of the throw is given by the distance travelled by it during its downward journey in 4 s − 3 s = 1 s. 

Now, total height = 44.1 m 

This means, the ball is 39.2 m (44.1 m − 4.9 m) above the ground after 4 seconds. 

Question 19: In what direction does the buoyant force on an object immersed in a liquid act? 

Answer: An object immersed in a liquid experiences buoyant force in the upward direction. 

Question 20: Why does a block of plastic released under water come up to the surface of water? 

Answer: Two forces act on an object immersed in water. One is the gravitational force, which pulls the object downwards, and the other is the buoyant force, which pushes the object upwards. If the upward buoyant force is greater than the downward gravitational force, then the object comes up to the surface of the water as soon as it is released within water. Due to this reason, a block of plastic released under water comes up to the surface of the water. 

Question 21: The volume of 50 g of a substance is 20 cm 3 . If the density of water is 1 g cm −3 , will the substance float or sink? 

Answer: If the density of an object is more than the density of a liquid, then it sinks in the liquid. On the other hand, if the density of an object is less than the density of a liquid, then it floats on the surface of the liquid. 

The density of the substance is more than the density of water (1 g cm −3 ).  Hence, the substance will sink in water. 

Question 22: The volume of a 500 g sealed packet is 350 cm 3 . Will the packet float or sink in water if the density of water is 1 g cm −3 ? What will be the mass of the water displaced by this packet? 

Answer: Density of the 500 g sealed packet

The density of the substance is more than the density of water (1𝑔/𝑐𝑚 3 ). Hence, it will sink in water. 

The mass of water displaced by the packet is equal to the volume of the packet, i.e., 350g. 

Class 9 Science NCERT Solutions Chapter 10 Gravitation

CBSE Class 9 Science NCERT Solutions Chapter 10 helps students to clear their doubts and to score good marks in the board exam. All the questions are solved by experts with a detailed explanation that will help students complete their assignments & homework. Having a good grasp over CBSE NCERT Solutions for Class 9 Science will further help the students in their preparation for board exams and other competitive exams such as NTSE, Olympiad, etc.

NCERT Solutions for Class 9 Science Chapter 10 PDF

Below we have listed the topics discussed in NCERT Solutions for Class 9 Science Chapter 10. The list gives you a quick look at the different topics and subtopics of this chapter.

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NCERT Solutions for Class 9 Science Chapter 10 Gravitation

• Last modified on: 3 years ago
• Reading Time: 28 Minutes

Here we have given NCERT Solutions for Class 9 Science Chapter 10 Gravitation.

INTEXT Questions

Question 1. State the universal law of gravitation. Solution: According to universal law of gravitation, every particle in the universe attracts every other particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of distance between them. The direction of force is along the line joining the two particles.

Question 3. What do you mean by free fall? Solution: All objects falling towards earth under the action of gravitational force of earth alone are said to be in free fall.

Question 4. What do you mean by acceleration due to gravity? Solution: The acceleration with which an object fall freely towards the earth is known as acceleration due to gravity. It is denoted by g and its value is 9.8 m s -2 .

Question 5. What are the differences between the mass of an object and its weight? Solution:

Question 8. What do you mean by buoyancy? Solution: Whenever an object is immersed in a liquid, either partially or fully, an upward force is exerted on the object by the liquid. This upward force is called upthrust or buoyant force or force of buoyancy and the property of the fluid due to which this upthrust is exerted on the object is called buoyancy.

Question 9. Why does an object float or sink when placed on the surface of water? Solution: When the object has density less than 1 g cm -3  (density of water), then it floats on the surface of water, because, it always displaces more weight of water than its own weight. As buoyant force is more than its own weight, therefore, it floats. When the object has density more than 1 g cm-3, then it sinks in water, because it always displaces less weight of water than its own weight. As buoyant force is less than its own weight, therefore, it sinks.

Question 10. You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg? Solution: A weighing machine is a sort of spring balance which measure the weight and not the mass of a body. When we stand on the weighing machine, our weight which is due to gravitational attraction of the earth acts vertically downwards. But the buoyancy due to air on our body acts vertically upwards. As a result of this, our apparent weight true weight – buoyant force is less than the true weight. Since the weighing machine measures the apparent weight, our true weight is more, i.e., more than 42 kg.

Question 11. You have a bag of cotton and an iron bar, each indicating a mass of 100 kg when measured on a weighing machine. In reality, one is heavier than other. Can you say which one is heavier and why? Solution: We know that true weight = apparent weight + upthrust. The cotton bag is heavier than the iron bar. This is due to the reason, that the bag of cotton which has more volume (as it has less density) than the iron bar (which has more density), experiences more upthrust due to air.

NCERT Exercises

Question 5. If the moon attracts the earth, why does the earth not move towards the, moon? Solution: Both the earth and the moon attract each other with the same force. But according to Newton’s second law of motion, acceleration produced in a body by any force is inversely proportional to the mass of the body. Since, mass of the earth is much more than that of the moon, the acceleration produced in the earth is negligible. As a result, it appears as if the earth does not move towards the moon.

Question 7. What is the importance of universal law of gravitation? Solution: Universal law of gravitation is important as it accounts, (a) for the existence of the solar system, i.e., motion of planets around the sun. (b) for holding the atmosphere near the surface of the earth. (c) for the flow of water in rivers. (d) for rainfall and snowfall. (e) for occurrence of tides.

Question 8. What is the acceleration of free fall? Solution: All objects moving towards earth on account of gravitational force of earth on them are said to be in free fall. This force produces a uniform acceleration in the object. This is acceleration of free fall and its value is 9.8 m s -2 .

Question 9. What do we call the gravitational force between the earth and an object? Solution: The gravitational force between the earth and an object is called the force of gravity or simply earth’s gravity.

Question 10. Amit buys few grams of gold at the poles as per the instruction of one of his friends. He hands over the same when he meets him at the equator. Will the friend agree with the weight of gold bought? If not, why? Solution: We know that the value of g is greater at the poles than at the equator. So the weight of gold at the equator will be less than the weight of gold at the poles. So it is obvious that the friend at equator will not agree with the weight of gold bought at poles.

Question 11. Why will a sheet of paper fall slower than one that is crumpled into a ball? Solution: A sheet of paper will fall slower than the one that is crumpled into a ball. This is because the air offers resistance due to friction to the motion of the falling objects. The resistance offered by air to the sheet of paper is more than the resistance offered by air to the paper ball because the sheet has larger area.

Question 13. A ball is thrown vertically upwards with a velocity of 49 m/s. Calculate (i) the maximum height to which it rises, (ii) the total time it takes to return to the surface of the earth. Solution:

Question 14. A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity just before touching the ground. Solution: Question 15. A stone is- thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s -2 , find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone? Solution: As final position of the stone coincides with its initial position, net displacement = 0 Total distance covered by the stone = h + h = 80m + 80m = 160 m

Question 16. Calculate the force of gravitation between the earth and the sun, given that the mass of the earth = 6 × 10 24  kg and of the sun = 2 × 10 30  kg. The average distance between the two is 1.5 × 10 11  m. Solution: Thus, the earth and the sun attract each other by a gravitational force of 3.56 × 10 22  N.

Question 20. Why does a block of plastic released under water come up to the surface of water? Solution: The buoyant force acting on the block of plastic is more than its weight. As a result of this, it comes up when released under water.

The cause of this larger buoyant force on the block of plastic is due to its density being lesser than that of water.

Question 21. The volume of 50 g of a substance is 20 cm 3 . If the density of water is 1 g cm -3 , will the substance float or sink? Solution: As the density of the substance is greater than that of water, the given substance will sink in water.,

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NCERT Solutions for Class 9 Science Chapter 10 Gravitation PDF

NCERT Solutions is very important for all the students who want to ace their examinations. These solutions are developed by highly qualified subject matter experts at Selfstudys who have devoted their time and energy to help the students understand the topic with a clearly understanding. They have made sure to include each and every topic in these solutions and that too with explanations. Apart from this, these NCERT Solutions for Class 9 Science Chapter 10 Gravitation are created as per the latest curriculum of CBSE (Central Board of Secondary Education) which also ensures that the students will be updated about the latest syllabus. This will increase their chances of scoring good marks in the exams. 

Our subject matter experts have covered each and every topic in these NCERT Solutions for Class 9 Science Chapter 10 Gravitation. These solutions break the hard topics into easy terms which makes it easier for all the students to understand and learn the concept in an effective manner. Studying these solutions will give the students an idea about all the types of questions, from easy to intermediate to advanced. Also, the students will get to know about the most common types of questions that have a higher chance of appearing in the exam. 

This NCERT Solutions for class 9 Science Chapter 10 Gravitation is written in simple language as our subject matter experts are aware of the learning power of each and every student, this is why they have created these solutions in a simple language so that no student faces any difficulty in studying from them. These NCERT Solutions for Class 9 Science Chapter 10 Gravitation can be easily downloaded from the website of Selfstudys. 

NCERT Solutions for Class 9 Science Chapter 10 Gravitation PDF 

The NCERT Solutions for Class 9 Science Chapter 10 Gravitation can be easily downloaded from the website of Selfstudys. As they are developed by the subject matter experts in PDF Format, it becomes easier for the students to access them. Students can also access them on their mobile phones and can share them. 

NCERT Solutions for Class 9 Science Exercise Wise 

The subject matter experts at Selfstudys have created the NCERT Solutions for Class 9 in a chapter-wise format which helps the students to study the concepts in an organized way. This prevents them from getting confused and gives them a clear understanding of all the topics. 

NCERT Solutions for Class 9 Science Formula Wise 

NCERT Solutions for Class 9 Science Formula Wise consists of accurate formulas for topics covered in Science Class 9. These formulas act as a quick reference guide for students, helping them understand and apply scientific concepts effectively in exams and problem-solving situations. 

How to Download the NCERT Solutions for Class 9 Science Chapter 10 Gravitation? 

Downloading the NCERT Solutions for Class 9 Science Chapter 10 Gravitation is if you know the right steps. The steps to download them are as follows: 

• Visit the official website of Selfstudys i.e. Selfstudys.com.

• Once the website is completely loaded, you need to click on the three lines which you will find on the upper left side. Following that, you have to click on the ‘NCERT Books and Solutions’ column. 

• After clicking on the option of ‘NCERT Books and Solutions’, a new list will open where you need to select the option of ‘NCERT Solutions’. 

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• In this case, you need to select class 9 and the subject Science to download the NCERT Solutions for Class 9 Science Chapter 10 Gravitation. 

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The NCERT Solutions for Class 9 Science Chapter 10 Gravitation has several benefits to offer to the students. Some of the most important of them are: 

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• Boosts Various Skills: Regularly practicing the NCERT Solutions for Class 9 Science Chapter 10 Gravitation helps the students to boost various skills of the students which consist of various skills like problem-solving skills and analytical skills. 
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There are various tips that can help the students to study effectively from the NCERT Solutions for Class 9 Science Chapter 10 Gravitation: 

• Do a thorough reading of the NCERT Solutions: All the students are advised to do a thorough reading of the NCERT Solutions for Class 9 Science Chapter 10 Gravitation as it will help them to understand the basic concepts with clearly understanding. 
• Create a timetable and follow it: It is very important for all the students to not only create a timetable but also follow it on a regular basis as it will help the students to know about the importance of discipline and getting disciplined. The students are advised to give at least 30-40 minutes to learn the concepts thoroughly. They should give enough time to each topic that is present in the NCERT Solutions for Class 9 Science Chapter 10 Gravitation. Regularly following this schedule ensures the timely completion of the topics. 
• Reduce the distractions: It is advisable for all the students to reduce all teh distractions as they can affect their exam preparation of the student. They should stay away from their mobile phones and other electronic gadgets, for example, TV, etc. to avoid all the distractions while studying NCERT Solutions for Class 9 Science Chapter 10 Gravitation. 

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• Practice these NCERT Solutions on a regular basis: All the students are advised to regularly practice the NCERT Solutions for Class 9 Science Chapter 10 Gravitation as it will help them to grasp the concepts easily which will eventually enable them to score good marks in their exams. Apart from this, the conceptual knowledge of all the students is also increased. 
• Make a list of your mistakes and work on them: All the students are advised to make a list of their mistakes while studying the NCERT Solutions for Class 9 Science Chapter 10 Gravitation and work on them as it will help them to understand where they are lacking behind and what they can do to improve themselves in order to do well in their exams. 
• Practice additional exercises: Apart from the exercises provided in the NCERT Solutions for Class 9 Science Chapter 10 Gravitation, the students should practice additional problems related to the concepts covered in Chapter 10 Gravitation. This will further reinforce your understanding and help you apply the learned concepts in different contexts. 

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To maximize your learning potential while solving the NCERT Solutions for Class 9 Science Chapter 10 Gravitation, here are the tips which can help you: 

• Read the NCERT Solutions thoroughly: It is advisable for all the students to read the NCERT Solutions for Class 9 Science Chapter 10 Gravitation thoroughly as it will help them to understand the topics clearly understanding which will make it easier for them to learn all the concepts. 
• Practice on a regular basis: This is one of the most important features which every student should follow in order to do exam preparation effectively. This means practicing the NCERT Solutions on a regular basis as it will help them in understanding the concepts with clear understanding and in-depth knowledge which can help them to score good marks in the exams. 
• Revise the concepts on a regular basis: Revising all the concepts from NCERT Solutions for Class 9 Science Chapter 10 Gravitation is very important for students as it helps them recall all the information they studied during exam preparation. To ensure regular revision, students can use various methods such as creating flashcards, notes, and other study materials. 

What Are the Methods To Study From NCERT Solutions for Class 9 Science Chapter 10 Gravitation? 

Studying for the exam requires focus and concentration. below we will discuss various methods of how students can study for an exam with the help of ncert solutions for class 9 science chapter 10 gravitation: .

• Making a strong grip on basics: Developing a strong foundation in the fundamentals is crucial for all students, and studying NCERT Solutions for Class 9 Science Chapter 10 Gravitation is an important step towards achieving this goal. By mastering the basic concepts, students can gain a clear understanding of the subject, which in turn facilitates quicker and more effective learning. 
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• Always read the summary of your textbook: All the students are advised to read the summary which is included in the NCERT Solutions for Class 9 Science Chapter 10 Gravitation. The students should read them regularly as they will get benefited because they will get in-depth knowledge of all the topics and will also help them to prepare well for the exams. This will increase their chances of scoring good marks in the exams. 
• Find your strengths and weaknesses: It is very essential for all the students to identify their strengths and weaknesses as it will help them to understand where they need to do more hard work in order to score good marks in their examinations. 
• Do revision on a timely basis: If students want to score good marks in their exams, it is very important for them to engage in the timely revision of NCERT Solutions for Class 9 Science Chapter 10 Gravitation. 

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NCERT Solutions for Class 9 Science Chapter 9- Gravitation

• NCERT Solutions
• Chapter 10 Gravitation

NCERT Solutions for Gravitation Class 9 Questions and Answers FREE PDF Download

Class 9 Science Ch 9 explores the concept of gravitational force, understanding its effects on celestial bodies like planets and moons, and Archimedes’ Principle. Vedantu’s Class 9 Gravitation NCERT Solutions solves all the questions in the chapter and helps students navigate through complex concepts with clarity and precision.  Access Vedantu's Gravitation Class 9 solutions for step-by-step explanations and problem-solving strategies and enhance your learning experience.

Download Vedantu's Science Class 9 Gravitation NCERT Solutions, revised to align with the Class 9 Science syllabus . Start your academic journey with Vedantu and pave your way towards academic excellence.

Quick Insights for NCERT Solutions for Class 9 Chapter 9 Science Gravitation

Class 9 Science Ch 9 comprehends the concept of gravitation, the force of attraction that exists between any two objects with mass, and elucidates Newton's Law of Universal Gravitation, a cornerstone of classical physics. 

Ch 9 Science Class 9 explores the effects of gravitation in maintaining the stability of celestial bodies such as planets, stars, and galaxies.

Class 9 Gravitation Question Answer delves into the concept of acceleration due to gravity, the distinction between weight and mass, and Archimedes’ Principle.

Gravitation Class 9 Questions And Answers develop proficiency in solving numerical problems related to the motion of objects under the influence of the earth's gravitational force, Pressure, and Thrust.

Vedantu offers additional resources such as class notes, important concepts, formulas, and exemplar solutions to reinforce learning and ensure a strong grasp of foundational scientific principles.

Access NCERT Solutions For Class 9 Science Chapter 9 – Gravitation

Intext exercise 1.

1. State the universal law of gravitation.

Ans: Every object in the universe attracts every other object with some force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. The force acts along the line joining the centres of two objects.

Let the two objects \[A\] and \[B\]of masses \[M\]and \[m\] lie at a distance \[d\] from each other. Let the force of attraction between two objects be \[F\].

\[F=\frac{GMm}{{{r}^{2}}}\]

Where, 

\[G\]is the universal gravitation constant which is given by:

\[G=6.67\times {{10}^{-11}}N{{m}^{2}}k{{g}^{-2}}\]

2. Write the formula to find the magnitude of the gravitational force between the earth and an object on the surface of the earth.

Ans: Let the mass of the Earth be \[M\] and the mass of an object on its surface be \[m\]. If \[R\]is the radius of the Earth, then according to the universal law of gravitation, the gravitational force (\[F\]) that acts between the Earth and the object can be given by the relation:

\[F=\frac{GMm}{{{R}^{2}}}\].

Intext Exercise 2

1. What do you mean by free fall?

Ans: Each object is drawn towards the centre of the Earth by its gravity. When any object is released from a certain height, under the impact of gravitational force, it falls to the Earth's surface. The movement of the object is said to be in free fall.

2. What do you mean by acceleration due to gravity?

Ans: When any object falls freely from a certain height towards the earth's surface, its velocity changes with respect to time. This change in velocity causes acceleration. This acceleration is known as the acceleration due to gravity (\[g\]). The value of acceleration due to gravity is \[9.8m{{s}^{-2}}\].

Intext Exercise 3

1. What are the differences between the mass of an object and its weight?

Ans: The difference between the mass of an object and its weight is given in the table below:

2. Why is the weight of an object on the moon \[\frac{1}{6}th\] its weight on the earth?

Ans: Let the mass of the Earth be \[{{M}_{E}}\] and the mass of an object on the surface of earth \[=m\] and the radius of earth \[{{R}_{E}}\].

According to the Universal law of gravitation, weight \[{{W}_{E}}\] of the object on the surface of the earth is given by,

\[{{W}_{E}}=\frac{G{{M}_{E}}m}{{{R}_{E}}^{2}}\]

Let \[{{M}_{M}}\] and \[{{R}_{M}}\] be the mass and radius of the moon. Then, according to the universal law of gravitation, weight \[{{W}_{M}}\] of the object on the surface of the moon is given by:

\[{{W}_{M}}=\frac{G{{M}_{M}}m}{{{R}_{M}}^{2}}\]

So, ratio of weight of object on moon to weight on earth is

\[\frac{{{W}_{M}}}{{{W}_{E}}}=\frac{{{M}_{M}}{{R}_{E}}^{2}}{{{M}_{E}}{{R}_{M}}^{2}}\]

Where, \[{{M}_{E}}=5.98\times {{10}^{24}}kg\] 

\[{{M}_{M}}=7.36\times {{10}^{22}}kg\]

\[{{R}_{E}}=6.4\times {{10}^{6}}m\]

\[{{R}_{M}}=1.74\times {{10}^{6}}m\] 

Substituting the values in the ratio,

\[\Rightarrow \frac{{{W}_{M}}}{{{W}_{E}}}=\frac{7.36\times {{10}^{22}}\times {{\left( 6.37\times {{10}^{6}} \right)}^{2}}}{5.98\times {{10}^{24}}\times {{\left( 1.74\times {{10}^{6}} \right)}^{2}}}\]

\[\Rightarrow \frac{{{W}_{M}}}{{{W}_{E}}}=0.165\approx \frac{1}{6}\]

Hence, the weight of an object on the moon is \[\frac{1}{6}th\] of its weight on the Earth.

Intext Exercise 4

1. Why is it difficult to hold a school bag with a strap made of a thin and strong string?

Ans: Pressure can be given by the formula,

\[P=\frac{F}{A}\]

Pressure is inversely proportional to the surface area on which the force is acting. The smaller is the surface area, the larger will be the pressure on the surface on which the force is being acted upon. In the case of a thin strap of the school bag, the contact surface area is very less. Hence, the pressure exerted on the shoulder is very high. Therefore, it becomes difficult to hold a school bag with a thin strap.

2. What do you mean by buoyancy?

Ans: The liquid exerts an upward force on any object when it is immersed in a liquid or fluid. The tendency of the liquid to exert such an upward force on the object is called buoyancy, and the upward force which is exerted on the object by the liquid is called the buoyant force.

3. Why does an object float or sink when placed on the surface of the water?

Ans: If the density of an object is greater than the density of the liquid, it will sink into the liquid. This is due to the buoyant force which is acted by the object is less than the force of gravity. 

On the contrary, if the density of the object is less than the density of the liquid, it floats on the liquid's surface. This is because the force that is acting on the object is greater than the force of gravity.

Intext Exercise 5

1. You find your mass to be \[42\] kg on a weighing machine. Is your mass more or less than \[42\]kg?

Ans: An upward force acts on our body when we weigh our body while standing on a weighing machine. The buoyant force is which is a upward force that is acting. Consequently, the body is pushed up slightly, resulting in the weighing machine showing less reading than the real value.

2. You have a bag of cotton and an iron bar, each indicating a mass of \[100kg\] when measured on a weighing machine. In reality, one is heavier than other. Can you say which one is heavier and why?

Ans: Weight measured \[=\] Actual weight \[-\] buoyant force

Therefore, Actual weight \[=\] Weight measured \[+\]buoyant force

As the surface area of the cotton, the bag is greater than the iron bar, more buoyant force acts on the bag than that on the iron bar. Hence, the mass of the cotton bag is more than that of the iron bar.

NCERT Exercise

1. How does the force of gravitation between two objects change when the distance between them is reduced to half?

Ans: According to the universal law of gravitation, the gravitational force (\[F\]) acting between two objects of mass \[{{m}_{1}}\]and \[{{m}_{2}}\], separated by a distance ‘\[r\]’ is given by

\[F=\frac{G{{m}_{1}}{{m}_{2}}}{{{r}^{2}}}\]

Where \[{{m}_{1}}\]and \[{{m}_{2}}\]are the masses of two bodies and \[r\]is the distance between them, \[G\] is the universal gravitational constant.

When the distance is reduced to half, i.e., \[{r}'=\frac{r}{2}\]

\[\Rightarrow F=\frac{G{{m}_{1}}{{m}_{2}}}{{{\left( \frac{r}{2} \right)}^{2}}}\]

\[\Rightarrow F=\frac{G{{m}_{1}}{{m}_{2}}}{\frac{{{r}^{2}}}{4}}\]

\[\Rightarrow F=\frac{4G{{m}_{1}}{{m}_{2}}}{{{r}^{2}}}\]

Hence, if the distance is reduced to half, then the gravitational force becomes four times that of the previous value.

2. Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object?

Ans: All the objects fall towards the ground with constant acceleration, called acceleration due to gravity (if there is no air resistance present). It is constant and independent of the mass of the object. Hence, heavy objects do not fall faster than light objects.

3. What is the magnitude of the gravitational force between the earth and a \[1kg\]object on its surface? (Mass of the earth is \[6\times {{10}^{24}}kg\] and radius of the earth is \[6.4\times {{10}^{6}}m\]).

Ans: According to the Universal law of gravitation, the gravitational force exerted on an object of mass \[m\]is given by:

Mass of Earth, \[M=6\times {{10}^{24}}kg\]

Mass of object, \[m=1kg\]

Universal gravitational constant, \[G=6.7\times {{10}^{-11}}N{{m}^{2}}k{{g}^{-2}}\]

Since the object is on the surface of the Earth, \[r=\]radius of the Earth (\[R\])

\[r=R=6.4\times {{10}^{6}}m\]

Gravitational force,

\[\Rightarrow F=\frac{6.7\times {{10}^{-11}}\times 6\times {{10}^{24}}\times 1}{{{\left( 6.4\times {{10}^{6}} \right)}^{2}}}=9.8N\].

The magnitude of the gravitational force between the earth and a \[1kg\]object on its surface is \[9.8N\].

4. The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth? Why?

Ans: According to the Universal law of gravitation, two objects attract each other and according to Newton's third law of motion, the force of attraction between two objects is the same but acts in the opposite direction. Thus, the earth attracts the moon with the same force as the moon exerts on earth but the force acts in the opposite direction.

5. If the moon attracts the earth, why does the earth not move towards the moon?

Ans: The Earth and the moon experience equal gravitational forces acting towards each other.

By Newton's Second Law, \[F=ma\]

\[\Rightarrow a=\frac{F}{m}\]

For a certain force, acceleration is inversely proportional to the mass of an object.

\[a\propto \frac{F}{m}\]

Mass of the Earth \[>>\] Mass of the moon.

Hence, the acceleration experienced by earth due to the gravitational pull of the moon is very small when compared to that experienced by the moon due to earth. That is why the Earth does not move towards the moon.

6. What happens to the force between two objects, if

a) The mass of one object is doubled?

Ans: According to the universal law of gravitation, the force of gravitation between two objects is given by: \[F=\frac{GMm}{{{r}^{2}}}\]

\[F\]is directly proportional to the product of masses of the two objects.

\[F\propto Mm\]

If the mass of one object is doubled, then the gravitational force will also change to double the original.

b) The distance between the objects is doubled and tripled?

Ans: \[F\]is inversely proportional to the square of the distance between the objects.

If the distance between the objects is doubled, then the gravitational force becomes one-fourth of its original value. Also, if the distance is tripled, then the gravitational force becomes one-ninth of its original value.

c) The masses of both objects are doubled?

Ans: \[F\]is directly proportional to the product of masses of the objects.

If the masses of both the objects are doubled, then the gravitational force becomes four times the original value.

7. What is the importance of the universal law of gravitation?

Ans: The universal law of gravitation states that every object in the universe attracts every other object.

The force of gravitation binds us to the earth.

It is the cause for the motion of the moon around the earth and planets around the sun.

It results in the formation of tides due to the moon and the Sun. High tide occurs at the side where the moon pulls towards itself.

8. What is the acceleration of free fall?

Ans: A free-falling object is an object that is falling due to gravity without any air resistance. When it falls, there is a variation in velocity with respect to time that is associated with it.

Acceleration of free fall is denoted by \[g\]and its value on the surface of the earth is \[9.8m{{s}^{-2}}\], which is constant for all objects (irrespective of their masses).

9. What do we call the gravitational force between the Earth and an object?

Ans: The gravitational force between the earth and an object is called the weight of that object. It is equal to the product of acceleration due to the gravity and mass of the object.

10. Amit buys a few grams of gold at the poles as per the instruction of one of his friends. He hands over the same when he meets him at the equator. Will the friend agree with the weight of gold bought? If not, why? (Hint: The value of g is greater at the poles than at the equator).

Ans: Weight of a body on the Earth is given by:

\[m=\]Mass of the body

\[g=\]Acceleration due to gravity

The shape of Earth is not a perfect sphere. As the radius of the earth increases from the poles to the equator, the value of \[g\]becomes greater at the poles than at the equator. Since the value of \[g\] is greater at the poles than the equator.

Therefore, gold at the equator weighs less than at the poles. Hence, Amit’s friend will not agree with the weight of the gold bought.

11. Why will a sheet of paper fall slower than one that is crumpled into a ball?

Ans: When a sheet of paper is crumbled into a ball, then its surface area becomes much lesser than the surface area of a plain non-crumpled sheet of paper.

Hence, the upward force exerted by air on the sheet is greater as compared to the one exerted on the ball. Hence the sheet falls slower as compared to a paper ball.

12.Gravitational force on the surface of the moon is only \[\frac{1}{6}\] as strong as the gravitational force on the Earth. What is the weight in newtons of a \[10kg\]object on the moon and on the Earth?

Ans: It is provided that, \[Weight\text{ }of\text{ }an\text{ }object\text{ }on\text{ }the\text{ }moon=\frac{1}{6}\times Weight\text{ }of\text{ }an\text{ }object\text{ }on\text{ }the\text{ }Earth\]

\[Weight=\,Mass\times Acceleration\]

Acceleration due to gravity, \[g=9.8m{{s}^{-2}}\]

Therefore, the weight of a 10 kg object on the Earth \[=10\times 9.8N=98N\]

Weight of the same object on the moon \[=\frac{1}{6}\times 9.8N=16.3N\]

13. A ball is thrown vertically upwards with a velocity of \[49m{{s}^{-1}}\]. Calculate

a) The maximum height to which it rises.

Ans: According to the equation of motion under gravity:

\[{{v}^{2}}-{{u}^{2}}=2gh\]

\[u=\]Initial velocity of the ball

\[v=\]Final velocity of the ball

\[h=\]Height achieved by the ball

At maximum height, final velocity of the ball is zero, i.e., \[v=0\]

\[u=49m{{s}^{-1}}\]

During upward motion, \[g=9.8m{{s}^{-2}}\]

Let \[h\] be the maximum height attained by the ball.

\[\Rightarrow {{\left( 0 \right)}^{2}}-{{\left( 49 \right)}^{2}}=2\times \left( -9.8 \right)\times h\]

\[\Rightarrow h=\frac{49\times 49}{2\times 9.8}=122.5\]

b) The total time it takes to return to the surface of the earth.

Ans: Let \[t\] be the time taken by the ball to reach the height \[122.5m\], then according to the equation of motion:

Substituting the values and solving,

\[\Rightarrow 0=49+t\times \left( -9.8 \right)\]

\[\Rightarrow 9.8t=49\]

\[\Rightarrow t=\frac{49}{9.8}=5s\]

Time of ascent = Time of descent

Therefore, the total time taken by the ball to return is \[5+5=10s\].

14. A stone is released from the top of a tower of height \[19.6m\]. Calculate its final velocity just before touching the ground.

\[u=\]Initial velocity of the stone \[=0\]

\[v=\]Final velocity of the stone

\[s=\]Height of the stone \[=9.6m\]

g = Acceleration due to gravity \[=9.8m{{s}^{-2}}\]

\[\Rightarrow {{v}^{2}}-{{0}^{2}}=2\times 9.8\times 19.6\]2

\[\Rightarrow {{v}^{2}}=2\times 9.8\times 19.6={{\left( 19.6 \right)}^{2}}\]

\[\Rightarrow v=19.6m{{s}^{-1}}\]

Hence, the velocity of the stone just before touching the ground is \[19.6m{{s}^{-1}}\].

15. A stone is thrown vertically upward with an initial velocity of \[40m{{s}^{-1}}\]. Taking \[g=10m{{s}^{-2}}\], find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?

\[u=\]Initial velocity of the stone \[=40m{{s}^{-1}}\]

\[v=\]Final velocity of the stone\[=0\]

\[s=\]Height of the stone 

g = Acceleration due to gravity \[=-10m{{s}^{-2}}\]

Let \[h\] be the maximum height attained by the stone.

\[\Rightarrow 0-{{\left( 40 \right)}^{2}}=2\times h\times \left( -10 \right)\]

\[\Rightarrow h=\frac{40\times 40}{20}=80m\]

Therefore, the total distance covered by the stone during its upward and downward journey is \[80+80=160m\].

The net displacement of the stone during its upward and downward

journey is \[80+\left( -80 \right)=0m\].

16. Calculate the force of gravitation between the earth and the Sun, given that the mass of the earth \[=6\times {{10}^{24}}kg\] and of the Sun \[=2\times {{10}^{30}}kg\]. The average distance between the two is \[1.5\times {{10}^{11}}m\].

Ans: According to the Universal l law of gravitation, the force of attraction between the Earth and the Sun is given by:

\[{{M}_{Sun}}=\]Mass of the Sun \[=2\times {{10}^{30}}kg\]

\[{{M}_{Earth}}=\]Mass of the Earth \[=6\times {{10}^{24}}kg\]

\[R=\] Average distance between the Earth and the Sun \[=1.5\times {{10}^{11}}m\]

\[G=\]Universal gravitational constant \[=6.7\times {{10}^{-11}}N{{m}^{2}}k{{g}^{-2}}\].

\[F=\frac{G{{M}_{Sun}}{{M}_{Earth}}}{{{R}^{2}}}\]

\[\Rightarrow F=\frac{6.7\times {{10}^{-11}}\times 2\times {{10}^{30}}\times 6\times {{10}^{24}}}{{{\left( 1.5\times {{10}^{11}} \right)}^{2}}}\]

\[\Rightarrow F=3.57\times {{10}^{22}}N\]

Hence, the force of gravitation between the earth and the sun is \[3.57\times {{10}^{22}}N\].

17. A stone is allowed to fall from the top of a tower \[100m\] high and at the same time another stone is projected vertically upwards from the ground with a velocity of \[25m{{s}^{-1}}\]. Calculate when and where the two stones will meet.

Ans: Let the two stones meet after time \[t\]from the start.

a) For the stone dropped from the tower:

Initial velocity, \[u=0\].

Let the displacement of the stone in time t from the top of the tower be s.

From the equation of motion,

\[s=ut+\frac{1}{2}g{{t}^{2}}\]

\[\Rightarrow s=0\times t+\frac{1}{2}\times 9.8\times {{t}^{2}}\]

\[\Rightarrow s=4.9{{t}^{2}}\]……. (1)

b) For the stone thrown upwards:

Initial velocity, \[u=25m{{s}^{-1}}\]

Let the displacement of the stone from the ground in time \[t\]be \[{s}'\].

Equation of motion,

\[{s}'=ut+\frac{1}{2}g{{t}^{2}}\]

\[\Rightarrow {s}'=25t-\frac{1}{2}\times 9.8\times {{t}^{2}}\]

\[\Rightarrow {s}'=25t-4.9{{t}^{2}}\]…… (2)

The combined displacement of both the stones at the meeting point is equal to the height of the tower \[100\]m.

\[s+{s}'=100\]…… (3)

Substituting equation (1) and (2) in (3),

\[4.9{{t}^{2}}+25t-4.9{{t}^{2}}=100\]

\[\Rightarrow 25t=100\]

\[\Rightarrow t=\frac{100}{25}=4s\]

In \[4s\], the falling stone has covered a distance given by equation (1) as

\[s=\frac{1}{2}\times 9.8\times {{4}^{2}}=78.4m\]

Therefore, the stones will meet after \[4s\] at a height \[\left( 100-78.4 \right)=21.6m\] from the ground.

18. A ball thrown up vertically returns to the thrower after \[6s\]. Find

a) The velocity with which it was thrown up,

Ans: Time of ascent is equal to the time of descent. The ball takes a total of \[6s\]for its upward and downward journey.

Hence, time taken for upward journey, \[t=\frac{6}{2}=3s\]

Final velocity of the ball at the maximum height, \[v=0\]

Equation of motion, \[v=u+gt\]will give,

\[\Rightarrow 0=u+\left( -9.8\times 3 \right)\]

\[\Rightarrow u=9.8\times 3=29.4m{{s}^{-1}}\]

Hence, the ball was thrown upwards with a velocity of \[29.4m{{s}^{-1}}\].

b) The maximum height it reaches 

Ans: Let the maximum height attained by the ball be \[h\].

Initial velocity during the upward journey, \[u=29.4m{{s}^{-1}}\] 

Final velocity, \[v=0\]

Acceleration due to gravity, \[g=-9.8m{{s}^{-2}}\]

\[s=ut+\frac{1}{2}a{{t}^{2}}\]

\[h=29.4\times 3+\frac{1}{2}\times \left( -9.8 \right)\times {{\left( 3 \right)}^{2}}=44.1m\] 

c) Its position after \[4s\].

Ans: Ball attains the maximum height after \[3s\]. After attaining this height, it will start falling downwards.

In this case, Initial velocity, \[u=0\]

Position of the ball after \[4s\] of the throw is given by the distance

travelled by it during its downward journey in \[4s-3s=1s\]

\[s=0\times t+\frac{1}{2}\times 9.8\times {{1}^{2}}=4.9m\]

Total height \[=44.1m\]

This means that the ball is \[44.1m-4.9m=39.2m\] above the ground

after \[4\]seconds.

19. In what direction does the buoyant force on an object immersed in a liquid act?

Ans: An object immersed in a liquid is acted upon by the buoyant force in the vertically upward direction.

20. Why does a block of plastic released under water come up to the surface of water?

Ans: The number of forces acting on a certain item in water are two. The first one is the gravitational force pulling down the object, and the other is the buoyant force pushing up the object. If the buoyant force acting in the upward direction is higher than the gravitational force that is acting downward, then the object goes up to the water's surface as quickly as it is released into water. That is why a block of plastic released under the water comes up to the surface of the water.

21. The volume of \[50g\]of a substance is \[20c{{m}^{3}}\] . If the density of water is \[1gc{{m}^{-3}}\], will the substance float or sink?

Ans: If the density of an object is more than the density of a liquid, then it sinks in the liquid. If the density of an object is less than the density of a liquid, then it floats

\[Density\text{ }of\text{ }the\text{ }substance=\frac{Mass\text{ }of\text{ }the\text{ }substance}{Volume\text{ }of\text{ }the\text{ }substance}\]

\[\Rightarrow Density\text{ }of\text{ }the\text{ }substance=\frac{50}{20}\]

\[\Rightarrow Density\text{ }of\text{ }the\text{ }substance=2.5gc{{m}^{-3}}\].

The density of the substance \[>\] The density of water \[\left( 1gc{{m}^{-3}} \right)\].

Hence, the substance will sink in water.     

22. The volume of a \[500g\] sealed packet is \[350c{{m}^{3}}\]. Will the packet float or sink in water if the density of water is \[1gc{{m}^{-3}}\]? What will be the volume of the water displaced by this packet?

Ans: If the density of an object is greater than the density of a liquid, then the object will sink in the liquid. If the density of an object is less than the density of a liquid, then it will float on the surface of the liquid.

\[Density\text{ }of\text{ }the\text{ }500\text{ }g\text{ }sealed\text{ }packet=\frac{Mass\text{ }of\text{ }the\text{ }packet}{Volume\text{ }of\text{ }the\text{ }packet}\]

\[\Rightarrow Density\text{ }of\text{ }the\text{ }500\text{ }g\text{ }sealed\text{ }packet=\frac{500}{350}\]

\[\Rightarrow Density\text{ }of\text{ }the\text{ }500\text{ }g\text{ }sealed\text{ }packet=1.428gc{{m}^{-3}}\]

The density of the substance is more than the density of water \[\left( 1gc{{m}^{-3}} \right)\].

Hence, the object will sink in water.

Clearly, the mass of water displaced by the packet can be considered equal to the volume of the packet\[=0.350g\].

Class 9th Science Gravitation Class 9 - Quick Overview of Detailed Structure of Topics

Class 9 Science Ch 9 Gravitation - Important Formula and Concepts

The universal law of gravitation: The force of attraction between any two objects is proportional to the product of their masses and inversely proportional to the square of the distance between them. 

Archimedes’ Principle: When a body is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it. 

Where \[G\]is the universal gravitation constant, which is given by:

Weight of the object on the moon = (1/6) × its weight on the earth.

Pressure= Thrust/Area

Benefits of Vedantu’s NCERT Class 9 Science Gravitation Question Answer

Vedantu’s solutions explain all key concepts covered in Ch 9 Science Class 9, including the Universal Law of Gravitation, acceleration due to gravity, the distinction between mass and weight, free fall, and gravitational fields.

Class 9 Science Gravitation Question Answers are presented in a step-by-step format, making it easier for students to follow and understand the problem related to the motion of objects under the influence of the gravitational force of the earth, pressure, and Thrust. 

Vedantu’s NCERT Gravitation Class 9 Questions And Answers help students prepare effectively for their exams. 

The solutions include various types of questions, from multiple-choice to descriptive, ensuring comprehensive exam readiness.

Class 9 Gravitation Question Answers are prepared by Vedantu Master Teachers with a deep understanding of the curriculum and examination patterns. This ensures that the content is accurate, reliable, and aligned with the latest syllabus.

Using Class 9 Gravitation NCERT Solutions, students can save time by quickly finding answers and explanations for their doubts and questions. This allows them to allocate more time to practice and revision.

Vedantu’s Class 9 Chapter 9 Science solutions are available online, making them accessible anytime and anywhere. This flexibility supports continuous learning and allows students to study independently.

Related Study Materials for Class 9 Science Ch 9 Gravitation

Vedantu’s NCERT Class 9 Gravitation NCERT Solutions is an important study material. They provide clear explanations and step-by-step solutions, helping students grasp important concepts like the laws of gravitation, mass, weight, and gravitational force. Focusing on these areas is essential, as they form the chapter's foundation. In previous years, around 7-8 questions on gravitation have been asked in exams, highlighting its importance. By using Gravitation Class 9 Questions And Answers, students can effectively prepare, clear their doubts, and perform well in their exams, ensuring a strong understanding of gravitation.

NCERT Solutions for Class 9 Science - Chapter-Wise Links

NCERT Study Resources for Class 9 Science

FAQs on NCERT Solutions for Class 9 Science Chapter 9- Gravitation

1. How can students understand the features of Gravitational Force Properly?

Chapter 9 Science Class 9 is an important part of the Science syllabus. Focus on the classroom sessions and concentrate on what the teachers are explaining. Study the chapter unit-wise and clear your doubts by using the Science Class 9 NCERT Solutions provided by Vedantu. You will surely understand these newfound concepts well.

2. How can I solve Gravitation problems quickly?

You must practise regularly using the NCERT Solutions Class 9 Science Chapter 9 as a reference and become more efficient. Your speed will automatically increase as you can remember the formulas properly.

3. Why do students prefer using NCERT Solutions for Class 9 Science Chapter 9?

By using the NCERT Solutions for Class 9 Science Gravitation, a student can save time in finding the right answers. They can focus better in preparing the chapter and score higher in the exams by following the ideal answering format recommended by the experts.

4. Why does the Earth not move towards objects due to Gravitation according to Chapter 9 Gravitation of Class 9 Science? 

Newton's third law states, “Every action has its equal and opposite reaction”. It means the force applied by an object on the Earth is equal to the force applied by the earth on the object, but we know that acceleration is inversely proportional to mass. This means when the acceleration is increased, the mass is decreased, or when the mass is increased, the acceleration is decreased. As the mass of the earth is large, the acceleration due to an object is small or negligible. Therefore, it's not noticeable. And the Earth doesn’t seem to be moving.

5. What are the different applications of Archimedes' principle?

The different applications of Archimedes' principle include the following:

It is used in designing ships and submarines.

Lactometers used to determine the purity of a milk sample and hydrometers used to determine the density of a liquid are based on this principle. 

6. Why does the Earth doesn’t move towards objects due to Gravitation according to Chapter 9 Gravitation of Class 9 Science? 

As per Newton's third law, “Every action has its equal and opposite reaction”. It means the force applied by an object on the Earth is equal to the force applied by the earth on the object, but we know that acceleration is inversely proportional to mass. This means when the acceleration is increased, the mass is decreased or when the mass is increased, the acceleration is decreased. As the mass of the earth is large, the acceleration due to an object is small or negligible. Therefore, it's not noticeable. And the Earth doesn’t seem to be moving.

7. What are topics covered in Vedantu’s Class 9 Gravitation NCERT Solutions?

Vedantu’s NCERT Class 9 Science Gravitation Question Answer covers all key concepts such as Newton’s Law of Gravitation, the universal law of gravitation, the relationship between gravitational force, mass, and distance, free fall, mass, weight, and the concept of acceleration due to gravity.

8. Why should I refer to Vedantu’s NCERT Solutions for Gravitation Class 9?

Vedantu’s NCERT Solutions for Gravitation Class 9 offers detailed explanations and step-by-step answers to textbook problems, making it easier to understand complex concepts. They also provide diagrams and illustrative examples that aid in better comprehension.

NCERT Solutions for Class 9 Science

Ncert solutions for class 9.