NCERT Solutions for Class 9 Science Chapter 10 Gravitation

Q:

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

A:

The buoyant force acts in the upward direction for an object immersed in a liquid.

Q:

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

A:

Gravitational force acting between the earth and an object is called the weight of the object.

Q:

What is the importance of universal law of gravitation?

A:

Importance of the universal law of gravitation

(i) It binds us to the earth.

(ii) It explains the motion of moon around the earth.

(iii) It explains the motion of planets around the sun.

Q:

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

A:

A plastic block under the water experiences two forces. One is the gravitational force, which pulls the block downwards and the other is the buoyant force which pushes the block upwards. If the upward buoyant force is greater than the downward gravitational force, then the block comes up to the surface of the water as soon as it is released within water.

Q:

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

A:

When the paper is crumbled in the shape of a ball, its surface area decreases. Thus, air does not exert too much resistance to its motion and it falls faster than the sheet of paper.

Q:

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.]

A:

As the gold purchased at the equator weighs less than at the poles so the value of acceleration due to gravity (g) for an object is greater at poles than at the equator. Therefore, Amit’s friend will not agree with the weight of the gold bought.

Q:

What is the acceleration of free fall?

A:

An object falling towards the earth under the effect of gravitation is said to be in free fall. Acceleration of free fall also called acceleration due to gravity is 9.8 ms−2 near the surface of earth. It is constant for all the objects.

Q:

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

A:

The Earth and the moon exert equal gravitational forces to each other. Due to heavier mass of Earth, it accelerates at a rate lesser than the acceleration rate of the moon towards the Earth. Therefore, the Earth does not move towards the moon.

Q:

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?

A:

The universal law of gravitation states that two objects attract each other with equal forces, but in opposite directions. Hence, the Earth attracts the moon with an equal force with which the moon attracts the earth.

Q:

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

A:

All the objects fall towards the ground under the acceleration due to gravity and this acceleration is constant and does not depend upon the mass of the falling object. Thus, a heavy object does not fall faster than a light object.

Q:

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?

A:

(i) According to universal law of gravitation, force is directly proportional to the product of the masses. If the mass of one object is doubled, then the gravitational force will also get doubled.

(ii) According to universal law of gravitation, force is inversely proportional to the square of the distance between the objects. If the distance is doubled, then the gravitational force becomes one-fourth of its original value. Also, if the distance gets tripled, then the gravitational force becomes one-ninth of its original value.

(iii) Force is directly proportional to the product of the masses. When masses of both the objects are doubled, then the gravitational force becomes four times.

Q:

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

A:

Q:

The volume of a 50 g sealed packet is 350 cm3. 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?

A:

Q:

The volume of 50 g of a substance is 20 cm3. If the density of water is 1 g cm−3, will the substance float or sink?

A:

Q:

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

A:

Q:

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.

A:

Q:

Calculate the force of gravitation between the earth and the Sun, given that the mass of the earth = 6 × 1024 kg and of the Sun = 2 × 1030 kg. The average distance between the two is 1.5 × 1011 m.

A:

Q:

A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s2, find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?

A:

Q:

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

A:

Q:

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.

A:

Q:

A:

Q:

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 × 1024 kg and radius of the earth is 6.4 × 106 m.)

A:

Benefits of NCERT Solutions

Following are some of the benefits of using NCERT Solutions by Extramarks.

1. They are developed by our experts with the right approach for precisely answering the textbook questions.

2. They are free of cost and available online to help class 9 students.

3. They not only explain every topic but also prepare students for further examinations. 

4. They are proven to be helpful to students in their exam preparation, homework and competitive exams.

5. They will help in understanding the solutions and the methodology of writing the answers in the exams.

Tips & Strategies for Class 9 Exam Preparation

1. Jot down important chapters or topics for your exam preparation.

2. Learn from the best teachers with Extramarks and clear your doubts instantly.

3. While practicing, refer to NCERT Solutions for class 9 to understand step-by-step solutions to all questions.

4. Solve as many sample papers as you can to prepare well for the exams.

5. Lastly, don’t panic. Try to meditate at least for 15 minutes every day- it will help you retain things better.

Why opt for Extramarks NCERT Solutions for Class 9 ?

Extramarks provide NCERT Solutions for all subjects at your fingertips. These solutions are designed by subject matter experts and provide solutions to every NCERT textbook questions. These solutions help students in their exam preparation and home assignments. We hope NCERT Solutions for class 9 will come in handy for every student and help them understand everything in a better way.

Frequently Asked Questions

product
When to refer to NCERT Solutions for Class 9?

You can refer to NCERT solutions for class 9 anytime during your academic year. Whether you are preparing for class tests or unit tests or pre-board exams, you can refer to the class 9 NCERT solutions easily. The NCERT solutions are available on Extramarks - The Learning App and Extramarks website in the footer section.

What can I do to get better marks in Class 9?

If you want to gain good marks in Class 9 examination then we suggest that you go through NCERT books solutions for class 9 listed on the Extramarks website. The solutions are self-explanatory and written in easy to understand language so you can easily learn and ace your exams with the help of these solutions.

Why are the NCERT solutions Important for Class 9?

NCERT solutions class 9 are self-explanatory and form the basis of examination. Since the exam syllabus is taken directly out of the NCERT books, studying NCERT solutions becomes important to prepare for the exams.

What are some expert tips to score good marks in Class 9 CBSE?

If you want to score good marks in Class 9, follow these tips:

1. Study NCERT Solutions from Extramarks website.

2. Study using Extramarks - The Learning App, practice using the sample papers, and prepare through the interactive video modules.

3. Prepare a timetable and schedule your subjects and save time for revision.. Get concept clarity by tuning in to the Extramarks live classes.

How to Prepare for Competitive Exam Through NCERT Class 9 Solutions?

NCERT solutions for Class 9 science are amazingly useful for JEE and NEET and if you are preparing for any other competitive exam then consider studying through the NCERT solutions listed on the Extramarks website. You can also study the 9-10 and other classes syllabus on Extramarks - The Learning App.

Start Your
7-Days Free Trial
and experience it yourself
Start Trial
Play StoreApp Store
Flying Girl
A subscription
that’s worth your
money
Get the best classroom experience on
India’s leading learning platform

Get
in touch

Have a query about our services?
Get in touch with us and we will
guide you through a new world of
redefined learning

Union
Get OTP
Submit