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# NCERT Books for Class 9 Science Chapter 10

Last updated date: 10th Aug 2024
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## NCERT Books for Class 9 Science - Gravitation - Free PDF Download

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NCERT Books for Class 9 Science Chapter 10
Gravitation L9 | NCERT Exercises, Questions 16, 17 & 18 | CBSE Class 9 Physics | Science Chapter 10
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## A brief into the Chapter

NCERT Books for Class 9 Chapter 10 explains the concept of Gravitation and how the Universal Law of Gravitation is important. It also discusses the calculation of the gravitational force and its influence on the objects on earth. Also, concepts of mass and weight have been explained concisely alongside buoyancy, relative density and Archimedes’ Principle.

Newton observed that objects, when dropped from a height, always fall on earth which was later known as the Gravitational force. Even the moon, moving in a circular motion around the earth, is attracted to the earth due to the gravitational pull but this pull is not the same as the former example. Despite the same force being responsible for both the movements, in the case of the moon, it is the centripetal force that causes the circular movement else it would move in a straight line. According to the Universal Law of Gravitation,  the force of attraction between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Mathematically, the formula is F = GMm/d2 where G is the universal gravitation constant, F is the force of attraction between two objects, M and m being the masses of each object and d is the distance. The value of G is 6.673x 10-11 N m2/kg2. There are several examples of numericals to explain the concepts for students to understand. The other topics discussed in this chapter are:

• 10.2- Free Fall

• 10.2.1- To calculate the value of g

• 10.2.2- Motion of objects under the influence of the gravitational force of the earth

• 10.3- Mass

• 10.4- Weight

• 10.4.1- Weight of the object on the moon

• 10.5- Thrust and Pressure

• 10.5.1- Pressure of Fluids

• 10.5.2- Buoyancy

• 10.5.3- Why do objects float or sink when placed on the surface of the water?

• 10.6- Archimedes’ Principle

• 10.7- Relative Density

The students can find chapter 10 of class 9 Science NCERT book here on this page.

## FAQs on NCERT Books for Class 9 Science Chapter 10

1. What is the importance of the Universal Law of Gravitational Force as discussed in chapter 10 of class 9 Science NCERT book?

As the Law of Gravitational Force suggests that every object attracts another object in proportion to their mass and inversely proportion to their square distance between them with the force in line with the centers of both the objects, this is an important force which has led to several phenomenons like:

• A force binding objects to the earth

• Movement of the moon around the earth

• Movement of planets around the sun

• Movement of tides between moon and earth (high tides and Low tides)

2. Are numericals to be practised for NCERT class 9 Science chapter 10 Gravitation?

The numerical has to be practiced regularly. In this chapter, the derivations of different formulas used to calculate the gravitational force, free fall, the weight of objects on the earth and moon, thrust and pressure and relative density, can be very confusing and difficult to understand in the beginning. Hence students must study every line of all the topics along with the equations in play so that the students can solve the numerical with ease. Students can download NCERT Books Free Download Class 9 Science Chapter 10 from Vedanu.com in PDF format.

3. What is the formula for Thrust and Pressure as discussed in chapter 10 of class 9 Science NCERT book?

Weight is the force acting on an object vertically downwards. A thrust is when the weight acts on an object perpendicular to the surface. When we stand, the force acts on an area equal to the area of our feet but when we lie down, the distribution of force is different in different parts of our body on the surface. Pressure is thrust per unit area which is derived as P= thrust/area. When we substitute thrust and area in the above formula, we get the SI unit of pressure as N/m2 where N is newton. The SI unit of pressure is called Pascal.

4. Why do some objects float or sink when placed on the surface of the water as discussed in chapter 10 of class 9 Science NCERT book?

When the upthrust of water is greater than the weight/ gravitational pull, then the object floats. But when the gravitational pull is more than the upthrust, the object sinks. The best examples are given through a cork and a nail. The diagrams of the experiments on both these objects have been given in the NCERT class 9 science chapter 10 Gravitation. This is due to the densities of the objects which is described as mass per unit volume. The density of the nail is higher than water as compared to the cork which has a lesser density.

5. Are there any exercises given after the NCERT class 9 chapter 10 Gravitation?

Yes, there is an exercise given which will be helpful for students to analyse their understanding of the chapter. The questions are mostly in the form of numerical and short answer types. Students should also practise the examples and other similar numerical related to the topics in between the chapters so that they can simultaneously revise and practice the questions for quicker grasping of the topics which is the reason why CBSE recommends NCERTS to schools. For more such exercises, follow the sample papers by Vedantu for free.