NCERT Books for Class 9 Science Chapter 11

Chapter 11:

NCERT Books for Class 9 Science - Work and Energy - Free PDF Download

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NCERT Books for Class 9 Science Chapter 11

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Work Energy and Power in One-Shot | CBSE Class 9 Physics | Science Chapter 11 | NCERT Solutions

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Work Energy and Power L2 | Kinetic Energy | CBSE Class 9 Science NCERT |Umang Vedantu Class 9 and 10

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A Brief into the Chapter

NCERT Class 9 Science Chapter 11 discusses the concept of work and its relationship with energy and power. Further, we also discuss the conditions necessary to prove that work has been done by an object as well as the calculations involved which form an important aspect of the chapter. This chapter explains the types of energy in function as well as the law of conservation of energy and the commercial unit of work and energy.

The definition of work in real life and in science is very different from one another. Suppose a person holds a huge boulder with his hands over his head, we know that he has exerted force and used some energy to do so. But in science, work is not done here. In this case, work would be considered done by the person only if he fulfilled two main conditions- a) force must be exerted on the object and b) the force applied must displace the object in the direction of force. This means that only if the force acts on the object and makes it move and cover some distance will work be done. Next, the person has used energy to do the work. Energy means the capability of an object to do work. This means that the object which has done the work (person) loses the energy while the object on which the work has been done has gained the energy.

The other topics discussed in this chapter have been segmented concisely with examples and numerical given to explain each concept. They are:

11.1- Work
11.1.1- Not much ‘work’ in spite of working hard
11.1.2- Scientific conception of work
11.1.3- Work done by a constant force
11.2- Energy
11.2.1- Forms of Energy
11.2.2- Kinetic Energy
11.2.3- Potential Energy
11.2.4- Potential Energy of an object at a height
11.2.5- Are various energy forms interconvertible?
11.2.6- Law of conservation of Energy
11.3- Rate of Doing work
11.3.1- Commercial unit of Work

Students will find chapter 11 of the class 9 Science NCERT book right on this page.

FAQs on NCERT Books for Class 9 Science Chapter 11

1. What is the formula for work done by a constant force as discussed in chapter 11 of class 9 Science NCERT book?

Let us say that an object has been moved by a person using force F which has displaced the object to move in a direction of the force across a certain distance s. The work done here is marked as W. Here only the magnitude of the displacement is checked and not the direction. Hence the formula would be the work done being equal to the magnitude of the force applied multiplied by the distance moved by the object, i.e. W= F x s

2. How many types of energy are mentioned in NCERT books for class 9 chapter 11?

There are different types of energy like heat energy, chemical energy, light energy, etc., but here are two types of energy which have been mentioned in this chapter. They are:

KINETIC ENERGY- Under kinetic energy, the energy possessed by an object is due to its motion. For example, a plane flying or a man running. The kinetic energy increases with an increase in speed. The formula for kinetic energy is Ek= ½ mv²where m is the mass and v is the velocity.
POTENTIAL ENERGY- Under the potential energy, the energy spent on the object is stored within the object potential energy. For example, stretching a rubber band or winding a toy car. The potential energy of an object at a height is called gravitational potential energy since work has been done on the object against gravity.

3. What is the Law of Conservation of Energy as discussed in chapter 11 of class 9 Science NCERT book?

As we know that energy is the ability of the object to do work. In this case, the law of conservation of energy states that energy cannot be created nor destroyed. It can only be converted to different forms. Whenever the energy is transformed, the total energy remains the same. Hence The energy before and after the transformation remains unchanged. For example, an object falling from a height will have zero kinetic energy due to zero velocity which will be converted into potential energy and finally before hitting the ground, it will change into kinetic energy.

4. What is the rate for doing work in chapter 11 of NCERT class 9 science?

Rate of doing work is also known as power. Here, power measures the speed of work down since not all machines transfer the same amount of energy. Hence, in this case, let us assume that an agent has done some work W in time t, then the power P is calculated by the formula P= W/t. The S.I. unit of power is watt at the rate of 1 joules per second, i.e., 1 J/s.

5. Where can we get NCERT Books Free Download for Class 9 Science Chapter 11 - Work and Energy?

Vedantu has made it very easy as possible for students to download study materials, mock/sample papers and other resources for free. Since NCERT books are the most recommended books by CBSE, all such resources are made available by the CBSE board for easy access by students so that students do not search along too many websites for different study materials. Students can go to the Vedantu website, click on the resources and download the PDF format of the document required and study offline.