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# NCERT Exemplar Class 9 Science Chapter 11 Solutions: Work And Energy

NCERT Exemplar Class 9 Science Solutions for Chapter 11 ’Work and Energy’ provide you with the whole knowledge related to the chapter. Chapter 11 of NCERT Exemplar Class 9 Science covers all the necessary explanations on concepts of work, energy, forms of energy, the law of conservation of energy, power, a commercial unit of energy, etc. All these topics will always make you realize that science is present everywhere in our lives.

NCERT Exemplar Class 9 Science Chapter 11 covers a variety of problems like multiple-choice questions, short answer questions, and long answer questions. There are 28 questions in total. Apart from the theoretical questions, the exercise also covers numerical questions that are important for your competitive exams. These questions ensure a deeper understanding of the chapter and almost cover every topic.

Our subject matter experts of Science have years of experience and they strive for providing you with a better learning experience. Instasolv’s NCERT Exemplar solutions are written in simple language and cover all the necessary information about the topics. The experts at Instasolv always try to find the best possible answer to your problems. Take a look at the important topics of the chapter before you start solving the NCERT Exemplar problems.

## Important Topics for NCERT Exemplar Class 9 Science Solutions Chapter 11: Work and Energy

Just like the title of the chapter, the concepts covered in this chapter are really interesting. The chapter also provides you with some examples from our everyday life that work on these topics. Some of the important topics are :

Work

Work is defined as a force that causes the displacement of an object.

In other words, Work done = Force X displacement or W = F X d

The unit of work is joule: 1 joule = 1 newton × 1 meter

Energy

The capability of an object to do the work is defined as Energy. Energy possesses the same unit as that of work i.e Joule

Forms of energy

• Kinetic Energy: The kinetic energy of an object is defined as energy which happens due to the motion of its object. The kinetic energy of an object increases with speed.

For instance, A moving car or a bullet from a gun.

The kinetic energy of an object with mass m and a uniform velocity v is = ½ mv2. Through this formula, we see that kinetic energy is directly proportional to mass and velocity.

• Potential Energy: The energy possessed by an object due to its change in position or shape is defined as the potential energy and the potential energy at height is called gravitational potential energy of an object. The gravitational potential energy of mass m raised through a height h from the earth’s surface is given by mgh.
• Other forms of energy include heat energy, chemical energy, electrical energy, light energy and mechanical energy (kinetic energy + potential energy)

Law of conservation of energy

According to the law of conservation of energy, energy can neither be created nor destroyed. The energy can only be transformed from one form to the other. The total energy before and after the transformation is always constant.

Power

In simple words, power is defined as the rate of doing work.

Power = work/time

P = W/T

The unit of power is Watt or Joule/sec

Commercial Unit of Energy

Kilowatt per hour or kWh is the commercial unit of energy and it is defined as the energy used in one hour at the rate of 1kW.

### Exercise Discussion of NCERT Exemplar Class 9 Science Solutions Chapter 11: Work and Energy

• The exercise of this chapter of NCERT Class 9 Exemplar contains 28 questions in total. The purpose of these questions is to provide in-depth learning to you. This exercise is really helpful for competitive exams as well.
• The first set of questions consists of multiple-choice questions that are 9 in number. MCQs assess your complete understanding of the topic. The concepts covered in this exercise include force, displacement, kinetic energy, acceleration, SI unit of energy, identifying the work done or the energy spent.
•  The second set of questions comprises 10 short answer questions. These questions are generally short numerical which assesses your quantitative skills. You can also find some questions that require general justification.
• The third set of questions contains 8 long answer questions. However, this set contains only numerical questions related to work, energy, and power. These questions test your, logical and quantitative skills.

### Why Use NCERT Exemplar Class 9 Science Solutions Chapter 11: Work and Energy by Instasolv?

• The NCERT Exemplar Problems and Solutions for Class 9 Science Chapter 11 will work as the best reference study material for you as it contains the best answers to all the questions which might appear in your exams.
• All these solutions are curated by a team of professionals who have excelled in the field of education.
• Our experts aim at clearing all your doubts regarding the chapter and make sure that you gain in-depth knowledge of concepts through NCERT Exemplar solutions.
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