AP Board Class 9 Physical Science Chapter 9 Work And Energy

In Andhra Pradesh Board class 9 Physical Science Chapter 9 students will examine the concepts of work, energy and power more carefully and in greater detail. The will learn the scientific meaning of these terms as well as understand the important topics related to them. The chapter talks about topics like;

  • Definition of Work Energy and Power in science.
  • Sources and Forms of Energy
  • Kinetic and Potential Energy
  • Mechanical Energy


Work is defined as a force that causes the movement or displacement of a stationary object. Generally, there are two conditions that need to be fulfilled if work is to be done. The first one is that a force should act on the object. The second one is that the object must be displaced or there must be a change in the position of the object. Work is a scalar quantity as it has only magnitude and no direction.


Energy is commonly defined as the capacity or ability to do work. The sun is the main source of energy. However, there are other secondary sources like tides of the sea and others.

Forms of Energy

Energy can be found in different forms like light energy, sound energy, electrical energy, thermal energy, magnetic energy, mechanical energy, amongst others. The main forms though include kinetic and potential energy.

Kinetic and Potential Energy

The energy possessed by an object as a result of its motion is called kinetic energy. Likewise, potential energy is the energy possessed by an object given its shape or position.

Mechanical Energy

Mechanical energy is the sum of the kinetic energy and the potential energy of an object.

Students can quickly go through some of the important questions given below and learn about some of the additional chapter topics.

Question 1: Define Power.

Answer: Power is defined as the rate of doing work or the rate of transfer of energy.

Question 2: What is the unit of work?

Answer: The unit of work is the joule (J).

Question 3: State the principle of conservation of energy.

Answer: According to the law of conservation of energy, energy can neither be created nor destroyed. However, energy can be changed from one form to another.

Students can keep visiting BYJU’s to learn all the important class 9 science topics and access various Andhra board study materials and more.

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Practise This Question

An element X reacts with dilute H2SO4  as well as with NaOH to produce salt and H2(g).  Hence, it may be concluded that:

A.            X is an electropositive element.
B.            Oxide of X is basic in nature
C.            Oxide of X is acidic in nature.
D.            X is an electronegative element.