 # 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. They 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

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

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 important questions given below and learn about some 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.

Question 4: Where do we get energy from?

Answer: The Sun is the biggest natural and primary source of energy for us. Many other secondary sources are derived from the Sun. We can also get energy from the interior of the earth and from tides of the sea.

Question 5: A book of mass 1 kg is raised through a height ‘h’. If the potential energy increased by 49 J, find the height raised.

Answer: Given that the increase in potential energy = mgh
Here, mgh = 49 J
That is (1)(9.8)h = 49 J
The height raised, h = (49) / (1x 9.8)= 5m

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