Complete Explanation of CBSE Notes
Improvement in Food Resources Class 9 Notes explains how the technology and practices for growing food have changed over the ages – from primitive tools to state of the art farming equipment and practices which increases yield and quality.
Natural Resources Class 9 Notes explain the various resources found on Earth and their implications on life. Some resources are more precious than others, such as gold and diamonds, while others are quite abundant, but still, hold commercial significance, such as iron and nickel. On a larger, planetary scale, water is the most precious resource on earth. It is crucial as life on earth wouldn’t exist without water.
Humans have been falling sick since times immemorial. Before science and technology, humans have attributed sickness to the supernatural, for instance, when there was a tuberculosis outbreak during the 19th century, people had associated its symptoms with vampirism. This is due to the fact that the patients often had very pale, deathly complexion and they would frequently cough up blood. But advancements in medicine and technology have provided a deeper insight into causative factors and the precautions one should take. Please refer Why Do we Fall ill Class 9 Notes for more revision notes.
There are various sources of sounds around us – from the birds, the leaves rustling in the wind to the cars and the sounds of our own voice. In science, we define sound as a form of energy that travels in waves. A body produces soundwaves and these vibrations cause the medium around the object to vibrate. We pick up these vibrations as audible cues. Please refer Sound Class 9 Notes for more revision notes.
Work, Power And Energy Class 9 Notes describes the meaning of work and energy, and how they are related to each other. The term work might imply working hard, such as studying for an exam, or a performing a job. However, in science, the term “work” has a very different meaning. It essentially is a term used to define the movement of an object a certain distance using an external force.
Gravitation Class 9 Notes explains how gravity works in intricate detail. We are aware of the fact that the earth has gravity and it keeps every object tethered to the surface. But what exactly is gravity and what are its implications?
What is Gravity?
Gravity is essentially a force which attracts a body towards to centre of another physical body having mass. Among the various fundamental forces, gravity is the weakest and its presence is almost imperceptible by us. But on an astronomical scale, it is quite a powerful force. For instance, black holes are the end stage of stars that had very large masses. These cosmic structures have gravity so strong that even light cannot escape. As a result, black holes are not visible.
Force and Laws of Motion Class 9 Notes introduce the laws set down by Isaac Newton and the concept of force. These are essentially the fundamentals of physics and forms the backbone of every physical context known to humans. But how do we define the concept of force and what do the laws of motion imply?
Describing Motion:
If a body is constantly changing its position with respect to time or point of reference, then, that body is said to be in motion. There are various types of motion, namely:
It occurs when equal distances are covered in equal intervals of time by a body. Light travels in uniform motion through a vacuum.
Unlike uniform motion, a body travels unequal distances in equal intervals of time. A car moving through traffic constitutes non-uniform motion.
This is essentially a type of motion that repeats itself at periodic intervals of time. A vibrating tuning fork is an example of periodic motion
This is a form of periodic motion that occurs in a regular cycle. A sine wave, the swing of a pendulum are examples of oscillatory motion.
Motion Class 9 Notes also explains the concept of motion along a straight line, one of the most simple types of motion. It is also called linear motion or rectilinear motion.
There are a variety of factors such as geographic, biotic, abiotic that affect the diversity in living organisms. For instance, the earliest known ancestors of whales (not direct) were similar to today’s dogs. But over the course of many aeons, limbs transformed to flippers and fins, size increased drastically, resulting in the evolution of whales as we know them today. Please refer Diversity in Living Organisms Class 9 Notes for more revision notes.
Tissues Class 9 Notes elaborates that all living organisms are made up of cells. When these cells bunch up and perform a similar function, they give rise to tissues. Consequently, these tissues are not the same in all organisms. Plants, for instance, are stationary. This means that their tissue composition is vastly different to that of animals.
CBSE Revision Notes