Class 9th CBSE

Improvement of Crop Resources * Green revolution contributed to increased food grain production. * White revolution contributed to increased availability of milk. * The gradual increase in food production can be brought about by crop variety improvement, crop production improvement and crop protection management. * Crop variety improvement involves selecting a high yield crop variety ... Read more

Natural Resources * The region where the atmosphere, hydrosphere and lithosphere interact and supports life is called biosphere. * Air is mixture of gases like nitrogen, oxygen, carbon dioxide and water vapour. * Water exists as seas and oceans on the Earth’s surface and as water vapour in the atmosphere. * Soil is a mixture ... Read more

Diseases * Health is a state of physical, mental and social well being. * Disease is an unhealthy condition caused by microorganisms, improper diet or is inherited. * Bacteria cause diseases like typhoid, cholera, tuberculosis and anthrax. * Viruses cause the common cold, influenza, dengue fever, AIDS and rabies. * Fungi cause skin infections. * ... Read more

Production and Propagation of Sound * Sound is a form of energy that produces the sensation of hearing in our ears. * Sound is produced due to the vibration of objects. * Intensity of sound is the amount of sound energy incident per unit time per unit area. * Sound propagates through a medium. * ... Read more

Work * Work done by force acting on an object is equal to the magnitude of the force multiplied by the displacement of the direction of the force. Conditions for work to be done: *  A net force should act on an object. *  The object must be displaced in the direction of the net ... Read more

Kepler’s Law of Gravitation * To resolve shortcomings of the models propounded by Ptolemy and Copernicus, * Kepler propounded three laws on planetary motion. * Kepler’s first law, the law of orbits, states that the orbit of a planet is an ellipse with the sun at one of the foci. * An ellipse is a ... Read more

Force * Force is an agent that tries, successfully or unsuccessfully, to move a body at restor to stop a moving body. * A force can change the state of a body at rest, the state of motion of a body under motion, the direction of motion of a moving body or the shape of ... Read more