The Prep Point

  CBSE Class 9 Science Notes Chapter 15 Improvement in Food Resources Facts that Matter Food supplies proteins, carbohydrates, fats, vitamins and minerals, all of which we require for body development, growth and health. Different crops require different climatic conditions, temperature and photoperiods for their growth and completion of their life cycle. Photoperiods are related to the duration of sunlight. Growth of plants and flowers are dependent on sunlight. Successful crop production depends upon many factors such as: Understanding how crops grow and develop. Effect of various nutrients, climate, water on the growth of the plant. Modification and management of each factor for increasing the yield of the crop. The crops which are grown in rainy season (the kharif season, from June to October) are called as kharif crops. Example:  Paddy, soyabean, pigeon pea, maize, cotton, green gram and black gram are kharif crops. The crops which are grown in winter season (the rabi sea...

  CBSE Class 9 Science Notes Chapter 14 Natural Resources Facts that Matter Life exists on earth due to its ambient temperature, water, food and energy from the sun. Lithosphere: The outer crust of the earth is called the lithosphere. Hydrosphere: Sum of all water bodies is called hydrosphere. Atmosphere: Air that covers the earth is called the atmosphere. Biosphere: The life-supporting zone of the earth where the atmosphere, hydrosphere and lithosphere interact and make life possible is called biosphere. It consists of biotic components-living things and abiotic components-non- living things like air, water and soil Air:  It is a mixture of many gases like oxygen, nitrogen, carbon-dioxide, water vapour and other gases. Nitrogen is used by plants for protein synthesis. Oxygen sustains life used for respiration, combustion. Carbon-dioxide used by plants for preparing food by photosynthesis. Water vapour:  provides moisture. Atmosphere:  Acts as a protective blanket ar...

  CBSE Class 9 Science Notes Chapter 13 Why Do we Fall ill Facts that Matter Introduction Health is a state of complete physical, mental and social well-being. Basic conditions for good health: Proper balanced and nutritious diet. Personal hygiene. Clean environment and surroundings. Healthy air, no pollution in the surrounding. Regular exercise. Proper rest. Good standard of living and economic status. Disease:  when the body is not at ease i.e., comfortable then it is said to have a disease. When there is a disease, the functioning or appearance of one or more systems of the body changes. Depending on the duration—disease is classified as acute or chronic. Acute disease:  Diseases that last for only short period of time, e.g., headache, common cold etc. Chronic disease:  Diseases that last for long time,’ are called chronic diseases, e.g., elephantiasis, tuberculosis, etc. Causes of diseases:  Immediate cause and contributory cause. Immediate cause:  The ...

  CBSE Class 9 Science Notes Chapter 12 Sound Facts that Matter A sound is a form of energy which produces a sensation of hearing in our ears. Propagation of Sound:  Sound is produced by vibrating objects. Medium:  The matter or substance through which sound is transmitted is called a medium. It can be solid, liquid or gas. Air is the most common medium for sound propagation. Wave:  A wave is a disturbance that moves through a medium when the particles of the medium set neighbouring particles into motion. They in turn produce similar motion in others. The particles of the medium do not move forward themselves, but the disturbance is carried forward. This is what happens during propagation of sound in a medium, hence sound can be visualised as a wave. Sound waves are characterised by the motion of particles in the medium and are called mechanical waves. When a vibrating object moves forward, it pushes and compresses the air in front of it creating a region of high pre...

  CBSE Class 9 Science Notes Chapter 11 Work, Power and Energy Facts that Matter Work:  When a force acts on an object and the object shows displacement, the force has done work on the object. Two conditions need to be satisfied for work to be done: (i) A force should act on object (a) The object must be displaced Work = Force x Displacement Unit of workdone = Joule = Newton x metre 1 Joule work is said to be done when 1 Newton force is applied on an object and it shows the displacement by 1 meter. Energy The capacity of a body to do work is called the energy of the body. Unit of energy = Joules 1KJ = 1000 J Forms of Energy:  The various forms of energy are potential energy, kinetic energy, heat energy, chemical energy, electrical energy and light energy. Kinetic Energy:  Energy possessed by a body due to its motion. Kinetic energy of an object increases with its speed. Kinetic energy of body moving with a certain velocity = work done on it to make it acquire that ve...

  CBSE Class 9 Science Notes Chapter 10 Gravitation Facts that Matter The universal law of gravitation:  Every object in the universe attracts every other object with a force which is proportional to the product of their masses and inversely proportional to the square of the distance between them. The force is along the line joining the centres of two objects. Let two objects A and B of masses M and m lie at a distance of d from each other as shown in the figure. Let F be the force of attraction between the law of gravitation G is called a universal constant because its value does not depend on the nature of intervening medium or temperature or any other physical variable. S.I. unit of G = Nm 2 /kg 2 Value of G = 6.673 x 10-11 Nm 2 /kg 2  (Found by Henry Cavendish) Importance of universal law of gravitation Universal law of gravitation successfully explained several phenomena like : the force that binds us to the earth. the motion of moon around the earth. the motion of p...

CBSE Class 9 Science Notes Chapter 9 Force and Laws of Motion Facts that Matter Force:  It is a push or pulls on an object that produces an acceleration in the body on which it acts. S.I. unit of force is Newton. A force can do three things on a body. It can change the speed of the body. It can change the direction of motion of a body. It can change the shape of a body. Balanced forces:  Forces are said to be balanced forces if they nullify one another and their resultant force is zero. Frictional force:  The force that always opposes the motion of objects is called a force of friction. The second law of motion:  The rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of the force. Mathematically, Momentum:  The momentum of an object is the product of its mass and velocity and has the same direction as that of the velocity. Its S.I. unit is kg m/s. 1 Newton:  A force of one Newton produces an acceleration...

  CBSE Class 9 Science Notes Chapter 8 Motion Facts that Matter An object is said to be in motion when its position changes with time. We describe the location of an object by specifying a reference point. Motion is relative. The total path covered by an object is said to be the distance travelled by it. The shortest path/distance measured from the initial to the final position of an object is known as the displacement. Uniform motion:  When an object covers equal distances in equal intervals of time, it is said to be in uniform motion. Speed:  The distance travelled by an object in unit time is referred to as speed. Its unit is m/s. Average speed:  For non-uniform motion, the average speed of an object is obtained by dividing the total distance travelled by an object by the total time taken. Velocity:  Velocity is the speed of an object moving indefinite direction. S.I. unit is m/s. Acceleration:  Change in the velocity of an object per unit time. Graphica...