CBSE ADDA

CBSE MATH STUDY: 8th maths :8th Linear Equations of one or two Vari... : 8th Mathematics JSUNIL TUTORIAL,SAMASTIPUR   What is an equation? A statement which contains the equ...

Changes around us are continuous process .  Some changes occur naturally and some changes can be brought about by us. Such changes are: Rusting of iron, change of the state of water, Burning of wood, Growth of nail and hair, Blooming of flower and change in day and night ,season change, What are different types of changes? 1. Reversible changes : Changes that can be reversed is called Reversible changes. Example: water changes into ice on cooling, wax change into liquid on heating, blowing of balloon  2. Irreversible changes: Changes that cannot be reversed is called irreversible changes. Like Milk change in to curd, Iron changes to rust, Burning of paper, cooking of food, Growth of plant and animals, weathering of rocks, wear and tear of tires. 3. Physical changes : Changes in which physical properties like shape, size and state changes without formation of new substance is called Physical changes. It is a type of reversible changes. e.g. Melting of wax, solution of su

Q. What is luster? Ans: Materials around us have a particular type of shine called Luster like gold, silver, aluminum etc Q. Some metal can hammered into thin sheet without breaking into pieces. Name this property of metals? Ans: Malleability. Q. Some metal drawn into thin wire. Name this property of metals?  Ans: Ductility. Q. Name material used to make chalk?  Ans: Calcium carbonate Q. Why do houses have cement floor?  Ans: Houses have cement floor because it can polished to make attractive. Q. Define soluble and insoluble substance? Ans: Material that mixed with water is called soluble e.g. acid, base, milk, lemon juice, sugar and alcohol. Material that do not mixed with water is called insoluble like oil, sand, alum etc  Q. what will happen if you drop piece of chalk and sponge in to glass of water? Ans: Chalk and sponge absorb water due to gap between their particles. Q. Which material you prefer to use for furniture? Ans: Wood and Metal  as

9 th   physics:  Force and laws of Motion 1. An object of mass 2 kg is sliding with a constant velocity of 4 m/ s   on a frictionless horizontal table. The force required to keep the object moving with the same velocity is (a) 32 N               (b) 0 N                (c) 2 N                 (d) 8 N                  Ans: (b]        2. Rocket works on the principle of conservation of (a) mass              (b)energy            (c) momentum    (d) velocity          Ans:  [c] 3.A car is moving at 45 km/hr.A constant force acts on the car for 10 sc .So that it's velocity becomes 63 km/hr .The distance travelled by car during this interval of 10 sec is : a) 100 m         b) 150 m              c) 200 m        d) 50 m                       Ans:  [b]      4. What is the definition of balanced and unbalanced force? Ans:   When two equal forces acting on an object in opposite directions called balanced force.   When something does not move the forc