# Current Affairs 9th Class

#### Why Do We Fall Ill

Why do we Fall Ill   Health is the real wealth. But health and disease are among the most complicated issues in our life. We have to deal with this issue in our life more often. The most important thing to know is that why we fall ill? It has been rightly said prevention is better than cure. The various organ systems in our body work smoothly to keep us healthy.   Wealth and Its Failure Health is an idea of being well. A good health allows us to work well physically, mentally and socially. A good health enables us to cope up with the social, mental and physical pressure without any difficulty. To keep ourselves fit and healthy we must take a balanced diet, regular exercise and cleanliness in and around us. If we do not follow the above mentioned points then we may fall ill. A disease can also be caused because of the malfunctioning of some nutrients or failure of our organs.   Individual and Community Health As we have mentioned earlier that health means a state of physical, mental and social well-being, but it cannot be achieved at an individual level. The health of all the organisms depends on the environment and their surroundings. We live in a society because our social environment is an important part of our individual health. In the community, physical environment is directly related to social environment. There are various agencies in our communities that are responsible for providing cleanliness. If they will network properly then we cannot expect healthy life. For example, in a city if garbage is not dumped properly or drains are not cleaned then our community can become a breeding place for disease causing bacteria and germs. In a community, the availability of clean drinking water, adequate nutritious food, social equality and harmony needs to be provided to keep all the people healthy.   Disease and Its Causes There are various organ systems in our body that work collectively to keep us healthy. A disease can occur when the normal state of a man is disturbed or a particular organ or organ system starts malfunctioning. The cause of disease arise from person to person and from place to place. The following table provides a list of disease in human and its causes:
Type of disease Causes of disease Example
Physical more...

#### Diversity in Living Organisms

Diversity in Living Organisms   Diversity in Living Organism This world is full of living and non-living things. Large variety of living organisms is found on this planet. There is a great diversity among them. From the microorganisms to well-developed animals, one can notice the diversity at all levels.   Basis of Classification Classification is a method of arranging organisms into groups or sets on the basis of similarities and differences. The study of classification is known as taxonomy. The process of classification began hundreds of years ago. First animals were classified according to whether they lived on Land, in water or in the air, but this classification was not adequate. So the need of more accurate form classification was realised and thus some characteristics were used as a basis for making the broadest divisions for making groups and subgroups.   Classification and Evolution All living things are categorised on the basis of their body design the and function. The characteristics that came into existence earlier are likely to be more basic than characteristics that have come into existence later. This clearly indicates that the classification of life forms is directly and very closely related to the evolution. Charles Darwin the renowned biologist first described the idea of evolution in 1859 in his book “The Origin of Species”.   Hierarchy of Classification R. H. in 1969 proposed five kingdom classification. They are as following: Five Kingdom Classification
Characters Monera Protista Fungi Plantae Animalia
Cell type Prokaryotic Eukaryotic Eukaryotic Eukaryotic more...

#### Force and Motion

Force and Motion   Motion The body that is in motion changes its position with time. Therefore, a body is said to be in motion when its position changes continuously with respect to a stationary object taken as a reference point.             Car in motion   Distance The distance travelled by a body is the actual length of the path covered by a moving body irrespective of the direction in which body travels.   Displacement When a body moves from one position to another position, the shortest distance between initial and final position of the body along with the direction is known as its displacement.                 The actual length of the path travelled to reach R, starting from P is PQ + QR = 8 + 6 = 14 km. So, 14 km is the distance travelled by a person.   The shortest distance from P to R is 10 Km, which is the displacement from P to R in north direction.   Scalar Quantity A physical quantity having only magnitude or size is known as scalar quantity. It does not have direction. For example, distance.   Vector Quantity A physical quantity having magnitude or size and direction is known as vector quantity. For example, displacement.   Types of Motion The following are the different types of motion:   Uniform Motion If a body travels equal distance in equal intervals of time, no matter how small these time intervals are then it is called uniform motion.   Distance - time graph for a body having uniform motion   Non Uniform Motion If a body travels unequal distance in equal intervals of time then it is called non uniform motion.   Distance - time graph for a body having non uniform motion   Speed, Velocity and Acceleration Speed The distance travelled by a body per unit time is called speed.             Speed = Distance / Time taken The S.I. unit of speed is metre per second (m/s).   Example: Bus travels a distance of 200 km in 8 hours, then calculate the speed of the bus.   Solution: Speed = 200 km/B hours Speed = 25 km/h   Average Speed The average speed of a body is the total distance travelled divided by the total time taken to cover this distance.        $\text{Average}\,\text{speed}\,\text{=}\,\,\frac{\text{Total}\,\text{distance}\,\text{travelled}}{\text{Total}\,\text{time}\,\text{taken}}$   Note:     (i) When the distance travelled in two cases is same, then             ${{\text{V}}_{\text{av}}}\,\text{=}\,\,\frac{\text{2}{{\text{V}}_{\text{1}}}{{\text{V}}_{\text{2}}}}{{{\text{V}}_{\text{1}}}\text{+}{{\text{V}}_{\text{2}}}}$ (ii)When time taken in two cases is same, then ${{\text{V}}_{\text{av}}}\,\text{=}\,\,\frac{{{\text{V}}_{\text{1}}}\text{+}{{\text{V}}_{\text{2}}}}{\text{2}}$   Example: A bus travels 40 km at a uniform speed of 40 km/h and the next 40 km at a uniform speed of 20 km/h. Find the average speed.   Solution: The time taken to travel the first 40 km is: Time taken = 40/40 more...

#### Gravitation

Gravitation   Gravitation Every object in the universe attracts every other object with a certain force that is called gravitational force. The masses of the objects decide the amount of gravitational force a body can have. When we throw a stone in upward direction, it comes down after attaining a certain height. The earth pulls the stone towards its centre. The stone also pulls the earth toward it with the same force. As mass of earth is very large therefore the acceleration produced becomes negligible. Due to this reason we do not see the earth moving towards the stone.   When we throw an object in upward direction it comes down automatically. This happens because of the force of gravitation. Actually the earth exerts a force of attraction that is called gravity on the object and pulls it down.   The gravitational force was discovered by Sir Isaac Newton. One day he was sitting under apple tree, suddenly an apple fell down from the tree. He started thinking about it. He concluded that the earth has certain force that attracted the apple. Finally he concluded that the earth attracts all the objects towards its centre and this force of attraction is called gravitational force of the earth or the gravity. The gravitational force of the earth is responsible for many phenomenons that take place around us. For example, the gravitational force is responsible for holding the atmosphere of the earth, falling of rain on the earth, flowing water in the rivers, walking, etc.   Universal Law of Gravitation The great scientist Newton has given us the universal law of gravitation. According to this law every object in the universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. The direction of the force is along the line joining the centres of two objects.     Gravitational force is directed along the line joining the centre of uniform objects   Let two objects P and Q of masses M and m lie at a distanced from each other, as shown in the above figure. Suppose the force of attraction between two objects is F. As per the universal law of gravitation, the force between the two objects is directly proportional to the product of their masses. Therefore, $F\,\,\alpha \,\,\frac{1}{{{d}^{2}}}\,\,M\times m$             …(1) The force between two objects is inversely proportional to the square of the distance between them. Therefore, $F\,\,\alpha \,\,\frac{M\times m}{{{d}^{2}}}$                 …(2) From equation (1) and (2) we get $F\,\,\alpha \,\,\frac{M\times m}{{{d}^{2}}}$ Or, $F=G\,\,\frac{M\times m}{{{d}^{2}}}$                  … (3) Where G is constant of proportionality, it is called the universal gravitational constant. The value of G is $6.673\times {{10}^{-11}}$. $N{{m}^{2}}/k{{g}^{2}}$ The S. I. unit of G can be obtained by substituting the units of force, distance and mass in equation (3) as N ${{m}^{2}}k{{g}^{2}}$   Free Fall When an object falls more...

#### Work, Energy and Sound

Work, Energy and Sound   Work Physics work refers to any activity that produce motion. Work is done only when the resultant force and displacement are not zero. The amount of work done by a particular force largely depends on the two factors that are magnitude of the force applied and displacement of the  We can say that work done in moving a body is equal to the product offeree exerted on the body and the displacement moved by the body in the direction of force.               $Work\,\,=\,\,Force\times \,\,Displacement$             OR             $W\,\,=\,\,F\,\,\times \,\,S$   The S. I. unit of work is joule. If a force of 1 Newton moves a body through a displacement of 1 m in its own direction then the work done is known as 1 joule.             $\text{1 joule = 1N }\times \text{ 1 m}$             Work is a scalar quantity. When a ball is thrown up, its motion is opposed by the earth's gravity. In such case, the work done by the gravitational force of the earth on the ball is given by             $\text{W}\,\,\text{=}\,\,\text{F}\,\,\text{ }\!\!\times\!\!\text{ }\,\,\left( \text{-S} \right)\,\,\text{=}\,\,\text{-F}\,\,\text{ }\!\!\times\!\!\text{ }\,\,\text{S}$ Thus, work done by the force is negative.   Example:   A man lifts a luggage of 10 kg from the ground and puts it on his head 1.5 m above the ground. Calculate the work done by him on the luggage.   Solution: Mass of luggage, $m\,\,=\,\,10\,\,kg$             Displacement, $s\,\,=\,\,1.5\,\,m.$             Work done, $W\,\,=\,\,F\,\,\times \,\,S\,\,=\,\,mg\,\,\times \,\,S$             $=10\,\,kg\,\,\times \,\,10\,\,m\,\,{{s}^{-2}}\,\,\times \,\,1.5\,\,m$             $=\,\,150\,\,kg\,\,m\,\,{{s}^{-2}}\,\,m$             $=\,\,150\,\,N\,\,m\,\,=\,\,150\,\,J$             Work done is 150 J.          Energy Energy is the capacity or ability to do work. Without energy life is impossible. The demand of energy has been increasing very rapidly day by day. The sun is the biggest natural source of energy for us. The amount of energy possessed by a body is equal to the amount of work a body can do when its energy is released. Energy has magnitude only. Therefore, it is a scalar quantity. The S.I. unit of energy is joule, which is denoted by the letter J. The energy required to do 1J of work is called 1 J energy.   Forms of Energy There are different forms of energy. The two main forms of energy are kinetic energy and potential energy.   Kinetic Energy   Moving ball and a running boy possesses kinetic energy The energy of a body due to its motion is called kinetic energy. A moving object can do work. For example, moving bullet, rotating of a wheel, moving hammer, blowing wind, etch can do the work. In other words, we can say that every object around us which is moving posssesses kinetic energy. When a moving object is stopped by an opposite force, the kinetic energy is lost. The formula of kinetic energy is: Kinetic Energy  $=\,\,\frac{1}{2}\,\,\times \,\,m\,\,\times \,\,{{v}^{2}}$ Where: m = mass of an object in Kilograms v = speed of an more...

#### Atoms and Molecules

Atoms and Molecules   All the matters found in this universe are made up of small particles called atoms. Atoms combine to form molecule. Different atoms and molecules have different properties due to which different matters show different properties.   Laius of Chemical Combination            The laws of chemical combination are:
• Law of conservation of mass
• Law of constant proportions
Law of Conservation of Mass This law states that in a chemical reaction, the total mass of products is equal to the total mass of reactants. There occurs no change in mass during a chemical reaction. For example, in the following chemical reaction:   Sodium carbonate + ethanoic acid $\to$ sodium ethanoate + carbon dioxide + water   The addition of mass of sodium carbonate and ethanoic acid will be equal to the addition of mass of sodium ethanoate, carbon dioxide and water.   Law of Constant Proportions Law of constant proportions states that chemical compound always consists of the sameelements combined together in the same proportion by mass. For example, water is a chemicalrompound that is always composed of hydrogen and oxygen combined in the same constantproportion of 1:8 by mass.   Dalton’s Atomic Theory Dalton’s Atomic theory of matter states that all matter is made up of very small indivisible particles. Dalton gave his atomic theory of matter in 1805. The various postulates of Dalton’s atomic theory of matter are:   (i) Atoms can neither be created nor destroyed. (ii) Atoms are of various types. (iii) Atoms of different elements differ in mass, size and chemical properties. (iv) All the matter is made up of very small particles called atoms. (v) Atoms cannot be divided. (vi) All atoms of given element are identical, having same mass, size and chemical properties. (vii) The number and type of atoms in a given compound is fixed. (viii) Chemical combination between two or more elements consists in the joining together of atoms of these elements to form molecules of compounds. (ix) During chemical combination, atoms of different elements combine in small whole numbers to form compounds. (x) Atoms of the same elements can combine in more than one ratio to form more than one compound.   Limitations of Dalton’s Atomic Theory Some of the statements of Dalton's atomic theory are not correct. The following are the limitation of Dalton's atomic theory: (i) One of the main limitations of Dalton's atomic theory of matter is that atoms were thought to be indivisible. Now it is known that atoms can be divided into smaller particles called electrons, protons and neutrons.   (ii) Another limitation is that this theory assumes that all the atoms of an element have exactly the same mass. Now it is known that atoms of the same element can have slightly different masses. These atoms are called isotopes.   (iii) Another limitation is that this theory assumes that atoms of different elements have different masses. Now, it is known that more...

#### Cells and Tissues

Cells and Tissues   Cell The cell is the basic structural and functional unit of living organisms. All living organisms are composed of functional units called cells. The organisms can be of two types unicellular and multicellular. The unicellular organisms such as amoeba, paramecium has a single cell in their body and this single cell performs all basic life activities. The multicellular organisms such as human beings have millions of cells in their body. Most of these cells are specialised to carry out a few functions efficiently. A group of cells is responsible for performing a specific function. For example, muscle cells contract and relax to cause movement of a body part.   Structure of a Cell Different cells have different types of structures which depends on their specific functions. The size, shape, number and volume vary largely in multicellular and unicellular organisms. The size of the cell of bacteria is smallest and ostrich egg is largest. The volume of a cell is constant for a particular cell type and is independent of the size of the organism. For example, kidney or liver celles of a bull, horse and mouse are same in size. The number of cells depends on the types of organisms. It is indefinite in multicellular and definite in unicellular.             Plant Cell   Different parts of a cell and their functions: Plasma membrane - Outermost covering of the cell which allows only selective substances to pass through it.   Cytoplasm - Helps in exchange of materials between different cell organelles.   Endoplastic reticulum - helps in synthesis and transport of proteins and fats.   Mitochondria - Oxidises food to release energy in the from of ATP.   Golgi apparatus - Helps in storage of secretory products.   Ribosomes - Helps in protein synthesis.   Lysosome - Helps in intra-cellular digestion.   Nucleus - Helps in cell division and regulates all functions within the cell. Nucleolus - helps in protein synthesis by forming and storing RNA.   Vacuoles - helps in storage of water and other substances.        Difference Between Diffusion and Osmosis
Diffusion Osmosis
1. It is a process of movement of molecules or ions of a substance from a region of higher concentration to a region of their lower concentration. 1. It is the diffusion of water molecules from a dilute solution to a concentrated solution through a semi permeable membrane. more...

#### Matter in Our Surroundings

Matter in Our Surroundings   Matter Everything in this universe is made up of matter. Examples of matter are iron, wood, oil, kerosene, petrol, rock, minerals, water, air, coal, etc. Matters are classified on the basis of physical and chemical properties. On the basis of physical properties, matter is classified as solid, liquid and gas. On the basis of chemical properties, matter is classified as elements, compounds and mixtures. Matter is made up of particles.   Characteristics of Particles of Matter
• The various characteristics of particles of matter are:
• They are extremely small in size.
• They have spaces between them.
• They are constantly moving.
• They attract each other. The force of attraction between particles of same substance is known as cohesion. Particles of different matter exert different amount of force of attraction.
Classification of Matter on the Basis of Their Physical Properties On the basis of physical properties, all the matters are classified into three groups called solid, liquid and gas. In other words, we can say that matter exists in three physical states namely solid, liquid and gas.   States of Matter   States of Matter   The following are the properties of three states of matter:   Solid The various properties of solids are:
• They have fixed shape and fixed volume.
• They have closely packed particles. There is a strong force of attraction between the particles that holds them together in fixed position.
• They cannot be compressed.
• They have high density.
• They do not flow.
Stone (Solid) Liquid    The various properties of liquids are:
• They have fixed volume but not fixed shape.
• They cannot be compressed much.
• They have closely packed particles, but not as closely packed as in solids.
• They have moderate to high density. Liquids are usually less dense than solids. The force of attraction between the particles is strong enough to hold the particles together, but not strong enough to hold them in fixed position.
• They generally flow easily.
Water (liquid)   Gas The various properties of gases are:
• They neither have fixed shape nor fixed volume. Gases take the shape and volume of the container in which they are kept.
• They have particles that are much farther apart from one another as compared to solid and liquids. The force of attraction between particles of gas is negligible, therefore; the particles can freely move in any direction.
• They can be compressed easily.
• They have very low densities. Gases are very light in weight.
• They flow easily. They move from higher concentration to lower concentration and this movement is called diffusion.
Air (gas) filled balloon   Changing the State of Matter The three physical states of matter can be more...

#### Real Numbers

Real Numbers   In this chapter we will learn about real numbers. A real number can be any positive or negative numbers. All the rational and irrational numbers are real numbers. In other words we can say that real numbers are the set of rational and irrational numbers.   Important Points Related to Real Numbers
• A rational number is a real number which can be written as a simple fraction (i.e. in a ratio of two integers). In other words, a number r is called a rational number when it can be written in the form $\frac{p}{q}$ where p and q are integers and q is not equal to zero. For example $\frac{3}{5}$, 0, 3, $\frac{1}{100}$ are rational numbers.

• The decimal expansion of a rational number is either terminating or non-terminating recurring.
For example $\frac{12}{5}=2.4$ and $\frac{13}{9}=1.44444$…, are       decimal expansions of rational numbers.
• An irrational number is a real number which can not be written as a simple fraction. In other words, a number s is called an irrational number when it can not be written in the form $\frac{p}{q}$, where p and q are integers and q is not equal to zero.
For example,$\sqrt{2}$=1.41421356…., $\sqrt{3}=$1.732058075....,$\pi =$3.14159265...... are irrational numbers since they can not be written in the form $\frac{p}{q}$ Note: (i) We use $\pi =\frac{22}{7}$, which is its approximate value but not accurate. (ii) The decimal expansion of irrational number is non-terminating non-recurring. For example 1.002000200002 ...... is an irrational number.
• For any rational number rand irrational numbers, $r+s$, $r-s$are irrational numbers and for any non zero rational number r and irrational number s, r.s and $\frac{r}{s}$ are irrational numbers.
• When product of two irrational numbers is rational then each one of these factors is called the rationalizing factor of other.
For example, (i) $(a+\sqrt{b})\,\,and\,\,(a-\sqrt{b})$ (ii) $(a+b\sqrt{m})\,\,and\,\,(a-b\sqrt{m})$ (iii) $(\sqrt{m}+\sqrt{n})\,\,and\,\,(\sqrt{m}-\sqrt{n}$ Are rationalising factors of each other, where a and b are integers and m and n are natural numbers.
• For any two rational numbers a and b (when a$<$b), $\frac{a+b}{2}$is a rational number lying between a and b.
• For any two rational numbers a and b (when a $<$ b), n number of rational numbers
between a and b are, a + d, a + 2d, a + 3d,…., a + nd, where $d=\frac{a-b}{n+1}$   Some Results of Real Number For all positive real numbers a and b, (i) $\sqrt{ab}=\sqrt{a}\times \sqrt{b}$     (ii)$\sqrt{\frac{a}{b}}=\sqrt{\frac{a}{b}}$ (iii) $(\sqrt{a}+\sqrt{b})\,\,(\sqrt{a}-\sqrt{b})=a-b$ (iv) $(a+\sqrt{b)\,\,}(a-\sqrt{b})={{a}^{2}}-b$ (v) ${{(\sqrt{a}+\sqrt{b})}^{2}}=a+2\sqrt{ab}+b$   The Radical Sign and Radicand A radical expression is an expression of the type $\sqrt[n]{x}$. The sign ‘ $\sqrt[n]{{}}$’ is called the radical sign the number under this sign ie. ‘x’ is called the radicand and n is called the order of the $\sqrt{2}$,$\sqrt{3},$$\sqrt{4},$radical. For example etc. are radicals. Irrational radicals such as etc. $\sqrt{2}$,$\sqrt{3},$$\sqrt{4},$ are also known as surds.   Laws of Exponents for Real Numbers If and more...

#### Improvement in Food Resources

Improvement in Food Resources   Improvement in Food Resources Food is our basic need. From food we derive energy to do all activities. In the last few decades, the population of our country has increased manifold. To provide the food security to this growing population is really a onerous task. It is necessary that there should be an improvement in food resources so that we can provide the food security to our people. Our government has made efforts to meet the food demand by increasing food production. The efforts have brought successes up to a certain extent. The green revolution has increased the production of food grains manifold. The white revolution, has led to better and more efficient use as well as availability of milk. The above mentioned revolutions have led to the extensive use of our resources that cause imbalances. We need to follow the method of sustainable development to ensure the conservation of our natural resources. Food security can be provided to the common man through sustainable development.   Enhancement in Crop Yields To improve the crop yields, our government has taken many steps. The steps taken by the goveminent has brought fruitful result as well. The following are the steps taken to improve the crop yielding:   Crop production and management: Our country is an agricultural country where the large Population depends on the agriculture. Agricultural products are the sources of raw materials for industries. Thus, the proper crop production management is necessary, so that maximum benefit can be taken at the minimum cost. Govt has ensured the crop production management at various level.   Genetic manipulation of crops for higher yield: It is the incorporation of desirable character in the plants by various methods such as DNA recombinant technology, hybridisation, mutation, etc. In this process, a gene of one organism is inserted into the DNA of other organism and thus a new organism is born with better features.   Crop protection management: Crops are in danger because of the pests, insects, moisture, mites, rodents, bacteria, etc. There are various methods that are used to protect the crops from the possible danger. Insecticides, pesticides and weedicides are used to kill insects, pests and weeds. The following are the techniques that are used to protect the crop from possible dangers: Practice of crop rotation Right time of sowing seed Using high quality and resistant variety of seeds   Nutrient Management Nutrient is an important part of plant's food. Plants require nutrients for their growth that are supplied by air, water and soil. The nutrients required by the plants is categorised into two parts that are macro nutrients and micro nutrients. The deficiency of any nutrient in the plant body leads to diseases and affects the growth of the plant. There are natural ways to supply these nutrients to the plants but artificial ways are also used on a large scale to supply all the nutrients required by the plants in the form of more...

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