PSEB Notes

This PSEB 9th Class Social Science Notes Geography Chapter 2a India: Physiographic Units will help you in revision during exams.

PSEB 9th Class Social Science Notes Geography Chapter 2a India: Physiographic Units

→ The branch of science which studies the factors responsible for the formation of landscapes is known as Geomorphology.

→ India’s total landform is divided into plains (43%), mountains (29.3%), and plateau regions (27.7%).

→ According to’ to the surface, India can be divided into five parts:

• Himalaya mountain
• Northern Plains
• Plateau region
• Coastal plains
• Islands

→ Around1 12 crore years ago, there was a sea called ‘Tethys’ where presently Himalaya mountain is situated.

→ The highest mountain peak of the world is Mount Everest and of India is Godwin Austin (Kg).

→ Famous passes of the subcontinent are in the Himalayan region. Central Himalaya is famous for its hill stations.

→ Bhabhar, Terai, Bangar, Bhoor, etc. are different types of plains.

→ Bist Doab and Bari Doab are in India and Chaj Doab is in Pakistan.

→ The meaning of Sunderban is the forest full of Sunderi trees.

→ Plateau of Central India, Malwa Plateau, and Southern Plateau are the plateau regions of India. These are the parts of the peninsular plateau.

→ Thai ghat, Bhor ghat, and Pal ghat are the famous passes of western ghats.

→ The plateau region of eastern ghats is full of minerals.

→ Kutch, Konkan, Malabar, Coromandel, and Northern Circars are the parts of Coastal plains.

→ There are around 267 islands in the Indian island groups.

→ They can be divided into two groups-Andaman-Nicobar islands in the Bay of Bengal and the Lakshadweep islands in the Arabian Sea.

→ Malwa plateau is triangular in shape.

→ Chota Nagpur plateau is famous for minerals and is a part of the Malwa plateau.

This PSEB 9th Class Social Science Notes Geography Chapter 1b Punjab: Size and Location will help you in revision during exams.

PSEB 9th Class Social Science Notes Geography Chapter 1b Punjab: Size and Location

→ Punjab is considered the creator of Indian history and civilisation.

→ It was the birthplace of Harappa and Indus valley civilisation which was one of the most famous ancient civilisations of the world.

→ With the Indian partition in 1947, Punjab was also divided. Indian Punjab was called eastern Punjab.

→ Due to the partition, most of its fertile land went over to Pakistan. Only 34% of its total land remained in India.

→ In the formation of Punjab’s civilisation, Aryans, Greeks, Kushanas, Mughals, and Afghans played a very important role.

→ The ancient names of Punjab were Saptsindu, Panjnad, Lahore Suba, Pentapotamia, Tak Pradesh, etc.

→ Present Punjab is only 20% of undivided Punjab.

→ From 1948 to 1956, many of Punjab’s areas were included in the PEPSU area.

→ There are 5 administrative divisions, 22 districts, 91 Tehsils, and 150 blocks in Punjab.

→ Pathankot is the smallest district of Punjab.

→ The ancient names of Ravi, Beas, and Satluj were Purushvi, Vipasha, and Satudari respectively.

→ Kapurthala, Patiala, Sangrur, Nabha, and Malerkotla were principality cities of Punjab.

→ Ludhiana district touches the boundaries of seven districts of Punjab.

This PSEB 9th Class Social Science Notes Geography Chapter 1a India: Size and Location will help you in revision during exams.

PSEB 9th Class Social Science Notes Geography Chapter 1a India: Size and Location

→ India is a vast country. Geographically, India is the seventh-largest country in the world.

→ From the point of view of the population, after China, India is the second-largest country.

→ The extension of Himalaya mountain and sea from three sides gives India the status of Sub-continent.

→ India has 2.4% of the total land of the world.

→ India’s north-south extension is 3214 km. and the east-west extension is 2933 km. 82°30′ East is considered the standard meridian of India. Its time is 5 hours 30 minutes ahead of Greenwich’s meantime.

→ When the meridian of any country is taken as its standard meridian, its time is known as the standard time.

→ A subcontinent is a vast independent geographical unit.

→ This landmass is distinctly separated from the main continent.

→ Indian boundary touches the boundary of seven countries.

→ India has a land boundary of about 15,200 km and a total coastline of about 7516 km.

→ The meaning of SAARC is South Asian Association for Regional Co-operation.

→ India keeps the most important position among other SAARC nations.

→ India has 28 states and 8 union territories.

→ Delhi is National Capital Region (NCR). Its capital New Delhi is the capital of the country.

→ Chandigarh (Punjab, Haryana) and Hyderabad (Andhra Pradesh, Telangana) are the two cities that are the capitals of more than one state.

→ India’s eminent position in the Indian Ocean creates a quite favourable environment for international trade.

This PSEB 9th Class Science Notes Chapter 15 Improvement in Food Resources will help you in revision during exams.

PSEB 9th Class Science Notes Chapter 15 Improvement in Food Resources

→ Food is the basic requirement of all organisms for their survival.

→ Food supplies nutrients like proteins, carbohydrates, fats, vitamins, and minerals to our bodies.

→ Human beings are dependent on animals and plants for food.

→ Human beings obtain most of this food from plants and animals.

→ Therefore, it is necessary to increase production efficiency for both crops and animals (Livestock, Poultry, Fishes, Honeybees).

→ Plants provide food like cereals, pulses, oilseeds, fruits, and vegetables.

→ Animals provide milk and milk products, meat, eggs, honey, etc.

→ Agriculture is the largest industry in India, engaging about 70 percent of our population.

→ The sustainability of agriculture can be achieved by adopting various techniques such as mixed cropping, crop rotation, and crop improvement.

→ Sustainable agriculture is the successful management of resources for agriculture to satisfy the changing human needs while maintaining or enhancing the quality of the environment and conserving natural resources.

→ Mixed cropping is the practice of cultivating more than one crop, that is, growing two or more crops, simultaneously in the same field.

→ In the agroforestry system, crops are grown alongwith trees.

→ The practice of growing different types of crops alternately in the same field is called crop rotation.

→ 16 nutrients are essentially required, four are required in large quantities and are known as macronutrients whereas nine nutrients required in small quantities are known as micronutrients.

→ Manures and fertilizers are the main sources of nutrients supplied to plants.

→ Manures increase soil fertility.

→ Fertilizers are commercially manufactured materials from chemicals.

→ Fertilizers increase the yield of crops.

→ Insect pests and diseases can cause 50-70 percent damage to crops.

→ Weeds are unwanted plants that grow in fields.

→ Mineral or chemical fertilizers contain inorganic chemical substances like nitrates, phosphates, potassium, etc.

→ Chemical fertilizers are required in smaller bulk.

→ Chemical fertilizers are expensive.

→ Compost manure mainly consists of rotten vegetables and animal refuse.

→ Biofertilizers are organisms that bring about soil nutrient enrichment.

→ Soil water acts as a medium for the conveyance of salts needed in plant nutrition.

→ Breakthrough in cereal production due to the use of high-yielding varieties, higher dose of fertilisers, and irrigation is known as the green revolution.

→ Varietal improvement is required for higher yield, good quality, and changing situations.

→ Storage losses in agricultural production may be quite high due to the following biotic and abiotic factors:

• Insects
• Rodents
• Fungi
• Mites
• Bacteria

→ Abiotic factors include excess moisture and inappropriate temperature.

→ These factors cause degradation in quality, loss in weight, poor germinability, and discoloration of produce.

→ Proper drying and fumigation using chemicals that can kill pests are some of the preventive measures.

→ Animal husbandry is the science of rearing, caring, breeding, and utilization of animals.

→ The main aim of animal husbandry is to provide proper food, water, and good shelter to animals.

→ It also involves protecting them from diseases, and their breeding for its best economic use.

→ Cows, buffaloes, fowl, fish, goats, and sheep are useful animals. They provide us food i.e., milk, egg, wool, and meat (fowl and goat).

→ Milk contains all nutrients such as carbohydrates, protein, fats, vitamins, and minerals.

→ Breeds of cattle are divided into three categories: Milch breeds (provide milk e.g. Gir, Sahiwal, Red Sindhi, etc.); draught breeds (used as work animals e.g. Malvi, Hallikar, etc.) and dual-purpose breeds (e.g. Haryana, Deoni, Tharparkar, etc.)

→ Important indigenous breeds of buffaloes are Red Sindhi, Sahiwal, Murrah, Mehsana, Surti, Nili Ravi, etc.

→ Important exotic breeds of milch cows are Holstein and Friesian (Holland), Jersey (USA), Brown-Swiss (Switzerland), etc.

→ Exotic breeds of cows have a longer lactation period and more average annual milk production than those of indigenous breeds.

→ High milk-yielding cross-breeds of cows are Karan-Swiss, Karan-Fries, Frieswal, etc. These have been developed at NDRI Kamal. Kamal-Swiss is a crossbreed of Sahiwal and Brown Swiss.

→ Two main components of cattle feed are roughage (fiber-rich but with low nutrients) and concentrate (rich in proteins, palatable, and easily digestible).

→ A good shelter improves the health and yield of animals.

→ Animal Feed: It means food provided to the animal, which are of two types:

• Roughage: It is a coarse and fibrous food with low nutrition, such as green fodder, silage, hay, and legumes.
• Concentrates: These are the substances that are rich in one or more nutrients. Cotton seeds, oil seeds, oil cakes, and some cereals like gram and bajra are some typical concentrates.

→ Breeding of cattle is done in two ways natural and artificial.

→ Egg production in chicken: Egg production is the most economic trait.

→ A layer hen starts laying eggs at the age of 20 weeks. The egg production period in a commercial layer is 500 days.

→ For increasing the egg production for the development of new variety with respect to quantity and quality of eggs, the following points are to be considered:

• Egg number
• Sexual maturity
• Egg weight
• Bodyweight
• Feed efficiency
• Egg size
• Egg shape
• Shell colour
• Shell quality
• The internal quality of egg

→ Poultry farming provides meat, eggs, and manure (poultry waste).

→ Poultry farming is raising domestic fowls, ducks, geese, turkeys, pigeons etc. Poultry production includes egg production and broiler production for poultry meat.

→ To enhance poultry production, crossbreeding is done between Indian and exotic breeds for variety improvement.

→ Fishes may be obtained from seas i.e. marine resources and rivers, lakes i.e. inland resources.

→ To increase production of a choice variety of fishes can be cultured in marine and inland ecosystems.

→ Fishes are caught by fishing nets and gears operated from fishing vessels having modern devices such as echo-sounders and navigational gadgets.

→ In freshwater, the induced breeding technique is very useful in obtaining quality fish seeds in large quantities.

→ A composite fish culture system is used commonly to produce table fish.

→ Fisheries are composed of finfishes (true fishes) and shellfish include prawns, mollusks, etc.

→ Beekeeping is done to get honey and wax.

→ The honey flow period is the total time period in which bees collect nectar and pollen.

→ Macronutrients: The mineral nutrients needed by plants in large amounts are called macronutrients e.g. Nitrogen, Phosphorus, Calcium.

→ Micronutrients: The mineral elements needed by plants in very small amounts e.g. Boron, Zinc, Copper.

→ Farm Yard Manure (FYM): Livestock farm waste i.e. cattle excreta (cow dung and urine) is stored in a pit for decomposition. After 1-2 months this is used as FYM in farming practices.

→ Compost: The process in which waste material like vegetable waste, animals refuse, domestic waste, sewage waste, straw, eradicated weeds, etc. is decomposed in pits and is known as composting. The compost is rich in organic matter and nutrients.

→ Green Manure: In the cultivation field prior to the sowing of the seeds, some crops like sun hemp, guar, etc. are grown. After some time these plants are mulched by ploughing. These green plants thus turn into green manures which helps in enriching the soil by N and P.

→ Insecticides: Chemicals that kill insects.

→ Manures: Manures are the organic substances obtained from the decomposition of vegetable and animal wastes by the action of microorganisms.

→ Weeds: The small-sized unwanted plants which grow along with a cultivated crop in a field are called weeds.

→ Weedicides: Chemicals that destroy weeds are called weedicides.

→ Humus: Manures provide humus to the soil. Humus improves the physical and chemical texture of the soil.

→ Mixed cropping is the practice of cultivating more than one crop, that is, growing two or more crops, simultaneously in the same field.

→ Crop rotation: The practice of growing different types of crops alternately in the same field is called crop rotation.

→ Animal husbandry: Science of rearing, feeding, caring, and breeding of animals.

→ Roughage: It is a coarse and fibrous food with low nutrition, such as green fodder, silage, hay, and legumes.

→ Concentrates: These are the substances that are rich in one or more nutrients. Cotton seeds, oil seeds, oil cakes, and some cereals like gram and bajra are some typical concentrates.

→ Poultry: Rearing of birds to increase the yield of meat and eggs.

→ Livestock: Domesticated animals like cattle, sheep, goats, camels, horses, pigs, etc.

→ Pisciculture: Pisciculture is the rearing and breeding of fish by a man in ponds, tanks, and artificial reservoirs.

→ Artificial insemination: Introducing the semen of a fertile male into the vagina of a fertile female.

This PSEB 9th Class Science Notes Chapter 14 Natural Resources will help you in revision during exams.

PSEB 9th Class Science Notes Chapter 14 Natural Resources

→ Earth is the only planet on which life exists.

→ Life on earth depends upon ambient temperature, water, and food.

→ The resources on earth are equally important.

→ The most important requirement is solar energy.

→ The environment is the surroundings of an organism and influences its life.
or
The environment is the sum total of all the components both from living and non-living ones.

→ The living or biotic components include plants, animals, and microorganisms whereas non-living or abiotic or physical components consists of air, water, soil, light, and temperature.

→ The habitat of plants and animals greatly varies.

→ Natural resources. It is the stock of nature such as air, water, soil, coal, minerals, animals, and plants that are useful to mankind in many ways.

→ Life on earth depends upon resources like soil, water, air, and energy from the sun. Inexhaustible resources are present in plenty and cannot be exhausted by man’s consumption.

→ The stock of exhaustible natural resources in nature is limited and will finish sooner or later.

→ Air is an important form of inexhaustible natural resource which is essential for our survival.

→ Composition of Air:

• Nitrogen (N₂) – 78%
• Oxygen (O₂) – 21%
• Carbon dioxide (CO₂) – 0.03%
• Argon – 0.93%
• Helium, Neon, Ozone, Ammonia – 0.04%

→ Helium, Argon, and Neon are noble gases.

→ Lithosphere: It is the outer crust of our planet, the Earth.

→ Hydrosphere: It is the portion of the earth’s surface covered with water which is about 75 percent—comprising of seas, oceans, rivers, streams, lakes, ponds, etc.

→ Atmosphere: It is the multilayered gaseous envelope of air that covers the whole of our planet Earth like a blanket.

→ Atmosphere plays important role in the control of climate, movement of air (winds), and rain.

→ Biosphere: It is the life-supporting zone of the Earth where the atmosphere, the hydrosphere, and the lithosphere interact and make life possible.

→ It occupies the highest position or level in the hierarchy of organisation on the earth.

→ Water is an important medium for all the life processes and acts as a universal solvent and is termed ‘wonder liquid’.

→ Water covers 75% of the earth’s surface.

→ The oceans, rivers, streams, lakes, ponds, pools, polar ice caps, water vapours constitute the hydrosphere.

→ Soil is another main natural resource essential for our survival and development.

→ Soil forms the upper surface of the land and supports plant growth.

→ Soil is an important resource that decides the diversity of life in an area.

→ The outermost layer of Earth is called the crust and the minerals found in this layer supply a variety of nutrients to life forms.

→ Causes of Soil Erosion:

• Wind causes soil erosion by carrying away the top loose soil particles.
• Rain causes soil erosion on unprotected topsoil by washing it down.
• Improper farming or tilling and leaving the field fallow for a long time causes soil erosion.
• Frequent flooding of rivers causes soil erosion by removing the fertile topsoil of the fields near the river banks.
• Deforestation also leads to soil erosion.

→ The underground reservoir of the earth of metals and minerals is limited.

→ Renewable sources of energy are regenerated naturally within a short span of time e.g. plants, animals, sunlight, etc.

→ Non-renewable sources of energy take millions of years to form like coal, lignite, petroleum, and natural gas.

→ The substances like water, oxygen, carbon, and nitrogen move from one stage to another say from biotic to abiotic and again to biotic components in a cyclic manner.

→ Air Pollution: It is an undesirable change in the physical, chemical, or biological characteristics of air. It is caused due to an increase in the content of harmful substances (air pollutants) in the air such as oxides of nitrogen and sulphur, etc.

→ The major sources of air pollution are the burning of fossil fuels like coal and petroleum, automobiles, thermal power plants, and industries.

→ Pollution of air, water, and soil affects the quality of life and harms biodiversity.

→ Water Pollution is the contamination of the water of rivers and lakes with unwanted and harmful substances.

→ Water is said to be polluted when there is any physical, biological, or chemical change in its quality that adversely affects living organisms and makes it unfit for use.

→ The balance in the environment including the flow of energy and matters is also supported by various living beings by acting as producers and consumers.

→ Forests provide timber for building and furniture along with raw materials for the paper industry.

→ Ozone layer: Ozone is a triatomic gas with a molecular formula O3 which is present in the upper reaches of the atmosphere (in the stratosphere region).

→ The ozone layer prevents the harmful radiations of the sun from reaching the surface of the earth, where they may damage many forms of life.

→ Role of ozone: Unlike oxygen, ozone is poisonous but it performs a very important role for us.

→ It forms a thick layer in the upper regions of the atmosphere and absorbs harmful radiation from the sun.

→ This prevents those harmful radiations from reaching the surface of the Earth where they may damage many forms of life.

→ CO₂ forms 95-97% of the atmosphere on Venus and Mars.

→ On the moon, the temperature ranges from -190°C to 110°C.

→ Smog formed by smoke and fog is a visible indication of air pollution.

→ Exhaustible Resources: These resources are limited in nature and will finish sooner or later.

→ Inexhaustible resources: These resources are unlimited and cannot be exhausted by man’s consumption.

→ Renewable resources: These resources are naturally replenished after man’s consumption.

→ Non-Renewable Resources: These resources cannot be replaced after they are used.

→ Underground Water: The water present below the soil is called underground water.

→ Crust: Topmost surface of the earth is called the crust.

→ Mineral resources: These resources are present on earth and are non-renewable.

→ Atmosphere: It is a transparent gaseous envelope surrounding the earth.

→ Pollution: It is an undesirable change in physical, chemical, or biological characteristics of the water and soil.

→ Acid rain: When gases like SO₂ and SO₃ react with water to form sulphuric acid and sulphurous acid and precipitate as rain is called acid rain.

→ Smoke: It is a secondary pollutant produced as a result of reactions of products of incomplete combustion.

→ Smog: Combination of smoke and fog forms smog (Smoke + fog = Smog).

→ Aerosoles: Certain chemicals are released in the air with force in the form of mist or vapour.

→ Soil: The topmost fertile layer of the earth capable of supporting plant growth is called soil.

→ Fertility of soil: The capacity of the soil to sustain plant life with required nutrients is called the fertility of the soil.

→ Water covers 75% of the earth’s surface.

→ NGO: Non-Governmental Organisation.

→ IUCN: International Union For Conservation of Nature and Natural Resources.

This PSEB 9th Class Science Notes Chapter 13 Why Do We Fall Ill will help you in revision during exams.

PSEB 9th Class Science Notes Chapter 13 Why Do We Fall Ill

→ According to WHO, health is a state of complete physical, mental and social well-being, and not merely an absence of disease or infirmity.

→ Health is a state of being well enough to function well physically, mentally, and socially.

→ Good health is characterized by – the absence of disease, free from social and psychological tensions, self-confidence, and efficient working.

→ Good health brings all-around progress and is the real wealth of an individual.

→ Good health is adversely affected by – overpopulation, environmental pollution, poverty, ignorance, unhealthy sexual life, etc.

→ Personal health includes four aspects: Personal cleanliness, exercise, rest, and healthy habits.

→ Basic conditions for maintaining good health are a Balanced diet; proper habits; exercise and relaxation habits, clean food, air, and water; avoiding hazardous substances; proper education, etc.

→ Different organs of different systems show interactions and interdependence.

→ The supply of food is a must for the proper functioning of organs to keep a person healthy.

→ Diseases are classified as acute or chronic, depending on their duration.

→ The disease may be due to infectious or non-infectious causes.

→ Infectious agents belong to different categories of organisms and may be unicellular and microscopic or multicellular.

→ On the basis of period of occurrence, diseases are of two types: Congenital (inborn diseases e.g. Haemophilia, Albinism) and acquired (during one’s own life span) diseases.

→ Acquired diseases are of two types on the basis of their communication: Communicable (which can be transmitted from diseased person to healthy persons) and Non-communicable diseases.

→ Communicable diseases are also called infectious diseases as these occur due to successful infection of the pathogenic (disease-causing) micro-organisms.

→ Infectious diseases can be prevented by public health hygiene measures that reduce exposure to infectious agents.

→ Common examples of diseases caused by viruses are common cold, influenza, dengue fever, and AIDS.

→ Typhoid fever, T.B., cholera, and anthrax are caused by bacteria.

→ Skin infections are caused by fungi.

→ Malaria, Kala Azar, sleeping sickness are caused by protozoans.

→ Ascariasis and elephantiasis are caused by worms.

→ AIDS, Syphilis, and Gonorrhoea are sexually transmitted diseases.

→ Principles of Prevention: Following three limitations are normally confronted while treating an infectious disease:

• If a person has a disease, his/her body functions are damaged and may never recover completely.
• Treatment will take time, which means that person suffering from a disease is likely to be bedridden for some time even if given proper treatment.
• The person suffering from an infectious disease can serve as the source from where the infection may spread to other people.
• It is because of such reasons that the prevention of diseases is better than their cure.

→ Some common vaccines:

• DPT vaccine for protection against diphtheria, whooping cough, and tetanus.
• BCG vaccine for protection against tuberculosis.
• Polio (OPV) vaccine.
• Typhoid vaccine.
• Measles vaccine.
• TT vaccine against tetanus.
• Hepatitis A and Hepatitis B for protection against jaundice.

→ Pulse Polio is an immunization campaign established by the Government of India in 1994 to eradicate poliomyelitis (polio) in India by vaccinating annually all children under age five against polio.

→ These vaccines form the public health program of childhood immunization for preventing infectious diseases.

→ Infectious diseases can also be prevented by using immunisation.

→ Effective prevention of infectious diseases in the community requires that everyone should have access to public hygiene and immunisation.

→ Vaccine against Hepatitis A is also available in our country.

→ August 20 is observed as ‘Malaria Day’.

→ December 1 is observed as ‘World AIDS Day’.

→ March 24 is observed as ‘World TB Day’.

→ The incidence of diarrhoeal disease is highest in Andhra and Orissa states.

→ Helicobacter pylori are responsible for peptic ulcers.

→ Bacteria Staphylococcus can cause acne.

→ Trypanosoma, a protozoan organism can cause sleeping sickness.

→ Health: It is a state of physical, mental, and social well-being.

→ Acute disease: Diseases that occur very rapidly, but occur for short period.

→ Chronic diseases: Diseases that last for long period and cause prolonged poor health.

→ Communicable diseases: These are transmitted from one man to another. These diseases are caused by viruses, Bacteria, Protozoa, Fungi, and Worms.

→ Non-Communicable diseases: The diseases which are not transmitted from an infected person to the other are called non-communicable diseases.

→ Antibodies: These are proteinic substances produced by the body in response to antigens and protect the body from damage.

→ Malnutrition: Defective nutrition due to inadequate intake of nutrients or due to faulty digestion or absorption or metabolism.

→ Allergy: Hypersensitive condition of the body in response to certain substances is termed allergy.

→ Disease: Any condition which interferes with the normal functioning of the body.

→ Acquired diseases: Diseases developed during own life span.

→ Congenital diseases: Inborn diseases which occur from birth.

→ Vaccination: A preventive inoculation that prevents the occurrence of disease by stimulating the immune system.

→ Therapy: Treatment of diseases.

This PSEB 9th Class Science Notes Chapter 12 Sound will help you in revision during exams.

PSEB 9th Class Science Notes Chapter 12 Sound

→ Sound is a kind of energy that produces a sensation of hearing in our ears.

→ Sound is produced due to vibrations of an object, Vibration means the to and fro movement of an object.

→ In human voice, the sound is produced due to the vibration of the larynx.

→ The substance through which sound travels is called medium.

→ Wave is a sort of disturbance.

→ For transmission of sound, a medium is required and the air is generally used as a medium.

→ Sound can not travel through a vacuum.

→ In transverse waves, the particles of the medium vibrate in a direction perpendicular to the direction of propagation of the wave.

→ The distance between two consecutive rarefactions is called wavelength.

→ The movement of compressions passing through a point in a unit of time is called frequency.

→ The time taken by two consecutive compressions or rarefactions passing through a fixed point is called the frequency of the wave.

→ The relation between velocity (υ), frequency (ν) and wavelength (λ) of the wave is υ = ν × λ

→ The velocity sound depends mainly upon the nature of medium and temperature.

→ To hear an echo the minimum time elapsed between the original sound and reflected sound should be 0.1 seconds.

→ Sound energy passing through a unit area in 1 second is called the intensity of sound.

→ The human audible range is 20 Hz to 20 kHz.

→ Sound travels through a substance in the form of longitudinal waves.

→ Sound travels through air medium in the form of compressions and rarefactions.

→ Compression is a region of high pressure and maximum density.

→ Sound: It is a kind of energy that produces in us the sensation of hearing.

→ Amplitude: The maximum displacement of the particle of the medium on either side of its mean position during vibration is called its Amplitude.

→ Frequency: The number of vibrations made by the vibrating body in 1 second is called its frequency.

→ Wavelength: Whatever time is taken by the particle to complete 1 vibration during the same time the distance travelled by the wave is called wavelength. It is denoted by ‘λ’.

→ Wave velocity: In a medium, the magnitude of the product of frequency and wavelength of a wave is equal to wave velocity i.e. υ = ν × λ

→ Oscillation or Vibration: The to and fro motion of a vibrating particle about its mean position to complete 1 vibration is called oscillation or vibration.

→ Periodic motion: The motion which is repeated after a fixed interval of time is called periodic motion,

→ Rarefaction: In longitudinal waves, the region where the particles of the medium are farther apart than the normal distance is called rarefaction. Here the pressure is lower than normal.

→ Echo: The reflected sound is called echo.

→ Transverse waves: Those waves in which the particles of the medium vibrate about their mean position in a direction perpendicular to the direction of propagation of the wave, such waves are called transverse waves.

→ Longitudinal waves: Those waves in which the particles of the medium vibrate forward and backward in the same direction in which the wave travels then the wave is called a longitudinal wave.

→ Ultrasonic waves: Those longitudinal waves which have a frequency of more than 20000 Hertz (Hz) are called ultrasonic waves.

→ SONAR (Sound Navigation and Ranging): It is a device that measures the time for producing sound waves and reflected waves.

→ Time Period: The time taken to complete one complete vibration (i.e. to travel from mean position to one extreme position than to other extreme position and back is called time period. It is denoted by ‘T’ and expressed in seconds.

→ Compression: Due to the forwarding motion of the longitudinal wave, the region where the particles of medium come close to each other than the normal distance between them is called compression. Here the pressure is higher than normal.

This PSEB 9th Class Science Notes Chapter 11 Work, Energy and Power will help you in revision during exams.

PSEB 9th Class Science Notes Chapter 11 Work, Energy and Power

→ All living beings need food for their energy needs.

→ Machines too need fuels like petrol and diesel for energy.

→ In our daily life, we consider any useful physical or mental activity as work.

→ Work done by the force acting on a body is equal to the product of the magnitude of the force and the displacement in the direction of the force.

→ When a force acts in a direction opposite to the direction of displacement produced, then the work done is negative.

→ When a force acts in the direction of displacement then the work done is positive.

→ For us, the sun is the major natural source of energy.

→ In addition to this, we can also get energy from nuclei of atoms, from the interior of earth, and tides.

→ If a body has the capacity to do work then it is said to possess energy.

→ The object which does work loses energy and the object on which work is done gains energy.

→ The sum total of potential and kinetic energy of the body is called mechanical energy.

→ The energy present in the body due to its motion is called it’s kinetic energy.

→ The kinetic energy of an object increases with the increase of its velocity.

→ When an object is raised to some height above the ground, the work done against gravitational force is stored in the object as potential energy.

→ We can transform one form of energy into another form.

→ The rate of doing work or transformation of energy is called power.

→ The unit of energy is joule but this unit is small. Its bigger unit is kilowatt hour (kWh) 1 kWh = 3.6 × 106 J

→ HP Energy consumed in industries and commercial establishments are expressed in kilowatt-hour which is also called unit (B.O.T. unit)

→ In order to survive all living beings have to do some basic activities for which energy is required. This energy they get from the food they eat.

→ According to the law of conservation of energy, energy can neither be created nor destroyed but it can only be transformed from one form to another form total energy before and after transformation always remains constant.

→ Energy is present in different forms as for example kinetic energy, potential energy, heat energy, chemical energy, electric energy, and light energy.

→ From a scientific point of view for doing work two conditions must be satisfied:

• some force must act on the object
• the object must be displaced in the direction of the force.

→ The unit of power is the watt.

→ 1 kilowatt = 1000 watt.

→ 1 watt is the power of that agent which does 1 joule of work in 1 second.

→ Energy: The capacity of doing work is called energy.

→ Kinetic Energy: The capacity of the bodies to do work due to the motion present in them is called kinetic energy.

→ Potential Energy: The capacity of an object to do work clue to change in its position or configuration is called its potential energy.

→ Law of Conservation of Energy: Energy can neither be created nor destroyed but it can be changed from one form into another form.

→ Joule: If one Newton (N) of force acts on a body of 1 kg and displaces it through 1 m then work done on the body is one joule.

→ Power: The rate at which energy is supplied or consumed is called power. The unit of power is the watt (W).
Power = \(\frac{\text { Energy Supplied }}{\text { Time }}\)

→ Watt: If a source supplies or consumes energy at the rate of 1 Joule (J) per second then the power of the source, is said to be one watt.

→ Work: If the force acting on a body displaces the body in the direction of force then work is said to be done by the force.
Work = Force × Displacement
i.e. W = F × S

This PSEB 9th Class Science Notes Chapter 10 Gravitation will help you in revision during exams.

PSEB 9th Class Science Notes Chapter 10 Gravitation

→ Everybody in this universe attracts every other body towards it with a force called Force of Gravitation.

→ The revolution of the moon around the earth and the falling down of a body projected upward is due to the force of gravitation.

→ Gravitation is a weak force unless it may not involve bodies having greater masses. The attractive force due to earth is called the force of gravity.

→ The law of gravitation is a universal law which means that this law applies to all big and small objects.

→ The magnitude of the force acting between the earth and the objects lying on the surface of the earth is given by formula F = \(\frac{\mathrm{GM} m}{d^{2}}\) where G = 6.673 × 10^-11 N-m²/kg²

→ The acceleration produced in the body due to the force of gravity is called acceleration due to gravity. It is denoted by ‘g’.

→ The value of ‘g’ is more on the poles than on the equatorial line.

→ The Force of gravity decreases with the increase of height above the surface of the earth.

→ The quantity of matter present in a body is called the mass of the body.

→ Mass is the measure of inertia of the body.

→ The mass of a body remains constant at all places.

→ The weight of a body is the force with which the body is attracted towards the centre of the earth.

→ The weight of an object depends upon the product of its mass (m) and the acceleration due to gravity (g). i.e. Weight (W) = mass (m) × acceleration due to gravity (g)

→ Force acting perpendicular to the surface of an object is called thrust.

→ Thrust acting per unit area is called pressure.
∴ Pressure = \(\frac {Thrust}{Area}\)

→ SI unit of pressure is Nm^-2 (or N/m²) or pascal (Pa).

→ The pressure exerted on an enclosed liquid is transmitted equally in all directions.

→ All bodies when immersed in liquid experience an upward force called upthrust or buoyant force.

→ The value of Buoyant force depends upon the density of the liquid.

→ If the weight of an immersed body is more than the upthrust then the body sinks in the liquid.

→ Those bodies float which has a density less than the density of the liquid in which they are immersed.

→ Those bodies, which have a density more than the density of the liquid in which it is immersed sink.

→ Archimedes’ principle states that when a solid body is wholly or partly immersed in a liquid then the body experiences an upward thrust due to liquid displaced by the immersed part of the body.

→ Relative density of a substance is defined as the ratio of the density of the substance to the density of the Same volume of water.
∴ Relative density = \(\frac {Density of substance}{Density of water}\)

→ Relative density has no unit.

→ According to Archimedes’ principle when a solid body is completely or partially immersed in a liquid and the weight of the body is equal to the weight of the liquid displaced by the immersed part of the body then the body floats.

→ Kepler gave the following three laws which govern the motion of the planets:

• The planetary path of each planet is elliptical at the centre of which the sun is situated.
• The line joining sun and the planet sweeps equal areas in equal intervals of time.
• The cube of the average distance ‘r’ of a planet from the sun is inversely proportional to the square of the orbital period ‘T’ of that planet.

→ Law of gravitation states that the force of attraction between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres. This force always acts along the line joining the centres of two objects.

→ Force of Gravitation: It is that force with which two bodies attract each other but they are lying apart.

→ Acceleration due to Gravity: Acceleration produced in the bodies falling freely under the action of gravity is called acceleration due to gravity.

→ Force of Gravity: It is the force with which earth attracts all bodies towards its centre.

→ Weight: The force with which the earth attracts bodies towards it is called weight.

→ Mass: The quantity of matter contained in the body is called it’s mass.

→ Inertial Mass: This mass measures the resistance which is produced due to a change in the position of rest or motion.

→ Universal Gravitational Constant: It is the force that acts between two bodies each of unit mass and lying unit distance apart.

→ Kepler’s first law: All planets move around the sun in elliptical orbits.

→ Kepler’s second law: The line joining planet and sun sweeps out equal area in equal intervals of time.

→ Kepler’s third law: Cube of mean distance ‘r’ of the planet from the sun is proportional to the square of its orbital period.

→ Thrust: The total force acting perpendicular to the surface of the body is called thrust.

→ Buoyant Force: The upward thrust applied by the liquid on the immersed body is called Buoyant force.

→ Pressure: Thrust acting per unit area of the surface in contact is called pressure.

→ Density: Mass per unit volume of the substance is called the density of the substance or it is termed as the ratio of the mass of a body to its volume.

• Density = \(\frac {Mass of the body}{Volume of the body}\)
• SI unit of density is kg/m³.

→ Relative Density: Relative density of a substance is defined as the ratio of the density of the substance to the density of the same volume of water. Since it is the ratio of two similar quantities, therefore it is only a number. It is also called the specific gravity of the substance.

→ Archimedes Principle: This principle states that whenever a solid body is immersed in a liquid either wholly or partly then it experiences an upward thrust due to the displaced liquid.

→ The universal law of Gravitation: The mutual force of attraction between every two bodies in this universe is directly proportional to the product of the masses of the two bodies and inversely proportional to the square of the distance between them. This force acts along the line joining the centres of the two bodies.

This PSEB 9th Class Science Notes Chapter 9 Force and Laws of Motion will help you in revision during exams.

PSEB 9th Class Science Notes Chapter 9 Force and Laws of Motion

→ Gallileo and Isac Newton put forth the scientific basis with regard to the motion of the objects.

→ The concept of force is based on the activity of pull, push or hit/kick.

→ By the application of force, the size and shape of an object can be changed.

→ Force is of two types:

• Balanced force
• Unbalanced force

→ An unbalanced force acting on an object produces motion in the object.

→ The frictional force acts against the direction of motion of an object.

→ The first law of motion is also called the Laws of Inertia.

→ The tendency of the body to remain in the state of rest or of uniform motion is called Inertia.

→ Everybody opposes the change in its state of motion.

→ The moment of inertia of the train is more than that of the cart so that it does not get displaced on being pushed. In other words, the heavier bodies have more inertia.

→ The inertia of an object is the measure of its mass.

→ The momentum ‘p’ of an object is measured by the product of its mass ‘m’ and velocity ‘v’. i.e. p = m × v

→ The momentum has both magnitude and velocity. Its direction is the same as that of velocity.

→ The S.I. unit of momentum is kg ms.

→ Force changes the momentum of an object.

→ To reduce the effect of friction the surface is either made plane or the surface is painted with a lubricant.

→ S.I. unit of force is the newton.

→ For the motion of the object due to the force acting on it, Newton gave three fundamental laws of motion which hold good for all types of motion.

→ According to the first law, everybody tends to remain in its state of rest or of uniform motion unless some external force acts on it.

→ According to the second law, the rate of change of momentum of a body is directly proportional to the unbalanced force acting on it and in its direction.

→ According to the third law, when one body applies force on another body, the second body also applies instantaneous force on the first body. These two forces are equal in magnitude but opposite in direction.

→ By applying force the motion can be given to a body at rest and the body in motion can be brought to rest or a change can be brought about in the same direction.

→ Force: It is an external cause that produces or tends to produce a change in its state of rest or of uniform motion.

→ One Newton Force: It is the force that produces an acceleration of 1 ms-2 in a body of mass 1 kg. It is denoted by ‘N’.

→ Balanced Forces: If a number of forces acting on an object do not produce any change in its state then these forces are called Balanced Forces. Their net result is zero force.

→ Unbalanced Forces: If the result of various forces acting on an object is not zero, then these forces are called unbalanced forces.

→ Frictional Force: It is the opposing force that comes into play when a body moves over the surface of another body.

→ Inertia: It is the property of the bodies due to which they cannot change their position of rest or of uniform motion unless some external force is applied.

→ The inertia of Rest: It is the property by virtue of which a body at rest will continue to remain at rest unless some external force is applied to bring about that change.

→ The inertia of Motion: It is the property of a body by virtue of which the body in motion, will continue to move with the same uniform speed unless some external force is applied to bring about that change.

→ Momentum: The product of mass and velocity possessed by a body is called its momentum.

→ Law of Conservation of Momentum: If no external force acts on a system of particles then the total momentum of the system remains conserved.

→ Newton’s Second Law of Motion: Tine rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction of the force.

→ Newton’s Third Law of Motion: Every action has an equal and opposite reaction.

→ Newton’s First Law of Motion: If a body is at rest, it will continue to remain at rest. And if a body is moving with a uniform velocity in a straight line it will continue to do so unless some external force is applied to bring about that change in its state.