Project Work: Types of Forces PDF

PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 1  PROJECT WORK Name of the Student :...

PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 1  PROJECT WORK Name of the Student : Class : VIII Subject : Physical Science Name of the Lesson : Force and Pressure Title of the Project : Types of forces Objectives of the project : From this project, students can able to understand the types of forces and examples for these forces. Introduction: A push or a pull on an object is called a force. An interaction of one object with another object results in a force between the two objects. A force can change the state of motion. A force may change the shape of the object, Type of Forces We can classify forces in two broad categories: 1. Contact forces 2. Non-Contact forces 1. Contact Forces We call those forces as contact forces which result when two interacting bodies are in direct physical contact with each other. Some of the examples of contact forces are 1. Muscular force 2. Frictional force. Muscular force: PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 2 In our daily life, we push, pull or lift many things. The effort (force) is caused by the action of muscles in our body. Animals, like bullocks, horses and camels, have been used for pulling carts. In arctic regions, reindeers are made to pull the sledges that are used as passenger vehicles. In these cases, the muscles of animals apply the force. This force is called muscular force. The force resulting due to the action of muscles is known as the muscular force. All animals, including human beings, use muscular force for most of their activities. Since muscular force can be applied only when it is in contact with an object, it is also called a contact force. Frictional force: A ball rolling along the ground gradually slows down and finally comes to rest. When we stop pedalling a bicycle, it gradually slows down and finally comes to a stop. A car or a scooter also comes to rest once its engine is switched off. Similarly, a boat comes to rest if we stop rowing it. In all these situations no force appears to be acting on the objects, yet their speed gradually decreases and they come to rest after some time. The force responsible for changing the state of motion of objects in all these examples is the force of friction. The force of friction always acts on all the moving objects and its direction is always opposite to the direction of motion. Since the force of friction arises due to contact between surfaces, it is also an example of a contact force. 2. Non-Contact Force: We call those forces as non-contact forces which can cause their effects even when the two interacting bodies are not in direct physical contact with each other. Here they are able to exert a push, or pull, despite their separation. Some examples of non-contact forces are: 1. Gravitational force 2. Magnetic force 3. Electric force. Gravitational force: PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 3 We know that when we throw a ball upwards, the ball goes up in the air but then falls down again. Ripe fruits that grow on trees, fall to the ground by themselves. This happens, due to a force, we call as the gravitational force. Objects or things fall towards the earth because it pulls them. This force is called the force of gravity. Gravitational force is a force acting on objects without contact them. So gravitational force is an example for non-contact force. Magnetic force: The magnetic property of lodestone was known to mankind since quite early times. Magnets have the well-known property of attracting objects made of iron. Likes poles of two magnets repel and unlike poles of two magnets attract each other. A magnet can exert a force on another magnet without being in contact with it. The force exerted by a magnet is an example of a non-contact force. Similarly, the force exerted by a magnet on a piece of iron is also a noncontact force. Electrostatic force: Two charged bodies exert a force on each other. When a glass rod is rubbed with a silk cloth, the rod becomes positively charged. Similarly, when an ebonite rod is rubbed with wool, the rod acquires a negative charge. Bring this charged ebonite rod near the suspended (and charged) glass rod. You will find that the suspended glass rod moves towards the charged ebonite rod. From these observations, we observe that like charges repel and unlike charges attract. This attraction, or repulsion, between charges is due to the electrostatic force between them. The force exerted by a PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 4 charged body on another charged or uncharged body is known as electrostatic force. This electrostatic force comes into play even when the bodies are not in contact. The electrostatic force, therefore, is another example of a non-contact force. References : VIII and X class Physical Science text books, internet Acknowledgements: I am very thankful to our Parents and Our Physical Science Teacher Sri E Y Das sir for helping in developing this project work. Also thanks to our friends who cooperated to me to do this project work by collecting the pictures and information from internet. PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 5 PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 6  PROJECT WORK Name of the student : Class : VIII Subject : Physical Science Topic : Sound Title of the Project : Noise pollution Introduction : We know that a sound is a form of energy. Sometimes the sound can be soothing to listen to and, at times, loud to hear. Sound can travel in the air and is produced by the vibration of objects. Regular exposure to a higher sound level that impacts humans and other living organisms is known as sound pollution. Objectives of the Project : This article will help us understand what noise pollution is, the types of noise pollution, and its causes and examples. And also helps us the remedies to prevent noise pollution. What is Noise Pollution? The word noise is derived from the Latin word ‘Nausea’, which means sickness in which one feels the need to vomit. Noise is the unpleasant and undesirable sound which leads to discomfort in human beings. The intensity of sound is measured in decibels (dB). The faintest sound that the human ear can hear is 1 Db. Due to increasing noise around the civilizations, noise pollution has become a matter of concern. Some of its major causes are vehicles, aircraft, industrial machines, loudspeakers, crackers, etc. When used at high volume, some other appliances also contribute to noise pollution, like television, transistor, radio, etc. PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 7 Types of Noise Pollution Following are the three types of pollution: Transport Noise It mainly consists of traffic noise which has increased in recent years with the increase in the number of vehicles. The increase in noise pollution leads to deafening of older people, headache, hypertension, etc. Neighbourhood Noise The noise from gadgets, household utensils etc. Some of the main sources are musical instruments, transistors, loudspeakers, etc. Weddings, public gatherings involve loudspeakers to play music resulting in the production of unwanted noise in the neighbourhood. Industrial Noise It is the high-intensity sound which is caused by heavy industrial machines. According to many researches, industrial noise pollution damages the hearing ability to around 20%. Constructional Noise: Mining, construction of buildings, etc add to the noise pollution. Recent days construction of buildings, bridges, roads etc., are continuously going on by the name of civilization and development. This created more noise. Transport noise Neighbourhood Noise Industrial noise Constructional noise PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 8 Noise Pollution Examples Following are the examples of noise pollution: Unnecessary usage of horns Using loudspeakers either for religious functions or for political purposes Unnecessary usage of fireworks Industrial noise Construction noise Noise from transportation such as railway and aircraft Effects of Noise Pollution on Human Health Noise pollution can be hazardous to human health in the following ways: Hypertension: It is a direct result of noise pollution which is caused due to elevated blood levels for a longer duration. Hearing loss: Constant exposure of human ears to loud noise that are beyond the range of sound that human ears can withstand damages the eardrums, resulting in loss of hearing. Sleeping disorders: Lack of sleep might result in fatigue and low energy level throughout the day affecting everyday activities. Noise pollution hampers the sleep cycles leading to irritation and an uncomfortable state of mind. Cardiovascular issues: Heart-related problems such as blood pressure level, stress and cardiovascular diseases might come up in a normal person and a person suffering from any of these diseases might feel a sudden shoot up in the level. Prevention of Noise Pollution Some noise pollution preventive measures are provided in the points below. Honking in public places like teaching institutes, hospitals, etc. should be banned. In commercial, hospital, and industrial buildings, adequate soundproof systems should be installed. Musical instruments’ sound should be controlled to desirable limits. Dense tree cover is useful in noise pollution prevention. Explosives should not be used in forest, mountains PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 9 PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 10  PROJECT WORK Name of the student : Class : VIII Subject : Physical Science Topic : LIGHT Title of the Project : Structure of human eye – Precautions for eye care Introduction: The human eye is one of the most important sense organs, It enables us to see the objects and colours around us. In this project, we learn about the parts of human eye and their function, how we have to take care about eyes. Objectives of the Project: This article will help us to understand (i) what are the various parts of human eye? (ii) How they are functioning in our human eye? (iii) How can we take care of our eyes? (iv) What are common defects in eye vision? Human eye: PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 11 The eye ball is nearly spherical in shape. The front portion is more sharply curved and is covered by a transparent protective membrane. This transparent spherical membrane over the bulge in the front of the eyeball is called Cornea. Between the cornea and the lens, there is a dark muscular structure or diaphragm called Iris. Iris has a small hole in it which is called a Pupil. Iris gives distinctive color to the eye. Iris also controls the amount of light entering into the eyes by controlling the size of the Pupil. If the light is dim then the pupil will open wide or dilate to allow more light to enter the eye and if the light is bright then the pupil will open less or contract so that less light enters into it. Behind the pupil of the eye, there is a lens that is thicker at the center i.e. it is a convex lens. It is the most sensitive part of the eye. The lens focuses the light on the back of the eye. The lens is held in its position by the ciliary muscles. The layer on the back of the human eye is called Retina. It works like a screen where the lens focuses the light and the image of the object is formed. The Retina contains several nerve fibers and blood vessels. There are two kinds of nerve cells:- 1) Cones: Cones are sensitive to bright light and also sense color. 2) Rods: Rods are sensitive to dim light. Sensations felt by the nerve cells are then transmitted to the brain through the optic nerve. The point at which the optic nerve leaves the eye has no sensory cells, so no vision is possible at that spot. This spot is called The Blind Spot PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 12 Near Point and Far point of the eye: The nearest point up to which the human eye can see clearly is called the near point. It is approximately 25 cm for a normal human eye. The farthest point up to which the eye can see is the far point. It is infinite for normal vision. The minimum distance up to which the human eye can see objects distinctly is called the least distance of distinct vision. It varies with age. Persistence of Vision:- The impression of an image does not vanish immediately from the Retina. It persists there for about 1/16th of a second. If still images of a moving object are flashed on the eye at a rate faster than 16 images per second, then the human eye perceives this object as moving. Eye defects in vision: 1. Myopia (near sightedness) : Some people can see objects near to them clearly but cannot see distant objects. They need a concave lens to see the distant objects clearly. 2. Hypermetropia (far-sightedness): Some people cannot see nearby objects clearly but can see distant objects. They need a convex lens to see nearby objects Normal vision Myopia Hypermetropia 3. Presbyopia: This happens due to gradual weakening of the ciliary muscles and diminishing flexibility of the eye lens. This effect can be seen in old age people. These people cannot see both nearby objects as well as far objects clearly. For these people doctors advises bi-focal lens. 4. Cataract: Sometimes, particularly in old age, eyesight becomes foggy. It is due to the eye lens becoming cloudy. When it happens, patients are said to have CATARACT. There is a loss of vision. It is possible to treat this disorder. The opaque lens is removed and a new artificial lens is inserted. PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 13  5. Astigmatism: An eye defect either in cornea or in lens caused by a deviation from spherical curvature, which results in distorted images, as light rays are prevented from meeting at a common focus. Astigmatism can be adjusted by using suitable lens. 6. Visually challenged people : People who have poor vision or cannot see are said to be visually challenged.Visually challenged people can read or write through a special system called BRAILLE SYSTEM. It was developed by Louis Braille in 1821. Caring for your eyes 1. Wear sunglasses whenever you go out in the sun to protect your eyes from the harmful ultraviolet radiation of the sun. Do not look sun directly. 2. Wash your eyes frequently with cold water. Never rub your eyes frequently. 3. Too little or too much light is very bad to eyes. Insufficient light causes eyestrain and headaches. Too much light, like the light from sun or laser, a powerful lamp or bulb can injure the retina. PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 14  4. Always read at normal distance for vision. Do not read by bringing the books too close or too far from your eyes. 5. If any defect in vision, go to doctor and use spectacles regularly. 6. Don’t focus too much of time with mobiles, tabs, desk tops etc. 7. Give at least 6 to 8 hours of rest to your eyes. Sleep well. Don’t read or see books or mobiles by sleeping on bed. 8. Take good diet which is enhance your eye sight with vitamin A such as carrots, fish, papaya like green leaves, fruits, vegetables and protein food. References : VIII and X class Physical Science text books, internet Acknowledgements: I am very thankful to our Parents and Our Physical Science Teacher Sri E Y Das sir for helping in developing this project work. Also thanks to our friends who cooperated me to do this project work by collecting the pictures and information from internet. PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 15 PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 16  Normal vision Myopia Hypermetropia PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 17  PROJECT WORK Name of the student : Class : VIII Subject : Physical Science Topic : Some natural phenomena Title of the project : Earth quakes Objectives of the project : To know about the earth quakes, causes, effects and precautions Introduction - Earthquake An earthquake is a sudden shaking (or trembling) of the earth which lasts for a very short time.An earthquake is caused by the violent movements of rocks deep inside the earth’s crust Earthquakes can cause immense damage to houses, other buildings, bridges, dams and people, etc. A lot of people get killed when they get buried under the debris of collapsed houses and other buildings during an earthquake. Earthquakes can also cause floods, landslides, and tsunamis A major earthquake occurred in India on 26th January 2001 in Bhuj district of Gujarat. Another major earthquake occurred on 8th October 2005 in Uri and Tangdhar towns of North Kashmir. A great loss of human life and property occurred in both these earthquakes. Earthquake is a destructive natural phenomenon which cannot be predicted in advance. Nobody can tell when and where an earthquake will occur. This unpredictable nature ofearthquakes makes them even more dangerous. In order to understand why earthquakes occur, we should first understand the inner structure of the earth. Inside Earth PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 18 The inside of earth is made up of three main layers : Core, Mantle and Crust. (1) Core The innermost part of the earth is called its core. The core of earth is made up mostly of iron. The core of earth is extremely hot. Most of the earth’s core (called outer core) is liquid (molten iron) whereas the inner part of core (called inner core) is under such high pressure that it is solid. (2) Mantle The central region of earth (between the core and crust) is called mantle. Mantle is the middle layer of the earth. Mantle is mostly made of dense, solid rocks. Some of the mantle is a mixture of solid rocks and hot molten rocks (liquid rocks) like the lava from a volcano. (3) Crust The outermost layer of earth is called crust. The crust of earth is made of comparatively lighter rocks than that of mantle. The crust of earth is thicker where there is land (or continents). The crust of earth under the oceans is thinner. The crust of earth is made of many huge pieces of flat rocks. Each piece of the earth’s crust is called a plate. The plates of earth on which continents exist are called continental plates whereas those plates of earth on which oceans exist are called oceanic plates. Occurrence of Earthquake The earthquakes occur when the moving plates of the earth’s crust : (1) slide past one another, and (2) collide with one another. PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 19  (1) The plates of earth’s crust are made up of huge rocks having rough edges. Due to their highly rough edges, the movement of two crust plates relative to one another is not smooth. When the two huge plates of earth’s crust slide past one another, they rub against one another ferociously and the rocks on their edges get entangled. Due to entanglement of the rocks at their edges, the two crust plates stop moving for some time. During this time, the plates are still pushing against one another and trying to move but they are not moving. This builds up pressure between the two plates of crust. When sufficient pressure has been built up between the two crust plates, the entangled rocks of the two crust plates break open suddenly with a big jolt. Then earthquake occurs releasing a tremendous amount of energy. This sudden release of tremendous amount of energy produces shock waves (or seismic waves) which make the earth shake. After the earthquake, the plates of earth’s crust start moving again and continue to move until they get entangled again. (2) When the two plates of the earth’s crust moving in opposite directions collide with each other head on, then the ends of these crust plates buckle and fold forming new mountains and causing earthquakes. A tremendous amount of energy is released when the two huge plates of the earth’s crust collide with each other. This tremendous amount of energy sends shock waves (called seismic waves) throughout the earth. When these shock waves reach the surface of earth, the ground starts shaking violently. This shaking of the ground is felt as an earthquake. Seismic zones or Fault zone The weak zones of earth’s crust (which are more prone to earthquakes) are called seismic zones’ or fault zones. Major earthquakes occur in the well defined ‘seismic zones’ called earthquake belts. The seismic zones mark the edges of the huge mobile pieces of the earth’s crust called plates.. In India, the areas most threatened by earthquakes are Kashmir, Western and Central Himalayas, the whole of North-East, Rann of Kutch, Rajasthan and Indo-Gangetic Plane. Some areas of South India also fall in earthquake danger zone. PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 20 Seismograph Earthquake tremors produce shock waves (called seismic waves). The shock waves travel in all directions through the Earth and also reach the surface of the earth. Seismograph is an instrument which measures and records the magnitude of an earthquake in terms of the shock waves it produces. Seismograph detects the shock waves produced by an earthquake and also records the shock waves on the paper in the form of a graph. Seismograph is also known as seismometer. A seismograph consists of a heavy weight suspended from a support with the help of a strong wire. The support is attached to the base of seismograph. And the base of seismograph is fixed rigidly to a solid rock on the surface of earth. A pen is attached to the lower end of the hanging heavy weight. This pen can trace lines on a graph paper wound around a rotating drum which lies beneath it. PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 21 Working of Seismograph When an earthquake occurs, the earth starts shaking due to which the base of seismograph fixed to the earth also starts shaking. But the freely suspended heavy weight (and the pen attached to it) do not shake during the earthquake, they remain stationary. Since the graph paper on the rotating drum shakes with the shaking earth, the pen attached to suspended weight records the vibrations produced by earthquake on the graph paper which moves under it. The pen traces the relative movement between the shaking earth and the stationary, suspended heavy weight. This trace on the graph paper records the earthquake. The seismograph record is also known as seismogram. Epicentre Focus is actually source of an earthquake. The point on earth’s surface directly above the focus is called epicentre. Richter Scale The magnitude (or intensity) of an earthquake is expressed on the Richter Scale. The Richter Scale is a series of numbers from 1 to 12 used to express the magnitude (or size) of an earthquake. An earthquake of magnitude 2 is ten times as strong as an earthquake of magnitude 1.An earthquake of magnitude 3 on Richter Scale is 100 times as strong as an earthquake of magnitude 1 on the same scale. And an earthquake of magnitude 6 on the Richter Scale is 1000 times stronger than an earthquake of magnitude 4. An earthquake of magnitude 6 on Richter Scale has 1000 times more destructive energy than an earthquake of magnitude 4. An earthquake of magnitude 1.5 on the Richter Scale is the smallest earthquake that can be felt by us. An earthquake of magnitude 4.5 on the Richter Scale causes some damage but not much damage. The earthquakes having magnitudes higher than 7 on the Richter Scale are really destructive earthquakes. Both, Bhuj and Kashmir earthquakes had magnitudes greater than 7.5 on the Richter Scale. The earthquakes which measure 8.5 or more on Richter Scale are devastating. During these earthquakes, the affected part of earth’s surface shakes violently. Such earthquakes can destroy entire cities and villages causing a great loss of life and property. Protection Against Earthquakes PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 22 Earthquakes are highly destructive and they cannot be predicted. So, it is necessary that we take precautions to protect ourselves all the time. Some of the important precautions which can be taken by the people living in seismic zones for protection against earthquakes are as follows: (i) All the houses and other buildings in seismic zones should be designed and constructed in such a way that they can withstand major earthquake tremors. (ii) In highly seismic areas, the use of mud and timber (wood) for building houses is better than using heavy construction materials. The roofs of houses in such areas should be kept as light as possible so that a roof falls during an earthquake, the damage will not be too much. (iii) The cupboards and shelves should be fixed to the walls so that they do not fall easily when shaking occurs during an earthquake. Glass bottles should not be placed on high shelves and heavy objects should be placed low to the ground. (iv) The objects such as heavy mirrors, photo frames, wall clocks and water-heaters, etc, should be mounted securely on the walls at such places in the house that they do not fall on the people in the house in the event of an earthquake. (v) All buildings (especially tall buildings) should have fire-fighting equipment in working order. In case an earthquake occurs, we should take the following precautions to protect ourselves depending on whether we are at home or outdoors at that moment. If we are at home when an earthquake occurs, then: (1) We should take shelter under a sturdy table or a kitchen counter and stay there till the shaking due to earthquake stops. We should cover our head with hands. (2) We should stay away from tall and heavy objects (like steel almirahs, cabinets, book racks and refrigerators), so that if they topple , they may not fall on us. (3) We should also stay away from glass windows that may shelter due to vibrations. (4) If we are in bed, we should just move on the bed to be close to a wall but not get up from the bed. We should protect our head with a pillow. If we are outdoors when an earthquake occurs, then: (1) We should stay at a clear spot away from buildings, trees and over-head power lines. We should also sit on the ground. (2) If we are in a car (or bus), we should not come out of it. The car (or bus) should be driven slowly to a clear spot away from buildings, trees and over-head electric wires. PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 23 PREPARED BY: E.Y.DAS, M.SC., B.ED., SA(PS), ZPHS, SHAREEN NAGAR, KALLUR (M), KURNOOL DIST. CELL: 9491412662 24