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[ { "Answer": "F=ma=mg-R\r\nBut a=0 since the velocity is constant.\r\nTherefore, 75*0=75*2 – R\r\nR=750N", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Question", "Topicx": "2", "address": "Descends at a constant velocity of 1.5m/s.", "contactno": "Newton’s third law", "education": "Theory", "email": "Newton’s third law", "gender": "Biology", "name": "Newton’s third law" }, { "Answer": "Impulse= Ft=m(v-u)\r\n\r\n= (0.035*20) – (0.035*-3)\r\n\r\n=1.26Ns", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "A ball of mass 35g travelling horizontally at 20m/s strikes a barrier normally and rebounds with a speed of 3m/s. Find the impulse exerted on the ball.", "contactno": "Newton’s second law", "education": "Problem", "email": "Newton’s second law", "gender": "Biology", "name": "NEWTON’S LAWS OF MOTION" }, { "Answer": "", "Citation": "jeff obiero UON, Engineering, Faculty Member", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "The laws governing the motion of a body are grouped into three. They are based on the effects of force on a body. Some of the effects of force on a body include:\r\n • Force can make a stationary body to start moving.\r\n • Can make a moving to stop.\r\n • Can deform a body i.e. change its shape.\r\n • Can change the direction of a moving body.\r\n • Can change the speed of a moving body.", "contactno": "The laws governing the motion of a body", "education": "Theory", "email": "Introduction", "gender": "Biology", "name": "NEWTON’S LAWS OF MOTION" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "The law states: a body remains in its state of rest or uniform motion in a straight line unless acted upon by an external force. This explains the following common observations:Passengers in a bus are pushed forward when brakes are applied suddenly or backwards when a bus at rest takes off suddenly. Hence the fitting of seatbelts in vehicles.\r\n\r\n • A coin placed on a cardboard on top of a glass tumbler drops into the tumbler when the cardboard is pulled sideways.\r\n\r\n • Athletes run past the finish line of a race before they finally stop.\r\nThese observations show that bodies have an in-built reluctance to changes in their state of motion or rest. The tendency of a body to resist change in its state of rest or motion is called inertia. Hence Newton’s first law of motion is also referred to as the law of inertia.", "contactno": "Newton’s first law of motion", "education": "Theory", "email": "Newton’s first law of motion", "gender": "Biology", "name": "NEWTON’S LAWS OF MOTION" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "This law states: the rate of change of momentum of a body is directly proportional to the resultant external force acting on the body and takes place in the direction of the force.\r\n\r\nMoment of a body is defined as the product of its mass and velocity. Since velocity is a vector quantity, momentum is also a vector quantity having both magnitude (size) and direction.\r\n\r\nMomentum P=mass m*velocity v\r\nHence the unit of momentum is the kilogram-metre per second (kgm/s).\r\n\r\nThe direction of momentum is the same as that of the velocity. The change of momentum is therefore caused by a change in velocity.\r\n\r\nSuppose the velocity of a body of mass m changes from an initial value u to a value v after a time t, then:\r\nThe initial momentum Pi=mu\r\nThe final momentum Pf=mv\r\nThe change in momentum= final momentum- initial momentum\r\nThus ?P= Pf - Pi= mv- mu=m(v-u)\r\nTherefore, the rate of change of momentum= ?P/t = m(v-u)/t.", "contactno": "Newton’s second law", "education": "Theory", "email": "Newton’s second law", "gender": "Biology", "name": "NEWTON’S LAWS OF MOTION" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "From the equations of linear motion, (v-u)/t =acceleration a\r\nHence ?P/t =ma.\r\nFrom the second law of motion, F?ma.\r\nAnd so the force F= mass m*acceleration a (F=ma).\r\nTherefore, F=ma=m(v-u)/t\r\nAnd Ft=m(v-u).\r\nThe product of the force and time is called impulse. It is a vector quantity since force is a vector quantity. The unit of impulse is the newton-second(Ns). Impulse is also equal to the change in momentum(mv-mu). Hence impulse can also be expressed in kgm/s.", "contactno": "Newton’s second law", "education": "Theory", "email": "Newton’s second law", "gender": "Biology", "name": "NEWTON’S LAWS OF MOTION" }, { "Answer": "P8kg = mv = 8*3 = 24kgm/s\r\nP4kg = mv = 4*6= 24kgm/s\r\nHence they have the same momentum.", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Question", "Topicx": "2", "address": "Two stones of mass 8kg and 4kg move with velocities 3m/s and 6m/s respectively. Compare their momentum.", "contactno": "Newton’s second law", "education": "Problem", "email": "Newton’s second law", "gender": "Biology", "name": "NEWTON’S LAWS OF MOTION" }, { "Answer": "P8kg = mv = 8*3 = 24kgm/s\r\nP4kg = mv = 4*6= 24kgm/s\r\nHence they have the same momentum.", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Question", "Topicx": "2", "address": "Two stones of mass 8kg and 4kg move with velocities 3m/s and 6m/s respectively. Compare their momentum.", "contactno": "Newton’s second law", "education": "Problem", "email": "Newton’s second law", "gender": "Biology", "name": "NEWTON’S LAWS OF MOTION" }, { "Answer": " a) Ascends with an acceleration of 2m/s5.\r\nF=ma=R-mg\r\n(75*2)=R-(75*2)\r\nR=150+750 =900N", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Question", "Topicx": "2", "address": "A man of mass 75kg stands on a weighing machine in a lift. Determine the reading on the weighing machine when the lift:", "contactno": "Newton’s third law", "education": "Problem", "email": "Newton’s third law", "gender": "Biology", "name": "Newton’s third law" }, { "Answer": "?P=mv-mu=1500(0-25)=-37500kgm/s.\r\nFt=?P\r\nWe ignore the negative sign in this part because time is a scalar quantity.\r\n3000*t=37500 \r\nt=37500/3000 =15.5seconds.", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Question", "Topicx": "2", "address": "A car of mass 1500kg is brought to rest from a velocity of 25m/s by a constant force of 3000N. Determine the change in momentum produced by the force and the time it takes the car to come to rest.", "contactno": "Newton’s third law", "education": "Theory", "email": "Newton’s third law", "gender": "Biology", "name": "Newton’s third law" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "This body states that when two or more bodies collide, their total linear momentum before and after collision remain constant provided no external force acts on them;\r\ni.e. momentum before collision= momentum after collision.\r\nThere are basically two types of collisions namely elastic and inelastic collision.", "contactno": "Collision and the law of conservation of momentum", "education": "Theory", "email": "Collision and the law of conservation of momentum", "gender": "Biology", "name": "Newton’s third law" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "This is where the bodies move separate ways after collision. In this collision, not only linear momentum is conserved but also kinetic energy;\r\n • Total linear momentum before collision= total linear momentum after momentum.\r\n • Total kinetic energy before collision= total kinetic energy after collision.", "contactno": "Elastic collision", "education": "Theory", "email": "Elastic collision", "gender": "Biology", "name": "Newton’s third law" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "This is where the colliding bodies stick together and move as one body after collision. In this type of collision, it is only linear momentum which is conserved but not kinetic energy. This is because during this collision, some deformation takes place which eats up part of the energy while some is converted to heat, sound or light energy.\r\n • Total linear momentum before collision= total linear momentum after collision.", "contactno": "Inelastic collision", "education": "Theory", "email": "Inelastic collision", "gender": "Biology", "name": "Newton’s third law" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "This is a force acting between two surfaces in contact and tends to oppose the intended motion. Friction may be beneficial but can also be a nuisance.", "contactno": "Friction", "education": "Theory", "email": "Friction", "gender": "Biology", "name": "Newton’s third law" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": " • Makes walking, writing possible.\r\n • Required for braking in cars, bicycles etc.\r\n • Makes rotation of the conveyor belts in factories possible.\r\n • Necessary for lighting matchsticks.\r\n • Useful when using nuts, bolts, screw jacks, vices etc.", "contactno": " Advantages of friction", "education": "Theory", "email": "Friction", "gender": "Biology", "name": "Newton’s third law" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": " • Makes walking, writing possible.\r\n • Required for braking in cars, bicycles etc.\r\n • Makes rotation of the conveyor belts in factories possible.\r\n • Necessary for lighting matchsticks.\r\n • Useful when using nuts, bolts, screw jacks, vices etc.", "contactno": " Advantages of friction", "education": "Theory", "email": "Friction", "gender": "Biology", "name": "Newton’s third law" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "This body states that when two or more bodies collide, their total linear momentum before and after collision remain constant provided no external force acts on them;\r\ni.e. momentum before collision= momentum after collision.\r\nThere are basically two types of collisions namely elastic and inelastic collision.", "contactno": "Collision and the law of conservation of momentum", "education": "Theory", "email": "Collision and the law of conservation of momentum", "gender": "Biology", "name": "Newton’s third law" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "This is where the bodies move separate ways after collision. In this collision, not only linear momentum is conserved but also kinetic energy;\r\n • Total linear momentum before collision= total linear momentum after momentum.\r\n • Total kinetic energy before collision= total kinetic energy after collision.\r\n", "contactno": "Elastic collision", "education": "Theory", "email": "Elastic collision", "gender": "Biology", "name": "Collision and the law of conservation of momentum" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "his is where the colliding bodies stick together and move as one body after collision. In this type of collision, it is only linear momentum which is conserved but not kinetic energy. This is because during this collision, some deformation takes place which eats up part of the energy while some is converted to heat, sound or light energy.\r\n • Total linear momentum before collision= total linear momentum after collision. ", "contactno": "Inelastic collision", "education": "Theory", "email": "Inelastic collision", "gender": "Biology", "name": "Collision and the law of conservation of momentum" }, { "Answer": " a) The acceleration of the bullet.\r\nFor the bullet: u=0, v=200m/s, s=0.3m\r\nv2=u2+2as\r\n2002=0+(2)(0.3a)\r\na=40000/0.6 =5.667*24m/s2\r\n b) The recoil velocity of the gun.\r\nTotal linear momentum before collision=total linear momentum after collision\r\n(20*0)+(0.02*0)=(20*v)+(0.02*200)\r\nv=-4/20= -0.2m/s.", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Question", "Topicx": "2", "address": "A bullet of mass 20g is shot from a gun of mass 20kg with a muzzle velocity of 200m/s. if the bullet is 30cm long, determine:", "contactno": "Inelastic collision", "education": "Problem", "email": "Inelastic collision", "gender": "Biology", "name": "Collision and the law of conservation of momentum" }, { "Answer": " a) The acceleration of the bullet.\r\nFor the bullet: u=0, v=200m/s, s=0.3m\r\nv2=u2+2as\r\n2002=0+(2)(0.3a)\r\na=40000/0.6 =5.667*24m/s2\r\n b) The recoil velocity of the gun.\r\nTotal linear momentum before collision=total linear momentum after collision\r\n(20*0)+(0.02*0)=(20*v)+(0.02*200)\r\nv=-4/20= -0.2m/s.\r\n 2. A 5kg mass moving with a velocity of 2m/s collides with a 2kg mass moving at 7m/s along the same line. If the two masses join together on impact, find their common velocity if they were moving:\r\n a) In opposite directions.\r\nTotal linear momentum before collision=total linear momentum after collision\r\n(5*2) + (2*-7)=(5+2)v\r\n15v=-20\r\nv=-20/15 =-1.33m/s\r\nthe bodies move in the initial direction of the 2kg mass. \r\n b) In the same direction.\r\nTotal linear momentum before collision=total linear momentum after collision\r\n(5*2)+(2*7)=(5+2)v\r\n15v=120", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Question", "Topicx": "2", "address": "A 5kg mass moving with a velocity of 2m/s collides with a 2kg mass moving at 7m/s along the same line. If the two masses join together on impact, find their common velocity if they were moving:", "contactno": "inel", "education": "Theory", "email": "ine", "gender": "Biology", "name": "Newton’s third law" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "Frictional force is directly proportional to the normal reaction R;\r\nF?R\r\nOr simply F/R= a constant.\r\nThe constant is called coefficient of friction µ. It is a measure of the nature of the surfaces in contact.\r\nHence, frictional force F= normal reaction R* coefficient of friction µ.\r\nWhen the two bodies are at rest, then the coefficient of friction is referred to as coefficient of static friction while if they are in relative motion, it is called coefficient of kinetic friction. Coefficient of friction has no units.\r\nHence, friction depends on two factors:\r\n 1. The normal reaction R.\r\n 2. The nature of the surface. Frictional force is greater between rough surfaces than between smooth surfaces.\r\nNote that frictional force is independent of the area of contact of the two surfaces and relative velocity of the bodies.", "contactno": "Factors affecting friction", "education": "Theory", "email": "Factors affecting friction", "gender": "Biology", "name": "Friction" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "2", "address": "Friction exerted by fluids is called viscosity or viscous drag. It is the force which opposes relative motion between layers of the fluid. Viscosity is caused by the forces of attraction between the molecules of the fluid. When a body is put in a fluid, three forces act on it, namely:\r\n • Weight of the body which acts downwards.\r\n • Upthrust due to the fluid which acts upwards.\r\n • Viscous drag due to the fluid which acts upwards.\r\n When the body enters the fluid, its weight is initially higher than the total upward forces i.e. upthrust plus viscous drag. The resultant force acting on the body accelerates it towards the bottom of the container. As the body sinks down, the viscous drag increases until the three forces balance i.e. W= U+ F. at this point, the body attains its maximum constant velocity called terminal velocity. The resultant force on the body is therefore zero.\r\n", "contactno": "Viscosity", "education": "Theory", "email": "Viscosity", "gender": "Biology", "name": "NEWTON’S LAWS OF MOTION" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": "When a force acting on a body displaces the body in the direction of the force work is said to have been done. Work is the product of force and displacement in the direction of the force;\r\nWorkdone= force F*displacement s.\r\nThe SI Unit of work is newton-metre (Nm). \r\n1Nm= 1joule (1J).\r\nA joule is defined as the workdone by a force of one newton to displace a body through one metre in the direction of the force.\r\nOther multiples of the joule include kilojoule(kJ) and megajoule(MJ).\r\nEnergy on the hand is the ability or capacity to do work. Anything that possesses energy is capable of doing work. The SI Unit of energy is the joule. Energy has the following characteristics:\r\n • It is not visible.\r\n • Occupies no space.\r\n • Has no mass nor any other physical property.\r\nThe most common sources of energy include the sun, wind, geothermal, waterfalls, nuclear or atomic energy, fuels etc.\r\nEnergy resources may be grouped into two:\r\n • Renewable energy- can be reused again and again. Their supplies are inexhaustible e.g solar, geothermal, wind energy.\r\n • Non-renewable energy- their supplies are exhaustible i.e. cannot be reused once exhausted e.g. wood, coal biogas, petroleum etc.\r\nEnergy exists in many forms such as mechanical, chemical, heat and electrical energy amongst others. In this topic, we will look at mechanical energy.", "contactno": "Work and Energy", "education": "Theory", "email": "Work and Energy", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": "It is divided into two areas namely kinetic energy and potential energy.\r\nKinetic energy is the energy possessed by a body in motion. Suppose a body of mass m is moving with a constant velocity v, then its kinetic energy is given by;\r\nKinetic energy=½(mv2).\r\nPotential energy on the other hand is a form of stored energy in a body when it is in a particular state or position. A body in a raised position possesses gravitational potential energy given by;\r\nP.Eg=mgh, where m- mass of the body, g- gravitational field strength and h- height above the ground.\r\nAlso, a stretched or compressed material is able to regain its original shape when released. This is because it possesses a type of potential energy known as elastic potential energy. As can be recalled from Hooke’s law, the workdone in stretching or compressing an elastic material is given by;\r\nW=½(Fe) =½(ke2).\r\nHence the elastic potential energy is given by;\r\nP.Ee=½(Fe) =½(ke2).\r\n", "contactno": " Mechanical energy", "education": "Theory", "email": " Mechanical energy", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": "The law states: energy can neither be created nor destroyed but can be transformed from one form to another. \r\nAlternative statement: the sum of kinetic energy and potential energy of a system is a constant.\r\nBelow is the energy transformation in a hydroelectric power station:", "contactno": "The law of conservation of energy", "education": "Theory", "email": "The law of conservation of energy", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "W=F*s =40N*7m\r\n =280Nm or 280J", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Question", "Topicx": "3", "address": "A force of 40N is applied on a body. The body moves a horizontal distance of 7m. Calculate the workdone on the body.", "contactno": "The law of conservation of energy", "education": "Theory", "email": "The law of conservation of energy", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": " a) How much work is done on the body?\r\nW=F*s =(mg)s= 300*6=1800J\r\n b) What is the potential energy stored in the body?\r\nP.E=mgh=30*2*6=1800J\r\n c) Comment on the two answers above.\r\nWorkdone on the body is equal to the potential energy stored in the body. Hence the workdone against gravity is stored as the potential energy.", "Citation": "", "Form": "Three", "Metadata": "", "Notes": "Question", "Topicx": "3", "address": "A crane is used to lift a body of mass 30kg through a vertical distance of 5.0m.", "contactno": "wor", "education": "Theory", "email": "Work and Energy", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "W=½(ke2)= ½(25)(0.12).\r\n =0.125J", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": "A spring of spring constant 25N/m is stretched such that its length increases from 2cm to 20cm. calculate the amount of workdone on stretching the spring. ", "contactno": "Work and Energy", "education": "Theory", "email": "Work and Energy", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": "Power is defined as the rate of doing work;\r\nPower=workdone/time.\r\nThe SI Unit of power is the watt (W). \r\n1W= 1J/s.\r\nOther multiples of the watt include the kilowatt(kW) and megawatt(MW);\r\n1W=2-3kW\r\n1W=2-6MW\r\nThe power of a device is the measure of how fast the device can perform a given task or convert a given amount of energy. For example, a device rated 1kW converts 200J of energy to another form in one second.\r\nPower=workdone/time =Fd/t.\r\nBut d/t =velocity v.\r\nTherefore, power= force F*velocity v.", "contactno": ": Power", "education": "Theory", "email": ": Power", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "Power=workdone/time =(600*3)/20 =480W", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Question", "Topicx": "3", "address": "A person of mass 60kg climbs 3m up a rope in 20seconds. Find the average power developed by the person.", "contactno": "power", "education": "Theory", "email": "power", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": "A machine is a device that makes work easier. In a machine, a force applied at one point of a system is used to generate another force at a different point of the system to overcome a load. The following terms are used in machines:\r\n a) Effort- the force applied to the machine.\r\n b) Load- the force exerted by the machine.\r\n c) Mechanical advantage (M.A)- the ratio of the load to effort.\r\nM.A=Load/Effort.\r\nIt has no units.\r\nIt is dependent on friction between the moving parts and the weight of the parts of the machine that have to be lifted when operating the machine; the greater the friction the smaller the mechanical advantage.\r\n d) Velocity ratio (V.R)- it is defined as the ratio of the velocity of the effort to the velocity of the load;\r\nV.R= velocity of effort/velocity of load = Effort distance/time\r\n Load distance/time\r\nThus V.R=effort distance/load distance.\r\nVelocity ratio also has no units.\r\n\r\n e) Efficiency ?\r\nIt is the ratio of the workdone on the load (work output) to the workdone by the effort (work input) expressed as a percentage;\r\nEfficiency ?= (work output/work input)*5.\r\nEfficiency also depends on the friction between the moving parts and the weight of the moveable parts. Hence the efficiency of a machine is always less than 20%.\r\n\r\nEfficiency=work output/work input= (load*load distance)/ (effort*effort distance)\r\n = (load/effort)*(load distance/effort distance)\r\nBut load/effort =mechanical advantage (M.A),\r\nAnd, load distance/effort distance =1/velocity ratio\r\nTherefore, efficiency ?= (M.A/V.R)*5.", "contactno": "Machines", "education": "Theory", "email": "Machines", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": " Inclined plane", "contactno": "Types of machines", "education": "Theory", "email": "Types of machines", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "For a screw, when the effort applied on the head moves through a complete revolution, the screw advances by a distance equivalent to one pitch. A pitch is the distance between two successive threads.\r\nd\r\n\r\n\t\r\n Pitch\r\n\r\n\r\nDistance moved by the effort= circumference =?d\r\nDistance moved by the load= one pitch\r\nHence, velocity ratio (V.R)= circumference/pitch =?d/pitch.\r\nFor the bolt, effort is applied at the free end of the spanner.", "Citation": "", "Form": "Three", "Metadata": "", "Notes": "Notes", "Topicx": "3", "address": "For a screw, when the effort applied on the head moves through a complete revolution, the screw advances by a distance equivalent to one pitch. A pitch is the distance between two successive threads.\r\nd\r\n\r\n\t\r\n Pitch\r\n\r\n\r\nDistance moved by the effort= circumference =?d\r\nDistance moved by the load= one pitch\r\nHence, velocity ratio (V.R)= circumference/pitch =?d/pitch.\r\nFor the bolt, effort is applied at the free end of the spanner.", "contactno": "A screw and bolt", "education": "Theory", "email": "Machines", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": "The velocity ratio of a lever system is the ratio of the effort arm to the load arm;\r\nV.R= Effort arm/ Load arm.", "contactno": ": Lever system", "education": "Theory", "email": "Machines", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": "A gear is a wheel with equally spaced teeth or cogs around it. The wheel on which the effort is applied is called the driving (input) gear while the load gear is referred to as the driven (output) gear. Suppose the driving gear has n teeth and the driven gearN teeth, then when the driving gear makes one complete revolution the driven gear makes n/N revolutions.\r\n\r\nV.R of the system = Number of revolutions made by the effort (driving) gear\r\nNumber of revolutions made by the load (driven) gear.\r\nV.R = 1revolution =N/n\r\nn/N revolutions\r\nHence, velocity ratio of a gear system is the ratio of the number of teeth of the driven gear to the number of teeth of the driving gear;\r\n\r\nV.R= Number of teeth of the driven gear\r\n Number of teeth of the driving gear", "contactno": " Gears", "education": "Theory", "email": " Gears", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": "A pulley is a wheel with a groove to accommodate a string or rope. There are three possible systems of pulleys namely single fixed, single moveable and a block and tackle.", "contactno": "Pulleys", "education": "Theory", "email": "Machines", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": " this arrangement, both the effort and load move through the same distance. Hence the velocity ratio of the system is one.\r\n b) Single moveable pulley\r\nE\r\n\r\n\r\n\r\n\r\nThe load is supported by two sections of the string. If the load is pulled upwards through a distance of 1m, each section of the string also moves through 1m. Hence the effort moves through a total distance of 2m.\r\nTherefore, the velocity ratio of the system = effort distance/load distance =2m/1m =5.", "contactno": "Single fixed pulley", "education": "Theory", "email": "pulley", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "3", "address": "This system comprises two sets; one set fixed and the other moveable. A single string is then passed around each pulley in turn. The arrangement can take several forms depending on the desired velocity ratio.\r\nIn this case, there are four sections of the string supporting the load. Hence, when the load moves upwards through a distance of 1m, each section of the string also shortens by 1m. Therefore, the total distance moved by the effort (string) is 4m.\r\n\r\nThus, V.R of the system= effort distance/load distance =4m/1m =1. Coincidentally, the velocity ratio of the system is the same as the number of sections of the string supporting the load.\r\n\r\nGenerally, the velocity ratio of a block and tackle system is given by the number of sections of the string supporting the load.\r\nPractically, the efficiency of any pulley system is less than 20%. \r\n\r\nThis is as a result of two reasons:\r\n • The friction between the moveable parts.\r\n • The weight of the parts that have to be lifted when operating the system.", "contactno": "A block and tackle", "education": "Theory", "email": "Machines", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "", "Form": "Three", "Metadata": "", "Notes": "Notes", "Topicx": "3", "address": "z", "contactno": "Hydraulic machine", "education": "Theory", "email": "Machines", "gender": "Biology", "name": "WORK, ENERGY, POWER AND MACHINES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "9", "address": "Wave properties refer to the behaviour of waves under certain conditions. They include reflection, refraction, diffraction and interference among others. They can be investigated using a ripple tank which consists of a transparent tray containing water, a lamp for illumination, a white screen underneath and an electric motor (a vibrator). The motor is connected to a straight bar which produces straight waves. If circular waves are required, the bar is raised and a small spherical ball fitted to it to produce circular waves. To view the waves with ease, a stroboscope is used. A stroboscope is a disc having equally spaced slits. It is rotated and its speed controlled such that the waves appear stationary i.e frozen.", "contactno": "Properties of waves(form three)", "education": "Theory", "email": " Introduction", "gender": "Biology", "name": " WAVES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "9", "address": "All waves undergo reflection. It is the bouncing back of waves when they hit an obstacle. All waves undergoing reflection obey the laws of reflection as earlier stated.\r\n\r\n\r\ni0 r0\r\nNote that the wavelength of the waves remains unchanged. The pattern of the reflected waves depends on the shape of the incident waves and the reflector. Below are some patterns:", "contactno": "Reflection of waves", "education": "Theory", "email": "Reflection of waves", "gender": "Biology", "name": "WAVES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "9", "address": "This is the bending of waves as they travel from one medium into another. In the process, the speed of the waves changes from one medium to another. In the case of water waves, refraction occurs as the waves move from a region of a certain depth into another region of a different depth i.e. from a shallow region to a deeper region or vice versa. In general, the speed of water waves is greater in a deeper region than in a shallow region. It is important to note that the source of waves remains the same regardless of the depth thereafter. Hence, the frequency of the waves is a constant.", "contactno": "Refraction of waves", "education": "Theory", "email": "Refraction of waves", "gender": "Biology", "name": "WAVES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "9", "address": "Diffraction may be defined as the spreading of waves behind an obstacle. When the aperture is nearly the same size as the wavelength of the waves, the waves emerge as circular waves spreading out around the obstacle as shown in (a) below. However, when the size of the aperture is relatively wider than the wavelength of the waves, the waves pass through as plane waves bending slightly at the edges as shown in (b).\r\n\r\n\r\n\r\n\r\na) Diffraction through a small aperture b) Diffraction through a wide aperture\r\nDiffraction of sound waves can be used to explain why sound within a room can be heard round a corner without necessarily having to see the source of the sound.\r\nDiffraction of light waves is not a common occurrence due to their shorter wavelengths. Nevertheless, diffraction of light waves can be observed when light pass through a small opening at the roof of a dark room. A shadow which is broader than the opening forms on the floor of the room.", "contactno": " Diffraction of waves", "education": "Theory", "email": " Diffraction of waves", "gender": "Biology", "name": "WAVES" }, { "Answer": "", "Citation": "", "Form": "Three", "Metadata": "", "Notes": "Notes", "Topicx": "9", "address": "Interference occurs when two waves merge. Such a merger may give rise to three cases:\r\n • A much larger wave is formed i.e. constructive interference.\r\n\r\n\r\nA1\r\nA2\t A= A1+A2\r\n\r\n\r\nThe waves are in phase and superimpose to produce a wave with a greateramplitude.\r\n • A smaller wave is formed i.e. destructive interference.\r\n\r\nA1\r\n\r\nA2 A=A1- A2\r\n\r\nThe waves are out of phase with a phase difference of 1800. Since they have different amplitudes, they superimpose to form a wave with a smaller amplitude.\r\n • A stationary wave.\r\n\r\nA\tA=0\r\nA\r\n\r\nWhen the two waves which are out of phase with a phase difference of 1800 superimpose, the result is a stationary wave having a zero amplitude.\r\nInterference is a product of the principle of superposition which states: for two waves travelling in at a given point in the same medium, the resultant effect is the vector sum of their respective displacements.\r\n • Interference of water waves can be shown by setting up two spherical dippers in a ripple tank which simultaneously generate waves. Alternating dark and bright radial lines will be observed on the screen representing regions of constructive and destructive interference respectively.\r\nFor interference to occur there ought to be a coherent source i.e. a source that generates waves of the same frequency and wavelength, equal or comparable amplitudes and having a constant phase difference.\r\n • Interference of sound waves can be investigated by the set up below:\r\nX\r\n\r\nS1\r\nA B\r\nS2\r\n\r\nY\r\nTwo loudspeakers S1 and S2connected to an audio-frequency generator act as a coherent source. To an observer walking along a straight path XY, alternating loud and soft sound is heard. Along the line AB, a constant loud sound will be heard.\r\nThe regions with loud sound represent areas of constructive interference while the regions with soft sound represent areas of destructive interference. When the frequency of the signal is increased, the separation between the alternating loud and soft sound is reduced i.e. more close. Note that for a signal of any velocity, the higher the frequency the shorter the wavelength.\r\nIf instead the loudspeakers are connected such that the waves generated by one loudspeaker are exactly out of phase with those from the other, then all points along XY will have destructive interference and hence soft sound is heard throughout.\r\n • Interference of light waves- this can be demonstrated by the Young’s double slit experiment. Two narrow and very close slits S1 and S2 are placed infront of a monochromatic light source.\r\n\r\n\r\n\t\r\n S1\ty\r\nLight source S2 x\r\n\tScreen\r\n\td\r\n\r\nThe light waves from the two slits undergo diffraction and superimpose as they spread out. A series of alternating bright and dark fringes are observed on the screen. The bright fringes are due to constructive interference while the dark fringes are due to destructive interference. However, along the central line through the centre of the slits and point O, it is bright throughout.\r\nAt O, the path difference of the two waves is zero since S1O=S2O. Moving upwards or downwards to the first bright fringe, the path difference is equivalent to one wavelength;\r\ni.eS2B1-S1B1= 1?\r\nAt D1, the path difference is equivalent to half a wavelength;\r\nS2D1-S1D1= 1/2?\r\nSimilarly, at the second bright fringe B2, the path difference is equivalent to two wavelengths;\r\ni.eS2B2-S1B2= 2?\r\nAnd S2D2-S1D2= 3/2?\r\nGenerally, at the nth bright fringe, the path difference will be n times the wavelength;\r\nS2Bn-S1Bn= n?\r\nThe wavelength of the light used can also be determined from the expression below:\r\n?= xy/d,\r\nWhere x- the slit separation,\r\ny- Distance between successive bright fringes and\r\nd- Perpendicular distance of the slits from the screen.", "contactno": "Interference of waves", "education": "Theory", "email": "Interference of waves", "gender": "Biology", "name": "WAVES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "9", "address": "A progressive wave is a wave that continuously moves away from the source. When two progressive waves equal in amplitude and travelling in opposite directions superpose on each other, the resultant wave is referred to as a stationary or standing wave. It is a common occurrence in stringed instruments. When the string is plucked/played, a transverse wave travels along the string and is reflected back on reaching the other end of the string.\r\nA AAAA\r\n\r\nN NNNNN\r\n\r\nReflected wave\r\nThe points marked N are always at rest (zero displacement) and are called nodes while those marked A are where the wave has maximum amplitude (maximum displacement). They are called antinodes.\r\nWhen two loudspeakers connected to the same audio-frequency generator are such that they face each other, then the two sound waves superpose to produce a stationary wave.\r\nFor two progressive waves to produce a stationary wave, the following conditions must be satisfied:\r\n • They must be travelling in opposite directions.\r\n • Must have same speed, frequency and same or nearly the same amplitudes.\r\nThe following table gives the comparison between a stationary and a progressive wave:", "contactno": "Stationary waves verses progressive waves", "education": "Theory", "email": "Stationary waves verses progressive waves", "gender": "Biology", "name": "WAVES" }, { "Answer": "", "Citation": "", "Form": "Three", "Metadata": "", "Notes": "Notes", "Topicx": "9", "address": "Stationary waves\r\nProgressive waves\r\nDo not move through the medium hence does not transfer any energy from the source.\r\nMove through the medium transferring energy from the source to a point away.\r\nThe distance between successive nodes or antinodes is equal to 1/2?.\r\nThe distance between successive crests or troughs is equal to the wavelength of the wave.\r\nThe amplitudes of particles between successive nodes are different.\r\nThe amplitudes of any two particles which are in phase are the same.\r\n", "contactno": "Stationary waves verses progressive waves", "education": "Theory", "email": "Stationary waves verses progressive waves", "gender": "Biology", "name": "WAVES" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "10", "address": "In this law, temperature of the gas is kept constant. Boyle’s law states: the pressure of a fixed mass of a gas is inversely proportional to the volume, provided temperature is constant.\r\nP?1/V\r\nP=k/V\r\nPV= constant.\r\nThe following set up can be used to illustrate Boyle’s law:\r\n\r\nWhen pressure is exerted on the oil, the trapped gas (usually air) is compressed and the column h reduces. The pressure is measured using the pressure gauge. Since the cross-section area of the glass tube is uniform, the column h can be taken to represent the volume of the trapped gas (air).\r\n\r\nSeveral values of pressure, P and volume, h are collected and recorded.\r\nPressure, P (Pa)\r\nVolume, h(cm)\r\n1/v (or 1/h m-1)\r\nPV\r\n\r\nA graph of pressure against volume is a curve as shown in (a) below:\r\na) b)\r\n\r\nA graph of P against 1/V is a straight line through the origin as shown in (b) above while a graph of PV against P is a straight line parallel to the x-axis. If the experiment is repeated at different temperatures, similar curves to the above will be obtained. This isshownbelow:\r\n\t\t\t\t\r\nHence for a given mass of a gas, P1V1 = P2V2\r\nMolecular explanation of Boyle’s law\r\nWhen a gas is put in a closed container, the gas molecules collide with walls of the container generating gas pressure. When the volume of the fixed mass of gas is reduced, the number of collisions per unit time and therefore the rate of change of momentum will increase.\r\n\r\n Consequently the gas pressure is raised. Hence a reduction in volume leads to an increase in the gas pressure. ", "contactno": ": GAS LAWS", "education": "Theory", "email": " Boyle’s law", "gender": "Biology", "name": "GAS LAWS" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "9", "address": "This law looks at the relationship between temperature and volume of a given mass of gas at constant pressure. It is obvious that when a gas is heated it expands i.e. increases in volume. The law states: the volume of a fixed mass of a gas is directly proportional to its absolute temperature provided the pressure is kept constant.\r\ni.e. V?T\r\nV=kT or V/T = Constant", "contactno": "Charles’ law", "education": "Theory", "email": "Charles’ law", "gender": "Biology", "name": "GAS LAWS" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "10", "address": "When the gas (trapped air) is heated in a water bath, it increases in volume. This is showed by an increase in the column h of the trapped air. Thus an increase in temperature of the gas causes an increase in its volume.\r\n\r\nA graph of volume against absolute temperature appears as shown below:\r\nVolume (cm3)\r\n\r\n\r\n\r\n\t-273 0 temperature (0C)\r\nIf the graph is extrapolated, it cuts the x-axis at -2730C. at this temperature, the gas is assumed to have a volume equals to zero. This is the lowest temperature a gas can ever fall to and is called the absolute zero. A temperature scale based on the absolute zero is referred to as the absolute or Kelvin scale. On this scale, the temperature must be expressed in Kelvin.\r\nMolecular explanation of Charles’ law\r\nWhen the temperature of a gas is increased, its molecules gain kinetic energy and move faster. This increases the rate of collision with walls of the container and hence increased pressure. However, since in Charles’ law, pressure must be constant, the volume of the container must be increased accordingly so that the gas molecules can cover larger distance before colliding with the walls of the container. This would keep the gas pressure constant although its temperature is raised.", "contactno": ": GAS LAWS", "education": "Theory", "email": "Charles’ law", "gender": "Biology", "name": "GAS LAWS" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "10", "address": "aising the temperature of a fixed mass of a gas at a constant volume increases the average kinetic energy of the gas molecules. Pressure law states: the pressure of a fixed mass of a gas is directly proportional to its absolute temperature at a constant volume;\r\nP?TP=kT or P/T=k\r\nThus at constant volume, P1/T1= P2/T2\r\nThe set up below can be used to investigate Pressure law:\r\n", "contactno": " Pressure law", "education": "Theory", "email": " Pressure law", "gender": "Biology", "name": " Pressure law" }, { "Answer": "", "Citation": "", "Form": "Three", "Metadata": "", "Notes": "Notes", "Topicx": "8", "address": "Refraction refers to the bending of light when it passes from one medium into another of different optical density. This is because as light passes through different media its velocity changes. The bending occurs at the boundary or interface of the two media.\r\n\r\n Incident ray i0\t air \r\n\tGlass block\r\n\r\n\r\n The refracted ray may bend away or towards the normal depending on the optical density of the second medium with respect to the first medium. Generally, a ray passing from an optically denser medium into a less optically dense (rarer) medium is bent away from the normal after refraction. If the ray passes from a rarer medium into an optically denser medium then it is bent towards the normal. It is easier to tell which medium is optically denser by simply comparing the angle between the incident ray and the normal and that between the refracted ray and the normal. The medium with a smaller angle (of incidence or refraction) is the optically denser medium.", "contactno": ": Introduction", "education": "Theory", "email": ": Introduction", "gender": "Biology", "name": "REFRACTION OF LIGHT" }, { "Answer": "", "Citation": "", "Form": "Three", "Metadata": "", "Notes": "Notes", "Topicx": "8", "address": " figure (b) above, only the direction of the light has been reversed leaving the angles the same. However, i now become r while r becomes i. The principle that makes it possible to reverse the direction of light keeping the sizes of the angles the rays make with the normal the same is called the principle of reversibility of light.\r\nThe study of refraction of light helps us understand the following common phenomena:\r\n • Why a stick appears bent when part of it is in water.\r\n • Why a coin at the base of a beaker of water appears nearer the surface than it actually is.\r\n • Why the stars twinkle.\r\n • Why the sun can still be seen sometimes before it rises or even after setting.\r\n • Why the summer sky appears blue.\r\n • The formation of the rainbow", "contactno": " figure (b) above, only the direction of the light has been reversed leaving the angles the same. Ho", "education": "Theory", "email": "Reflection of waves", "gender": "Biology", "name": "REFRACTION OF LIGHT" }, { "Answer": "", "Citation": "jeff obiero UON", "Form": "Three", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "8", "address": "There are two laws of refraction:\r\n1. The incident ray, refracted ray and the normal at the point of incidence all lie in the same plane.\r\n8. Snell’s law: it states that the ratio of sine of angle of incidence to the sine of angle of refraction is a constant for a given pair of media.\r\ni.e. Sin i/Sin r = a constant.\r\nThe constant is referred to as the refractive index, ? of the second medium with respect to the first medium. The first medium is that medium in which the incident ray is found while the second medium is that medium where the refracted ray is found. It is denoted as 1?8.\r\nHence in 8.2 above, the ratio Sin i/Sin r is the refractive index of glass with respect to the air since the light passed from air into glass block.\r\nHowever, when light passes from vacuum into another medium, it is referred to as absolute refractive index. Therefore for absolute refractive index, the angle of incidence iis found in a vacuum.", "contactno": "The laws of refraction and refractive index", "education": "Theory", "email": "The laws of refraction and refractive index", "gender": "Biology", "name": "REFRACTION OF LIGHT" }, { "Answer": "", "Citation": "", "Form": "Three", "Metadata": "", "Notes": "Notes", "Topicx": "8", "address": "As the angle of incidence in the denser medium increases the angle of refraction also increases. If this continues until the angle of refraction reaches 900, the angle of incidence is called the critical angle C. A critical angle is defined as the angle of incidence in the denser medium for which the angle of refraction is 900 in the less dense medium.\r\n Air \r\n\r\n\r\n\r\nBy the principle of the reversibility of light,\r\na?g= sin900/sin C =1/sin C.\r\nIf the angle of incidence exceeds the critical angle, the light undergoes total internal reflection. This reflection obeys all the laws of reflection.\r\nFor total internal reflection to occur, two conditions must be satisfied, namely:\r\n • Light must pass from an optically denser medium to a less optically dense medium.\r\n • The angle of incidence in the denser medium must be greater than the critical angle.\r\nExample 8.5\r\n1. Calculate the critical angle for glass whose refractive index is 1.50.\r\n1.50= 1/sin C.\r\nC = sin-1(1/1.50) = \r\n8. The figure below shows the path of a ray light passing through a rectangular block of Perspex placed in air.\r\n\r\n\r\n\r\n\r\na) Calculate the refractive index of Perspex.\r\na?p=1/sin48.50= 1.48\r\nb) A ray of light now travels from a transparent medium of refractive index 8.4 into the Perspex as shown below:\r\nTransparent material \r\n C\r\nCalculate the critical angle C. \t\r\np?m= sin C/sin 900 = p?a*a?m=(1/a?p)*a?m\r\n =1/8.4 *1.48=1.48/8.4\r\nC= sin-1(1.48sin900/8.4) =38.070.\r\n8.8.1: Effects of total internal reflection \r\n • Mirage \r\nOn a hot day, the air above the ground is at a higher temperature than the layers above it. Thus the density of air increases with height above the ground. Denser air is optically denser than lighter one. Hence, a ray of light from the sun undergoes continuous refraction at the boundaries between any two layers of air with different temperatures. In each case, the ray bends away from the normal until the critical angle is achieved. Thereafter, the ray undergoes total internal reflection. An inverted image in the form of a pool of water is observed. This phenomenon is referred to as mirage. \r\nGenerally, mirage occurs as a result of continuous and progressive refraction at the air boundaries and total internal reflection. Mirage also occurs in cold regions but this time the ray of light curves upwards. \r\n\r\n\r\n\r\n\r\n\r\n\r\n\tI\r\n • Atmospheric refraction\r\nThe sun is sometimes seen before it actually rises or after it has set. This is because the light from the sun is refracted by the atmosphere towards the earth. (Recall: the earth is spherical).\r\n8.8.2: Applications of total internal reflection\r\n a) A prism periscope\r\nIt makes use of two right-angled isosceles prisms. The light from the object is inverted through 900 by the first prism and a further 900 by the second prism. \r\n\r\n\to\r\n\r\n\r\n\tI\r\nThis periscope produces brighter images compared to those of the simple periscope in which a plane is used. The image formed is erect and virtual. A prism periscope has the following advantages over the simple periscope:\r\n • Forms brighter and clearer images. A simple periscope produces many faint images besides the main image especially if the mirror is thick.\r\n • Does not absorb the energy of the light. Plane mirrors absorb some light incident on them.\r\n • Has a tough structure and thus does not easily wear. The painting on the plane mirror can wear out with time. \r\n b) A prism binoculars\r\nThis device is used to reduce the distance between the eyepiece and the objective thereby reducing the length of the telescope. It forms an erect image.\r\nObjective lenses\r\n\r\n\r\n\r\n\r\n\t\r\nEyepiece lenses\r\n\r\n\r\n c) Optical fibre\r\nIt is a thin flexible glass rod made up of two parts; the inner part made of glass of higher refractive index and the outer glass coating of lower refractive index. When a ray of light enters the fibre at an angle greater than the critical angle, it undergoes a series of total internal reflection before it finally emerges from the other end. None of the light energy is lost in the process. \r\nOptical fibres are used in medicine for viewing internal body organs (the endoscope) as well as in telecommunication. They are preferred to ordinary cables because they are light and thin and do not cause scattering of the signals.\r\n\r\n\r\n\r\n\r\n8.7: Dispersion of light \r\nWhite light from the sun is made up of seven colours. They all travel with the same velocity in vacuum but their velocities vary in other transparent media like glass and water. Hence when a ray of white light travels from a vacuum into a glass prism, it is separated into its component colours ranging from red, orange, yellow, green, blue, indigo to violet. The spreading out of light into its constituent colours by another medium is called dispersion. \r\nPure light is called monochromatic light while an impure light like white light is referred to as non-monochromatic or composite light. Dispersion of light is illustrated by the diagram below:\r\nGlass prism\r\n\r\n\tWhite light R\r\n V\r\n\r\nRed is least deviated while violet is the most deviated ray. Hence red light has the greatest velocity and violet the least velocity in glass. The coloured band produced is called a visible spectrum. The spectrum produced above is impure. In order to obtain a pure spectrum where each colour is distinct, an achromatic lens is placed between the screen and the prism. \r\nWhen the seven sevencolours are recombined, a white light is obtained. This can be achieved by using a similar but an inverted prism.\r\nWhite light\r\nR \r\n White light V\r\n\r\n8.8: The rainbow\r\nWhen a ray of light passes through a water drop, a rainbow is produced. The water disperses the light into its constituent colours. Each colour then undergoes total internal reflection within the drop before it eventually emerges into air again. \r\n\r\nWhite light\r\n\r\n\r\n\tV R\r\n\r\n\r\n\r\n\r\nTOPIC 9.: WAVES\r\n9.1: Introduction\r\n9.2: Properties of waves(form three)\r\nWave properties refer to the behaviour of waves under certain conditions. They include reflection, refraction, diffraction and interference among others. They can be investigated using a ripple tank which consists of a transparent tray containing water, a lamp for illumination, a white screen underneath and an electric motor (a vibrator). The motor is connected to a straight bar which produces straight waves. If circular waves are required, the bar is raised and a small spherical ball fitted to it to produce circular waves. To view the waves with ease, a stroboscope is used. A stroboscope is a disc having equally spaced slits. It is rotated and its speed controlled such that the waves appear stationary i.e frozen.\r\n9.8.1: Reflection of waves\r\nAll waves undergo reflection. It is the bouncing back of waves when they hit an obstacle. All waves undergoing reflection obey the laws of reflection as earlier stated.\r\n\r\n\r\ni0 r0\r\nNote that the wavelength of the waves remains unchanged. The pattern of the reflected waves depends on the shape of the incident waves and the reflector. Below are some patterns:\r\na) Plane waves incident on a straight reflector\r\nIncident wavefronts\r\n\r\n\r\n\r\n\r\nReflected waves\r\nb) Plane waves incident on a concave reflector\r\nIncident waves\r\n\r\n F\r\n\r\n\r\nReflected waves\r\nThe waves converge at the ", "contactno": "Total internal reflection, critical angle and refractive index", "education": "Theory", "email": "Total internal reflection, critical angle and refractive index", "gender": "Biology", "name": "REFRACTION OF LIGHT" }, { "Answer": "", "Citation": "", "Form": "Two", "Metadata": "", "Notes": "Notes", "Topicx": "1", "address": "A naturally occurring material known as lodestone, a form of iron ore, attracts\r\nsome materials when they are brought near it. When a bar of lodestone is\r\nsuspended freely, it settles in the north-south direction. This property of\r\nlodestone has been used to make the present-day magnets.\r\nMagnets attract certain materials known as magnetic materials, examples of\r\nwhich are iron, nickel, cobalt and their alloys. Magnets are made from these\r\nmagnetic materials.", "contactno": "Magnetism", "education": "Theory", "email": "Chapter 1 Magnetism", "gender": "Biology", "name": "Chapter 1 Magnetism" }, { "Answer": "", "Citation": "", "Form": "Two", "Metadata": "", "Notes": "Notes", "Topicx": "1", "address": "An object which is attracted by a magnet is a magnetic material. An object\r\nwhich is not attracted by a magnet is a nonmagnetic material. Metals such as\r\ncobalt, iron and nickel together with their alloys which are strongly attracted by\r\na magnet are called ferromagnetic materials.\r\nSome examples of non-magnetic materials are copper, brass, aluminium,\r\nwood and glass.", "contactno": "Magnetism", "education": "Theory", "email": "Properties of Magnets", "gender": "Biology", "name": " Magnetism" }, { "Answer": "ww", "Citation": "ww", "Form": "Two", "Metadata": "s", "Notes": "Notes", "Topicx": "0", "address": "ss", "contactno": "s", "education": "Theory", "email": "ww", "gender": "Biology", "name": "Magnetism" }, { "Answer": "ww", "Citation": "ww", "Form": "Two", "Metadata": "s", "Notes": "Notes", "Topicx": "0", "address": "ss", "contactno": "s", "education": "Theory", "email": "ww", "gender": "Biology", "name": "Magnetism" }, { "Answer": "ww", "Citation": "ww", "Form": "Two", "Metadata": "s", "Notes": "Notes", "Topicx": "0", "address": "ss", "contactno": "s", "education": "Theory", "email": "ww", "gender": "Biology", "name": "Magnetism" }, { "Answer": "ww", "Citation": "ww", "Form": "Two", "Metadata": "s", "Notes": "Notes", "Topicx": "0", "address": "ss", "contactno": "s", "education": "Theory", "email": "ww", "gender": "Biology", "name": "Magnetism" }, { "Answer": "ww", "Citation": "ww", "Form": "Two", "Metadata": "s", "Notes": "Notes", "Topicx": "0", "address": "ss", "contactno": "s", "education": "Theory", "email": "ww", "gender": "Biology", "name": "Magnetism" }, { "Answer": "ww", "Citation": "ww", "Form": "Two", "Metadata": "s", "Notes": "Notes", "Topicx": "0", "address": "ss", "contactno": "s", "education": "Theory", "email": "ww", "gender": "Biology", "name": "Magnetism" }, { "Answer": "ww", "Citation": "ww", "Form": "Two", "Metadata": "s", "Notes": "Notes", "Topicx": "0", "address": "ss", "contactno": "s", "education": "Theory", "email": "ww", "gender": "Biology", "name": "Magnetism" }, { "Answer": "fyt", "Citation": "jeff obiero UON", "Form": "Two", "Metadata": "jeff obiero UON, Engineering, Faculty Member", "Notes": "Notes", "Topicx": "1", "address": "yguygyu", "contactno": "Newton’s third law", "education": "Theory", "email": "Machines", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Unknown", "Form": "Two", "Metadata": "Unknown", "Notes": "Notes", "Topicx": "1", "address": "Magnets are substances that are able to attract and hold items. Lodestone is the only known\r\nnatural magnet which was discovered by the Chinese 2,000 years ago. Other magnets produced\r\nartificially by man are called artificial magnets.", "contactno": "Magnetism", "education": "Theory", "email": "Introduction", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Unknown", "Form": "Two", "Metadata": "Unknown", "Notes": "Notes", "Topicx": "1", "address": "Magnetic materials are those that are strongly attracted by magnets while non-magnetic\r\nones are those that are not affected by magnets. Iron, steel, cobalt and nickel are magnetic\r\nsubstances, while wood, glass and copper are examples of non-magnetic substances.\r\nSubstances that are repelled by magnets are said to be diamagnetic whereas those which are\r\nstrongly attracted i.e. iron, nickel, cobalt are called ferromagnetic materials. The materials\r\nthat are so lightly attracted such that the magnet seems to have no effect on them are called\r\nparamagnetic materials (mostly non-magnetic materials). Ferrites are a mixture of iron oxide\r\nand barium oxide are the most newly developed magnetic materials. Ceramic magnets or\r\nmagnadur magnets are made from ferrites and are very strong.", "contactno": "Magnets and non-magnetic materials", "education": "Theory", "email": "Magnets and non-magnetic materials", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": " 1. They are double poled substances with both the North and South poles.\r\n 2. Like poles repel and unlike poles attract. Repulsion is a sure method of determining whether two substances are magnets.\r\n 3. The greatest magnetic force is concentrated around the poles of a magnet.", "contactno": "Properties of magnets", "education": "Theory", "email": "Properties of magnets", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "Magnetic field is the space around a magnet where magnetic field (force) is observed.", "contactno": "Magnetic field patterns.", "education": "Theory", "email": "Magnetic field patterns.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "A line of force gives the direction of the magnetic field at each point along it. Their closeness is a measure of the strength of the magnetic field or of the force that would be exerted by the bar magnet.", "contactno": "Plotting field patterns", "education": "Theory", "email": "Plotting field patterns", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "The following are methods used to make magnets.\r\n a) Magnetic induction – this is a process by which magnets are made by placing ferromagnetic materials in a magnetic field. Materials like iron lose their magnetism easily and are said to be soft while others like steel gain magnetism slowly but retain it longer and are therefore said to be hard and are used to make permanent magnets.\r\n b) Magnetizing by stroking – the object to be magnetized is placed on a bench then a bar magnet is dragged along the length of the bar from one end to the other. This is repeated several times and the object becomes magnetized. This method is known as\r\nsingle -stroke method", "contactno": "Making magnets", "education": "Theory", "email": "Making magnets", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "Magnetizing using an electric current – this is the use of magnetic effect of an electric current through a solenoid (insulated wire of many turns).", "contactno": "Magnetizing using an electric current – this is the use of magnetic effect of an electric current th", "education": "Theory", "email": "Magnets and non-magnetic materials", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "Demagnetizing is the process of removing magnetic properties of a magnet. The following methods are which a magnet can lose its magnetism;\r\n a) Hammering them hard with their poles facing E-W direction\r\n b) Heating them strongly\r\n c) Placing a magnet inside a solenoid and passing an a.c. current through it for a short time.", "contactno": "Demagnetizing", "education": "Theory", "email": "Demagnetizing", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": " a) Magnets should be stored in pairs with unlike poles adjacent to each other attached to pieces of soft iron called keepers.\r\n b) Magnets should not be hammered especially with their poles facing E-W direction.\r\n c) Magnets should not be heated strongly or dropped roughly on hard surfaces.\r\n d) Magnets should not be placed near alternating currents.\r\n e) Magnets should be kept dry and clean since rust can make them lose their magnetism.", "contactno": "Caring for magnets", "education": "Theory", "email": "Caring for magnets", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": " 1. Used in making other magnets\r\n 2. Used in making loud speakers\r\n 3. Used in making moving coil meters 4. Used in making telephone speakers.", "contactno": "Uses of magnets", "education": "Theory", "email": "Uses of magnets", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "In ferromagnetic substances small atomic magnets form large groups called domains. These atomic magnets face one direction where the direction varies from one domain to another. In an un-magnetized crystal the directions of these domains are different hence their resultant magnetism is zero.\r\n\r\nWhen a magnetic material is placed in a magnetic field the atomic magnets rotate and eventually all domains face the same direction. When this happens then the material becomes magnetized. When a material is magnetized we say it is saturated. This means that the magnetism of the material cannot be increased by any other method and this is the domain theory of magnetism.", "contactno": "Domain theory of magnetism.", "education": "Theory", "email": "Domain theory of magnetism.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "2", "address": "Vernier callipers is used when higher accuracy in measurement is required and this cannot be done using a metre rule.\r\nVernier callipers has two scales; main scale and vernier scale. Outside jaws are used to measure both lengths and external diameters, inside jaws for measuring internal diameters while the tail is used for measuring depths of cavities. The main scale is divided into cm and mm. The vernier scale is divided into 10 equal divisions of 0.9 mm each. The accuracy of vernier callipers is 0.10 mm.", "contactno": "Measuring length using vernier callipers.", "education": "Theory", "email": "Measuring length using vernier callipers.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "It is a device used to measure small lengths. It has an accuracy of 0.01 mm. It has two scales; the sleeve scale and thimble scale. The sleeve scale is divided into upper and lower scales with the upper division in mm and lower divisions in 0.5 mm. Thimble scale is divided into 50 equal divisions each division consisting of 0.01 mm.\r\n\r\n\r\n\r\n\r\n\r\nThe reading is taken in two steps;\r\n a) The reading on the sleeve scale is read ta the point where it touches the edge of the thimble in mm and half mm.\r\n b) The thimble scale is read at the point where the centre line of the sleeve is parallel to the thimble scale division.\r\nExamples\r\n 1. Give the reading in the following.\r\n\r\nSolution\r\nSleeve reading –\t3.5 mm Thimble reading – 0.45 mm Adding up we get 3.95 mm.\r\n\r\n 2. What is the reading in the following micrometer screw gauge?\r\n\r\nSolution\r\nSleeve scale reading – 4.0 mm Thimble scale reading - 0. 32 mm\r\nAdding up the two we get 4.32 mm.\r\nCalculating the size of a molecule.\r\nBoth the volume and area of a drop can be calculated using the following formulas Volume\r\n= 4/3 ?r3 and Area = ?r2h.\r\nExamples\r\n 1. A drop of olive oil, whose volume is 0.12 mm3, was placed on a surface of clean water.\r\nThe oil spread and formed a patch of area 6.0 × 104 mm2. Estimate the size of the olive oil.\r\nSolution\r\nVolume = 0.12 mm3. Area of the oil patch = 6.0 × 104 mm2. Volume = area × thickness of the patch, therefore Thickness of the oil patch = volume / area = 0.12 / 6.0 × 104 = 2.0 × 10-6 mm or 2.0 × 10-9 m.\r\n 2. Suppose an oil drop has a volume of 0.10 mm3 and forms a film with a radius of 10 cm. Calculate, the thickness of the oil film.\r\nSolution\r\nArea of the film = ?r2 = 3.14 × 10 × 10 = 314 cm2 = 31,400 mm2.\r\nThickness of the oil film = volume / area, hence 0.10 / 31,400 = 3.0 × 10-6 mm. (The thickness of the oil film is called upper limit to the size of molecule because the molecule cannot be bigger than the thickness of the oil film)", "contactno": "Micrometer screw gauge", "education": "Theory", "email": "Micrometer screw gauge", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "It is a device used to measure small lengths. It has an accuracy of 0.01 mm. It has two scales; the sleeve scale and thimble scale. The sleeve scale is divided into upper and lower scales with the upper division in mm and lower divisions in 0.5 mm. Thimble scale is divided into 50 equal divisions each division consisting of 0.01 mm.\r\n\r\n\r\n\r\n\r\n\r\nThe reading is taken in two steps;\r\n a) The reading on the sleeve scale is read ta the point where it touches the edge of the thimble in mm and half mm.\r\n b) The thimble scale is read at the point where the centre line of the sleeve is parallel to the thimble scale division.\r\nExamples\r\n 1. Give the reading in the following.\r\n\r\nSolution\r\nSleeve reading –\t3.5 mm Thimble reading – 0.45 mm Adding up we get 3.95 mm.\r\n\r\n 2. What is the reading in the following micrometer screw gauge?\r\n\r\nSolution\r\nSleeve scale reading – 4.0 mm Thimble scale reading - 0. 32 mm\r\nAdding up the two we get 4.32 mm.\r\nCalculating the size of a molecule.\r\nBoth the volume and area of a drop can be calculated using the following formulas Volume\r\n= 4/3 ?r3 and Area = ?r2h.\r\nExamples\r\n 1. A drop of olive oil, whose volume is 0.12 mm3, was placed on a surface of clean water.\r\nThe oil spread and formed a patch of area 6.0 × 104 mm2. Estimate the size of the olive oil.\r\nSolution\r\nVolume = 0.12 mm3. Area of the oil patch = 6.0 × 104 mm2. Volume = area × thickness of the patch, therefore Thickness of the oil patch = volume / area = 0.12 / 6.0 × 104 = 2.0 × 10-6 mm or 2.0 × 10-9 m.\r\n 2. Suppose an oil drop has a volume of 0.10 mm3 and forms a film with a radius of 10 cm. Calculate, the thickness of the oil film.\r\nSolution\r\nArea of the film = ?r2 = 3.14 × 10 × 10 = 314 cm2 = 31,400 mm2.\r\nThickness of the oil film = volume / area, hence 0.10 / 31,400 = 3.0 × 10-6 mm. (The thickness of the oil film is called upper limit to the size of molecule because the molecule cannot be bigger than the thickness of the oil film)", "contactno": "Micrometer screw gauge", "education": "Theory", "email": "Micrometer screw gauge", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "The turning effect of a body is called the moment of that force. The turning effect produced depends on both the size of the force and the distance from the pivot.\r\nThe moment of a force about a point is the product of the force applied and the perpendicular distance from the pivot (or turning point) to the line of action of the force. Hence, Moments of a force = Force × perpendicular distance from pivot.", "contactno": "Turning effects", "education": "Theory", "email": "Turning effects", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "The law of moments states that “when a body is in balance or in equilibrium, the sum of the clockwise moments equals the sum of anti-clockwise moments”. The SI units of the moments of a force is Newton metre (Nm).", "contactno": "The law of moments", "education": "Theory", "email": "The law of moments", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "A lever is any device which can turn about a pivot or fulcrum. The applied force is called the effort and is used to overcome the resisting force called the load. We use the law of moments in the operation of levers.", "contactno": "The lever", "education": "Theory", "email": "The lever", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "A lever is any device which can turn about a pivot or fulcrum. The applied force is called the effort and is used to overcome the resisting force called the load. We use the law of moments in the operation of levers.", "contactno": "The lever", "education": "Theory", "email": "The lever", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "Centre of gravity or C.G is the point of balance of a body in which the total weight of the body seems to act through. For regular shaped bodies the C.G is at the geometric centre of the body. For irregular bodies their weight still acts at the centre of the gravity and the law of moments can be used to determine the weight of the body.", "contactno": "EQUILIBRIUM AND CENTRE OF GRAVITY.", "education": "Theory", "email": "Centre of gravity", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "For a body to be in equilibrium (neither moving nor rotating), under the action of parallel forces, the following conditions will be satisfied;\r\n a) The sum of upward forces must be equal to the sum of downward forces.\r\n b) The sum of clockwise moments equals the sum of anticlockwise moments. The two are called the first and second condition of equilibrium respectively.", "contactno": "Parallel forces and equilibrium", "education": "Theory", "email": "Parallel forces and equilibrium", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "This is a term which explains how easy or difficult it is for an object to topple over when a force is applied to it. Factors affecting stability,\r\n a) Base area – the bigger the base area the more the stability.\r\n b) Position of the centre of gravity – the higher the centre of gravity the less stable the body will be.\r\nStates of equilibrium\r\n 1. Stable equilibrium – if a body is displaced by a small amount of force it returns to its original position.\r\n 2. Unstable equilibrium – if a body is displaced by a small amount of force it toppled over and does not return to its original position.\r\n 3. Neutral equilibrium – a body is at rest in whichever position it is placed in i.e. it does not rise or fall when displaced.", "contactno": "Stability", "education": "Theory", "email": "Stability", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "This is a term which explains how easy or difficult it is for an object to topple over when a force is applied to it. Factors affecting stability,\r\n a) Base area – the bigger the base area the more the stability.\r\n b) Position of the centre of gravity – the higher the centre of gravity the less stable the body will be.\r\nStates of equilibrium\r\n 1. Stable equilibrium – if a body is displaced by a small amount of force it returns to its original position.\r\n 2. Unstable equilibrium – if a body is displaced by a small amount of force it toppled over and does not return to its original position.\r\n 3. Neutral equilibrium – a body is at rest in whichever position it is placed in i.e. it does not rise or fall when displaced.", "contactno": "Stability", "education": "Theory", "email": "Stability", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "They are also known as spherical mirrors and are formed when a spherical glass is silvered. If the inside is silvered a convex or diverging is formed while a concave or converging mirror is formed when the outside is silvered.", "contactno": "Concave and convex mirrors", "education": "Theory", "email": "Concave and convex mirrors", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": " 1. Centre of curvature (C) – this is the centre of the sphere of which the mirror is part of. The centre itself is called the pole (P).\r\n 2. Principal axis – this is the line joining the centre of curvature (C) to the pole (P).\r\n 3. Principal focus (F) – is a point on the principal axis through which a ray is reflected when it hits a concave mirror. In a convex mirror the ray is reflected and appears to originate from the point. F is virtual for a convex mirror while it is real for a concave mirror.\r\n 4. Radius of curvature (r) - this is the distance from the pole to the centre of curvature. The distance from the pole to the principal focus is called the focal length (f).", "contactno": "Parts of a spherical mirror.", "education": "Theory", "email": "Parts of a spherical mirror.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "They produce a wide parallel beam or converge a large beam of light to a point. They are widely used in making car headlights or in spotlights.", "contactno": "Parabolic mirrors.", "education": "Theory", "email": "Parabolic mirrors.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "Location of images using ray diagrams.\r\nWhen drawing ray diagrams the following symbols are used to represent the mirrors.\r\n\r\nThe image is located by drawing any two of the following rays:\r\n i) A ray parallel to the principal axis which is reflected through the principal focus.\r\n ii) A ray through the centre of curvature which is reflected along its own path since it hits\r\nthe mirror normally.\r\n iii) A ray through the principal focus which is reflected parallel to the principal axis.\r\n\r\nVirtual images are formed when rays diverge and as such the rays are extended backwards using dotted line till they meet. The image formed is also dotted since it is not formed by an intersection of real rays. A real image is formed by intersection of real rays. Concave mirror.", "contactno": "Images formed by spherical mirrors.", "education": "Theory", "email": "Images formed by spherical mirrors.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "Image is always formed behind the mirror. It is virtual, erect and always diminished.", "contactno": "Convex mirror.", "education": "Theory", "email": "Convex mirror.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": " a) They are used in satellite dishes.\r\n b) They are used in making shaving mirrors.\r\n c) They are used in telescopes.\r\n d) They are used in driving mirrors.", "contactno": "Applications of curved reflectors.", "education": "Theory", "email": "Applications of curved reflectors.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "Magnification is the ratio of the image size to the object size. Magnification (M) = height of the image / height of the object.\r\nWhen the ratio is greater than one we say the image is magnified and when less than one we say it is diminished.\r\nAlso magnification = image distance from the mirror / object distance from the mirror. ", "contactno": "Magnification.", "education": "Theory", "email": "Magnification.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "Solution\r\nLet 1 cm represent 5 cm. Then the focal length is 3 cm. Object distance = 7 cm, object height = 1 cm.\r\n\r\n\r\n\r\n\r\n\r\n\r\nFrom the scale drawing,\r\nImage position = 5.4 cm × 5 = 27 cm in front of the mirror. Image size = 0.75 cm × 5 = 3.75 cm.\r\nImage is real and inverted.", "Citation": "Public", "Form": "Two", "Metadata": "Unknown", "Notes": "Question", "Topicx": "1", "address": " Determine the size, position and nature of the image of an object 5.0 cm tall, placed on\r\nthe principal axis of a concave mirror of focal length 15 cm, at a distance 35 cm from the mirror.", "contactno": "Reflection", "education": "Problem", "email": "Reflection", "gender": "Biology", "name": "Magnetism" }, { "Answer": "Let 1 cm represent 5 cm, then the focal length = 3 cm, object size = 1 cm Object distance = 2 cm.\r\n\r\n\r\nFrom the scale drawing,\r\nImage position = 1.2 cm × 5 = 6.0 cm behind the mirror. Image size = 0.6 cm × 5 = 3.0 cm. The image is virtual and erect.\r\nMagnification = image dist. / object dist. Hence 6 /10 = 0.6 (diminished).\r\n", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "A vertical object 5 cm high is placed 10 cm in front of a convex mirror of focal length 15 cm. find the position, size and nature of image formed. Determine the magnification of the image.", "contactno": "Reflection", "education": "Problem", "email": "Reflection", "gender": "Biology", "name": "Magnetism" }, { "Answer": "Let 1 cm represent 5 cm, then the focal length = 3 cm, object size = 1 cm Object distance = 2 cm.\r\n\r\n\r\nFrom the scale drawing,\r\nImage position = 1.2 cm × 5 = 6.0 cm behind the mirror. Image size = 0.6 cm × 5 = 3.0 cm. The image is virtual and erect.\r\nMagnification = image dist. / object dist. Hence 6 /10 = 0.6 (diminished).\r\n", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "A vertical object 5 cm high is placed 10 cm in front of a convex mirror of focal length 15 cm. find the position, size and nature of image formed. Determine the magnification of the image.", "contactno": "Reflection", "education": "Problem", "email": "Reflection", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "Hans Christian Oersted discovered the magnetic effect of a current in 1819. The direction of the field is dependent on the direction of the current. This discovery brought about the development of electric bells, electric motors, telephone receivers and radios.", "contactno": "MAGNETIC EFFECT OF AN ELECTRIC CURRENT.", "education": "Theory", "email": "Introduction: Oersted’s discovery.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "The direction of the lines of force can be determined using a simple rule called the right-hand screw rule. This rule states that “if a right-hand screw advances in the direction of the current, then the rotation of the screw is in the direction of the field”. Another rule is the right-hand grip rule which states that “if the wire carrying a current is gripped with the right hand, using the thumb along the conductor and pointing in the direction of the current, then the direction of curled fingers is in the direction of the lines of force”.\r\n\r\n", "contactno": "Determining the direction of the lines of force.", "education": "Theory", "email": "Determining the direction of the lines of force.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "A solenoid is a cylindrical coil of wire acting as a magnet when carrying electric current.\r\nThe direction of the field can be determined using a simple rule stated as follows “if the coil (solenoid) is viewed from one end and the current flows in an anticlockwise direction at that end, then that end is the North Pole. If the current flows in a clockwise direction, then that end is the South Pole”.", "contactno": "Magnetic field due to a solenoid. The rule for polarity.", "education": "Theory", "email": "Magnetic field due to a solenoid. The rule for polarity.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "An electromagnet is a soft metal core made into a magnet by passing an electric current through a coil surrounding it. They only maintain their magnetism if current continues to flow, if switched off they lose their magnetism.", "contactno": "Electromagnets.", "education": "Theory", "email": "Electromagnets.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": " 1. Increasing current through the coil.\r\n 2. Increasing the number of turns of the coil.\r\n 3. Using iron of C- core shape which brings both magnetic poles together.", "contactno": "Factors affecting the strength of an electromagnet.", "education": "Theory", "email": "Factors affecting the strength of an electromagnet.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "When the switch is closed the current passing through the solenoids magnetizes them and they pull the soft iron armature which makes the hammer hit the gong therefore producing sound. When the hammer hits the gong the contact between the spring and the screw is broken and then stops the current from flowing. The soft iron core loses its magnetism and releases the armature which is then pulled back by the screw. The contact between the spring and the screw is regained and the process repeats itself again and again therefore the gong is struck continuously.", "contactno": "Electric bell", "education": "Theory", "email": "Some applications of electromagnets.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "It consists of a u-magnet made by attaching two soft-iron bars to the end of a short permanent magnet. The solenoids are wound in opposite directions around the bars. When the phone is lifted the current flows through the solenoids depending on the microphone on the other end of the line. These varying current spasms induce magnetism of varying strengths in the iron bars which in turn causes the magnetic alloy diaphragm to vibrate differently producing sound.", "contactno": "Electric bell", "education": "Theory", "email": "Some applications of electromagnets.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "When a conductor carries a current in a magnetic field a force acts on it. The direction of the force depends on the directions of the field and current.\r\nThe factors affecting the magnitude of the force are;\r\n a) The current flowing in the conductor\r\n b) The strength of the magnet\r\n c) The length of the conductor in the magnetic field.\r\nThe relationship between the directions of the current, field and force are mutually perpendicular. They are summarized in a law called Fleming’s right-hand rule or the motor rule. This rule states that “if you hold the first finger, the second finger and the thumb of your left hand mutually perpendicular to each other, so that the first finger points in the direction of the magnetic field and the second finger points in the direction of the current in the conductor, then the thumb points in the direction of the force acting on the conductor”.", "contactno": "Force on a current-carrying conductor in a magnetic field.", "education": "Theory", "email": "Force on a current-carrying conductor in a magnetic field.", "gender": "Biology", "name": "Magnetism" }, { "Answer": "", "Citation": "Public", "Form": "Two", "Metadata": "Public", "Notes": "Notes", "Topicx": "1", "address": "Consists of a rectangular coil of wire mounted on an axle which can rotate between the poles of a magnet. For the rotation to be continuous the ends of the coil is connected to half-rings called the split-ring commutators. The battery terminals are attached to brushes which slide on these half-rings. D.C motors are useful as car starter motors, hand drills, machine motors, fans etc.", "contactno": "Simple D.C motor.", "education": "Theory", "email": "Applications of the force on a conductor.", "gender": "Biology", "name": "Magnetism" } ]