2 Energy is the ability to do work or cause change What is Energy 5.1Energy is the ability to do work or cause changeWork is done when a force moves an object through a distance.W = F x D
3 Work and EnergyWhen an object or living thing does work on another object, some of its energy is transferred to that objectTherefore: Work can be thought of as the transfer of energy.When energy is transferred, the object upon which the work is done gains energy.Energy is measured in Joules (same unit as work)
4 Power and Energy Power is the rate at which work is done If the transfer of energy is work, then power is the rate at which energy is transferred OR the amount of energy transferred in one unit of timePower = Energy transferredTime
5 Power & Energy Power is involved whenever energy is being transferred. Calm breeze vs. TornadoPower of both is the rate of energy transfer to lift a leaf a certain distanceTornado has the same energy transfer, but with more power because it transfers the energy at a quicker rate.
6 Types of Energy Two basic types of energy Kinetic Potential Type of energy depends on if the object is moving or not.A moving object can do work when it strikes another object and moves it some distanceThe energy an object has due to its motion is called kinetic energyGreek word kinetos = moving
7 Factors affecting Kinetic Energy (KE) Kinetic energy depends onMassVelocityKE increases as mass increasesKE increases as velocity increases
8 Calculating KE KE = ½ x mass x velocity 2 Does changing the mass and velocity have the same affect on KE?NO – changing the velocity has a greater effect on KE than changing the mass by the same factor.WHY? – because velocity is squared.Therefore, doubling the mass will double the KE, but doubling the velocity will quadruple the KE.
9 Potential Energy (PE)An object does not have to be moving to have energySome objects have stored energyResult of their shapes or positionsLift a book off the floor to your deskCompress a spring to wind a toy.Energy has been transferred to those objects in both examples and is stored.May be used later when the book falls to the floor or the spring unwinds.Stored energy as a result of shape or position of an object is potential energy.This type of energy has the “potential” to do work.
10 Gravitational Potential Energy (GPE) Defined as potential energy related to an objects height.GPE equaled to the work done to lift the objectRecall: work = force x distanceThe force used to lift the object equals the weight of the objectThe distance the object is moved is the object’s height
11 Gravitational Potential Energy (GPE) Formula to calculate GPEGPE = mass x gravity x heightSimplified as GPE = weight x heightREMEMBER: weight = mass x force of gravityGravity On Earth = 9.8 m/s2
13 CalculateIf the ski jump is 40m high, what is the GPE of theGreen skier = 600NRed Skier = 500N500 Newtons x 40m = 20,000 J GPE600 Newtons x 40m = 24,000 J GPE
14 Elastic Potential Energy (EPE) An object gains a different type of potential energy when it is stretchedElastic potential energy – the potential energy associated with objects that can be stretched or compressed
15 Formula to calculate Elastic potential energy EPE = ½ kx2
16 Chapter 5-2 Forms of Energy Energy comes in many formsMechanical energy – associated with the position and motion of an objectA combination of potential and kineticCalculation:Mechanical Energy = Kinetic energy + Potential Energy
17 Example of ME calculation A football thrown by a quarterback has BOTH PE and KE. The higher the ball is thrown the greater the PE, the faster it is thrown the greater the KE.PE = 32JKE = 45 JMechanical Energy (ME) = 77J (32+45)An object with mechanical energy can do work on another objectMechanical energy is the ability to do work.The more ME an object has the more work it can do.
18 Other forms of energyThese other forms are associated with the particles that make up objects.These particles are too small to be seen. (atoms & molecules)Thermal energyElectrical energyChemical energyNuclear energyElectromagnetic energy
19 Thermal energyAll objects are made up of atoms and moleculesAtoms and molecules are in constant motion – therefore they have kinetic energyAtoms and molecules are arranged differently in different objects – therefore they have potential energy
20 Thermal EnergyTotal PE and KE of particles in a substance = thermal energyExample Melting ice creamFast moving particles in warm air, make the particles in the ice cream move faster, as the kinetic energy of the ice cream particles increases, the thermal energy increases. The ice cream melts.
21 The energy of electric charges Electrical energyThe energy of electric chargesDepending on whether the charges are stored or moving, EE can be kinetic or potential.
22 Almost everything is made up of chemical compounds Chemical EnergyAlmost everything is made up of chemical compoundsChemical compounds are made up of atoms and moleculesBonds between the atoms and molecules hold the compounds togetherThese chemical bonds have energy
23 Chemical EnergyCE is the energy stored within the chemical bonds of substances.Food we eatMatchesCells in our bodyWhen bonds break, chemical energy is released and new compounds may form
24 Nuclear Energy A type of potential energy Stored in the nucleus of an atomReleased during a nuclear reactionNuclear fission – occurs when a nucleus of an atom is splitUsed in nuclear power plants
25 Nuclear EnergyNuclear fusion – occurs when the nuclei of atoms join togetherOccur continuously in the sun, release tremendous amounts of energy
26 Electromagnetic Energy Sunlight is a form of Electromagnetic energyTravels in wavesEM waves have both electrical and magnetic propertiesExamplesMicrowavesX-raysUV radiationInfrared radiationRadio waves
27 5.3 Energy Transformation and Conservation Niagara FallsA center for a network of electrical power linesWater above the falls is used to generate electricity.
28 Energy Transformations The mechanical energy of moving water can be transformed into electrical energy.Most forms of energy can be transformed into other forms of energy.A change from one for of energy to another is called: energy transformation
30 Multiple Transformations Often a series of transformations are needed to do workA matchMechanical - Thermal - Chemical - Thermal - ElectromagneticThe ME used to strike the match is transformed into TE. TE causes the particles in the match to release stored chemical energy, which is transformed into TE and the EME seen as light.
31 Multiple Transformations A car engineEE produces a spark- TE of spark -> releases CE in fuel - CE turns into TE - TE converted into ME & EE
32 Transformations between Potential and Kinetic Energy Transformation between Potential energy and Kinetic energy is the most common form of transformation.Any object that rises and falls experiences a change in its kinetic and gravitational potential energy.
33 Energy transformation in juggling No motion at its highest point, no KE, maximum PEDecreasing KE as it risesPE decreasing, Rising KEIn motion = KEHigh KENo motion = no KE, ball has PE
34 Energy transformation in a pendulum Pendulum continuously transforms energy from kinetic to potential and back.
35 Conservation of Energy The law of conservation of energy states:When one form of energy is transformed to another, no energy is destroyed in the process. Energy cannot be created or destroyedThe total amount energy is the same before and after any transformation. If you add up all the new forms of energy after a transformation, all the original energy will be accounted for.
36 Energy and frictionScenario: If you set a spinning top in motion, will it stay in motion forever?WHY?As the top spins, in encounters friction with the surface it is spinning on and with the air.Whenever a moving object experiences friction, some of the KE is transformed into TE.The fact that friction transforms mechanical energy into thermal energy explains why no machine is 100% efficient.Output work is always less than input work in a real machine.
37 Energy and matter Albert Einstein’s Theory of Relativity During some nuclear reactions, matter is converted to energy.Einstein showed that energy and mass are equivalent and can be converted into one another.E = mc2 is the equation to calculate the amount of energy that is created when matter is destroyed.Matter = anything that has mass and takes up space
38 5.4 Energy and Fossil Fuels Earth 400 million years agoLush green swampy forestEnormous dragon fliesHuge cockroaches
39 Formation of Fossil Fuels Fuel – a material that contains stored potential energyEx. Gasoline used in cars, propane used in grillsFuels used today were formed hundreds of million of years ago.These fuels include:Coal, petroleum, and natural gasKnown as Fossil Fuels
40 Formation of Fossil Fuels Vast ancient forests were the source of coalWhen plants and animals died, their remains piled up in thick layers in swamps and marshesClay and sediment covered their remainOver time, increased pressure and temperature turned their remains into coal
41 Meaning: fuels do not create energy Fossil fuels store energy Energy from the sunEnergy is conservedMeaning: fuels do not create energyFossil fuels store energyWhere did they get the energy from?The sun
42 Energy from the sun Fossil fuels contain energy that came from the sun The sun is the source of energy for most of Earth’s processesWithin the dense core of the sun – the process of nuclear fusion –> nuclear energy is transformed into electromagnetic energy as well as other forms.Some of this electromagnetic energy reaches the Earth as light.
43 The Sun’s energy on Earth When the sun’s energy reaches earthPlants, algae, and certain bacteria - transform some of the light into chemical energySome of the energy in the chemical compounds they make is used for their daily needs. The rest is stored.
44 The Sun’s energy on Earth Animals eat plants – store some of the plants chemical energy in their cellsWhen the animals and plants died – some of the energy stored is trapped within themThis trapped energy is the chemical energy found in coal.
45 Burning fuels is known as combustion Use of Fossil FuelsFossil Fuels can be burned to release the chemical energy stored millions of years ago.Burning fuels is known as combustionDuring combustion, chemical energy is transformed to thermal energyThermal energy can heat water to produce steam.
46 Ex. Modern coal fired power plants: Steam is raised to a high temp in a boiler – leaves the boiler with high pressure – turns a turbineA turbine is a fan connected to an axle – steam causes the blades of the fan to turn very fast – thermal energy is converted to mechanical energy.Turbines are connected to generators that produce electricity.Chemical –> thermal –> mechanical -> electrical