22-Column Notes MAIN IDEA DETAILS What is Energy? The ability to do work or cause changeWork is the transfer of energyWhat is Kinetic Energy?Two kinds of energy are POTENTIAL and KINETICKinetic is energy of motionKinetic comes from the Greek word ‘Kinetos’ which means ‘Moving’
3Kinetic Energy - Motion Kinetic comes from the Greek word kinetos meaning ‘moving’.
42-Column Notes MAIN IDEA DETAILS How is Mass and Velocity Related to Kinetic Energy?Kinetic energy depends upon both mass and velocityMore mass requires less velocity to have same energyKinetic energy increases as mass increasesKinetic energy increases as velocity increases
52-Column Notes MAIN IDEA DETAILS How do we calculate Kinetic Energy? EK = (Mass x Velocity2 )/2
6Energy MAIN IDEA DETAILS What is Potential Energy? Potential energy is energy that is stored. It has the potential to do workEnergy that has to do with stretching or compressing objects is elastic potential energyEnergy that has to do with height is gravitational potential energy
7Calculating Potential Energy Gravitational Potential Energy =Weight X HeightWeight IS NOT MassWeight = Mass X Gravitational AccelerationSI Unit of measure for weight is ‘newton’.One ‘newton’ is the force required to accelerate on kg 1 m/s/sGravitational Acceleration = 9.8 m/s/sEnergy is measured in ‘joules’ = ‘newton-meter’
8Energy MAIN IDEA DETAILS (Continued) Gravitational Potential Energy = Weight x HeightEnergy is measured in joulesWeight = Mass x Gravitational AccelerationTherefore:EGP=Mass x Gravity x Height
9Energy MAIN IDEA DETAILS What are the different forms of Energy? Mechanical: motion or position of an objectThermal: Total energy in the particles of an objectChemical: Energy stored in chemical bondsElectrical: energy in moving electronsElectromagnetic: energy traveling in waves (light, sound)Nuclear: energy stored in nucleus of an atom
10Kinetic Energy - Motion Kinetic comes from the Greek word kinetos meaning ‘moving’.
11Potential Energy – Stored & Waiting The rock has potential to do work, or to move. This is ‘gravitational’ potential energy.Elastic potential energy is associated with objects that can stretch or be compressed (springs).Stored energy has the ‘Potential’ to do work
12Mechanical EnergyMechanical Energy is the energy associated with the motion or position of an object.
13Thermal Energy - HeatThe faster the molecules and electrons move, the more thermal energy it contains.All Atoms and Molecules are particles in motion. The faster they move, the more Thermal energy they have. The more thermal energy, the ‘hotter’ they are.
14Chemical Energy – Energy Stored in Chemical Bonds Chemical reactions give off or take in energy to create the chemical bonds. The energy stored in the chemical bonds is Chemical Energy and can be released by breaking the bonds
15Electrical EnergyElectrical Energy is the energy associated with moving electrical charges.
16Electromagnetic Energy - Light Electromagnetic energy is energy traveling in waves. This includes light and sound.
17Nuclear EnergyNuclear Energy is the energy that holds the nucleus of an atom together. ‘Splitting’ the nucleus is an atomic reaction that releases tremendous potential energy.
18Review Questions Are energy and work the same thing? No: Energy is the potential to do work. Work is done when energy is transferred from one object to anotherHow are kinetic and potential energy different?Kinetic is the energy of motion. Potential is stored energy.
19Review Questions - 2List the forms of energy and give an example of each:MechanicalCar movingThermal:Warm waterChemicalGasolineElectricalBatteryElectromagneticLightNuclearSun
20Review Questions - 3A boulder weighs 200N, poised at the edge of a 100M cliff. What is its gravitational potential energy? Draw a graph of its potential energy as it falls from 100M to 50M to 20M to 10MEGP=200N x 100M= 20,000JAt 50 M, = 200N x 50M = 10,000JAt 20 M, = 200N x 20M = 4000JAt 10 M, = 200N x 10M = 2000J
21Exercise – calculate your potential energy One Kg is 2.2 pounds at sea level.Your mass is your weight divided by 2.2Assume you are 1 meter above the floor, about the height of the desk.The gravitational acceleration constant is 9.8 m/s/s
23Energy Conversion and Conservation MAIN IDEADETAILSHow do conversions between forms of energy occur?Change from one form of energy to another is an energy conversionAny form of energy can be converted to any other form
24Energy Conversion & Conservation MAIN IDEADETAILSHow Does Kinetic and Potential Energy Convert?Potential to Kinetic and vice versa is most common conversion.What is the energy conversion in juggling?Object rising or falling is changing kinetic energy to/from Gravitational Potential EnergyWhat is the energy conversion in a Waterfall:At top of waterfall, water has potential energy. As it falls it is converted to kinetic energy.
25Energy Conversion and Conservation MAIN IDEADETAILSWhat is the energy conversion in a Pole Vault?Pole vaulter runs (kinetic). Plants pole which bends (elastic). Vaulter springs into the air (kinetic) which changes to height (gravitational potential). Vaulter falls (kinetic)What is the energy conversion in a pendulum?Continuous conversion between gravitational potential and kinetic. As it goes up, kinetic is converted to potential. Going down, converted from potential to kinetic
26Energy Conversion & Conservation MAIN IDEADETAILSWhat is the law of conservation of energy?Energy cannot be created or destroyed, but can be transformed to any other type of energyOR-When one form of energy is converted to another, no energy is destroyed in the process
27Energy Conversion & Conservation MAIN IDEADETAILSWhat is the relationship between energy and matter?Einstein: Energy can be created by destroying matterNuclear reactionsWhat is Conserving Energy?Not the same as conservation of energyMeans saving or not wasting energy
28Reality and Energy Conversions No energy conversion is 100% efficientSome energy is always lost to the environmentUsually as heatPower Generation through Energy Usage is a problem of efficiencyEfficiency = $$$$Heat is a form of pollutionGlobal warmingKills fish in lakes that are too warm
29Review Questions MAIN IDEA DETAILS What is an energy conversion? A change from one form of energy to another formState the law of conservation of energy in your own words:The total energy before a process is the same as the total after the process.
30Review Questions MAIN IDEA DETAILS Describe the energy conversions that occur when a ball is dropped and bounces back up. Why do you think the ball bounces a little lower each time?Falling: potential changes to kinetic.Bouncing back up: kinetic changes back to potentialBall does not bounce as high because some energy escapes as thermal (friction) or sound
31Energy Conversion & Conservation MAIN IDEADETAILSA roller coaster car with a mass of 500 Kg is at the top of the hill that is 30m high. Without friction, what would its kinetic energy be as it reached the bottom of the hill?Without friction, kinetic would equal gravitational potential:500kg x 9.8 m/s2 x 30 m = 147,000J
33Energy ConversionEnergy transformation, energy transfer, energy conversion or power transfer,any process of transforming one form of energy into another.Energy of fossil fuels, solar radiation, or nuclear fuels can be converted into other energy forms such as electrical, propulsive, or heating that are more useful to people.Often, machines are used to transform energy.The efficiency of a machine characterizes how well (how efficiently) it can produce a useful output (such as work for example) through such a conversion.
34Energy Conversion Coal Power Plants: For instance, a coal-fired power plant involves these power transfers:Potential energy in the coal converted to thermal energyThermal energy converted to kinetic energy in steamSteam energy converted to mechanical energy in the turbineMechanical energy of the turbine converted to electrical energy, which is the ultimate output
35Energy Conversions - Car Potential energy in the fuel converted to kinetic energy of expanding gas via combustionKinetic energy of expanding gas converted to linear piston movementLinear piston movement converted to rotary crankshaft movementRotary crankshaft movement passed into transmission assemblyRotary movement passed out of transmission assembly in second stepRotary movement passed through differentialRotary movement passed out of differential to drive wheelsRotary movement of drive wheels converted to linear motion of the vehicle
36Other Energy Conversions Thermophotovoltaics (Heat → Electricity)Geothermal power (Heat → Electricity)Heat engines, such as the internal combustion engine used in cars, or the steam engine (Heat → Mechanical energy)Ocean thermal power (Heat → Electricity)Hydroelectric dams (Gravitational potential energy → Electricity)Electric generator (Kinetic energy or Mechanical work → Electricity)Fuel cells (Chemical energy → Electricity)Lamp (Chemical energy → Heat and Light)Microphone (Sound → Electricity)Nuclear reactor (Nuclear energy → Electricity)Fossil fuel power plant (Chemical energy → Electricity)Solar cells (Light → Electricity), including downconversion and upconversionSolar thermal (Light → Heat)Wave power (Mechanical energy → Electricity)Windmills (Wind energy → Electricity or Mechanical energy)Piezoelectrics (Strain → Electricity)Acoustoelectrics (Sound → Electricity)
37Energy Conversion Efficiency Energy efficiencyCombustion engine10-50%Gas turbineup to 40%Gas & Steam Turbine Cooperationup to 60%Water Turbineup to 90% (practically achieved)Wind Turbineup to 59% (theoretical limit)Solar cellcurrent maximum 42.8% (50% short term goal)Firearm~30% (.300 Hawk ammunition)Fuel Cellup to 80%Water Electrolysis50%-70% (80%-94% theoretical maximum)Photosynthesisup to 6%Muscle14% - 27%Electric motors30-60% (small ones < 10W); (middle ones between W); % above 200WHousehold refrigeratorslow end systems ~ 20%; high end systems ~ 40-50%Incandescent bulbs5-10%Light Emitting Diodesup to 35% Fluorescent lamps28% Low pressure sodium lamps40.5% Metal halide lamps24% Electric shower90-95% ( Overall it would be more efficient to use a heat pump, requiring less electric energy)Electric heatersexactly 100% (all energy is always converted into heat anyway)
38Energy Conversion Efficiency Electric motors30-60% (small ones < 10W); (middle ones between W); % above 200WHousehold refrigeratorslow end systems ~ 20%; high end systems ~ 40-50%Incandescent bulbs5-10%Light Emitting Diodesup to 35% Fluorescent lamps28% Low pressure sodium lamps40.5% Metal halide lamps24% Electric shower90-95% ( Overall it would be more efficient to use a heat pump, requiring less electric energy)Electric heatersexactly 100% (all energy is always converted into heat anyway)
40Energy Conversion & Fossil Fuels MAIN IDEADETAILSHow are Fossil Fuels Formed?Stored energy from hundreds of millions of years ago, formed by geologic processesIncludes: coal, gas, petroleumContain energy that came from the sun
41Energy Conversion & Fossil Fuels MAIN IDEADETAILSHow do we use fossil fuels?Burned to release the potential chemical energyChemical changed to thermal (fire) to heat waterWater (steam) turns turbines (mechanical)Turbine turns a generator to make electricity
42Energy Conversion & Fossil Fuels MAIN IDEADETAILSHow is the chemical energy in fossil fuels related to the sun’s energy?Fossil fuels are stored energy from the sunHow is the energy of coal released?Combustion (burned) to release potential energy into thermal energy
43Energy Conversion & Fossil Fuels MAIN IDEADETAILSDescribe energy conversions involved in the formation of coal.Nuclear energy (sun) converted to electromagnetic (light)Light converted to chemical (Plants/animals)When exposed to high temperature and pressure over many years, it becomes coal.
44Energy Conversion & Fossil Fuels MAIN IDEADETAILSMake a general statement about the supply of fossil fuels, given what you know about how fossil fuels are formed:Fossil fuels are formed much more slowly than we are using them, so supply may become increasingly scarce.