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ENERGY
Above and beyond PE & KE
THE LAW:
• CONSERVATION OF ENERGY• ∑ E1 =∑E2• Energy cannot be created or
destroyed; it only changes form• Energy in = energy out• Heat, light and sound are common
forms of energy transfer
Many types of Energy
• Mechanical (PE & KE)• Gravitational • Kinetic • Chemical • Nuclear• Electromagnetic• Thermal
Mechanical Energy
• A object that is able to do work has mechanical energy
• Examples: Cars, trains, tractors, hammers, etc
Kinetic Energy (KE)
• The energy of motion• KE=1/2mv2
• Expressed as Joules (J)• Example: Book falling from shelf
Potential Energy (PE)
• Stored energy• “The energy of position in a force
field”• PE=mgh• Example: Book on a shelf• aka: gravitational energy
Thermal Energy
• When the amount of heat added to a system and something happens to the system, Thermal Energy is to blame
• Expressed as ΔQ• Example: Heat added to water
activates the water molecules, increasing the KE of the system
Chemical Energy
• When certain chemicals combine, energy is released
• Most important source of energy right now
• Example: Combustion of glucose (sugar) in our bodies• C6H12O6 +6O2 6CO2 + 6H2O +
690 kcal/mole
Electromagnetic Energy
• Waves transporting energy from one point to another
• Rapid variation of electric and magnetic field
• Examples: radio waves, microwaves, infrared radiation, visible light, ultraviolet, x-rays, gamma rays, etc
Electrical energy
• Energy due to the separation of charges
• Example: electricity!
Nuclear Energy
• aka mass energy• E= mc2
• Einstein first observed that anything with mass has energy
• Unstable isotopes can be fused or split thus liberating the energy within
• Examples: Fission & fusion
Nuclear Energy (cont’d)
• An incredibly small amount of mass has an incredibly large amount of energy
• Energy=mass x speed of light squared
• Speed of light = 3 x 108 m/s• 50 grams of mass has potential to
level an entire city
Elastic/Spring PE
• http://www.sciencejoywagon.com/physicszone/lessonch/05work/spring/speng.htm
PROBLEMS:
• http://127.0.0.1:26300/Principles_of_Physics/07_Work,%20Energy%20and%20Power/06/sp.html
• http://127.0.0.1:26300/Principles_of_Physics/07_Work,%20Energy%20and%20Power/07/sp.html
• http://127.0.0.1:26300/Principles_of_Physics/07_Work,%20Energy%20and%20Power/09/sp.html
From Chemical to Mechanical
• Dry Ice Bomb
Electromagnetic to Chemical
• Photosynthesis
Electromagnetic to Mechanical
• Motor
Electromagnetic to Thermal
• Heater
Chemical to Electromagnetic: Battery
Mechanical to Electromagnetic
• Generator• Windmill
Mechanical to Chemical
• Metabolizing food
Mechanical to Gravitational
• Projectile Motion
Mechanical to Thermal
• Friction
Gravitational to Electromagnetic
• Dam
Gravitational to Thermal
• Compression
Chemical to Thermal
• Combustion: refers to the rapid oxidation of fuel accompanied by the production of heat, or heat and light
Thermal to Mechanical
• Turbine
Thermal to Gravitational
• Temperature gradient: atmospheric and oceanic currents
Nuclear to Thermal
• Nuclear reactor