ENERGY Above and beyond PE & KE THE LAW: CONSERVATION OF ENERGY ∑ E1 =∑E2 Energy cannot be...

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