ENERGY:What do we remember?

ENERGYWhere is energy found and when?

Energy is around you all the timeWhat is energy?

Ability to do workWhen work is done, what happens to energy?

Energy is given offWhat is the SI unit for energy?

Joules (J)Energy has the same SI unit as what?

Work

What are the two states of energy?

What can you tell me about KINETIC ENERGY?(KE)

• Greek = kinetikos = “moving”• Energy of motion/movement• Depends on mass and speed• KE = mv2

2 • ↑ speed = ↑ KE• ↑ mass = ↑ KE• Speed has greater effect than mass

What can you tell me about POTENTIAL ENERGY (PE)

• Energy of position/shape• Stored energy• Gravitational Potential Energy (GPE)– (GPE) = weight x height– N x m = J

MECHANICAL ENERGY (ME)

• Objects total energy of motion and position• ME = PE + KE• PE ↑ = KE ↓• PE ↓ = KE ↑• ME remains constant

8

Pendulum

9

Car on an incline

Energy can take different forms…

THERMAL ENERGY

• KE• Total energy of particles (atoms and

molecules) that make up object • ↑ movement = ↑ KE = ↑ temp. = ↑ thermal

energy• Particles far apart have more energy than

particles close together.

Energy vs. Thermal energy

Least Mostenergy energy

most thermal energy

Particle movement

Amount of particles

CHEMICAL ENERGY

• PE• Compound energy that changes arrangement

of atoms• Stored in bonds between atoms• Chemical rxn takes place

ELECTRICAL ENERGY

• KE• Moving electrons back and forth through wire

or current• Produced at power plants

SOUND ENERGY

• PE and KE• Energy of vibrations• Transmits energy to air• Carried through solids, liquids, and gases• Travels in waves

LIGHT/RADIANT ENERGY

• Not all light can be seen• Vibrations of electrically charged particles• Travels through waves and empty space

NUCLEAR ENERGY

• Produced from change of nucleus• Two types– Fission: splitting nucleus (electrical energy)– Fusion: joining nuclei (sun)

• Uranium:– stores a lot of PE– energy used from nuclei being split– generated at nuclear power plants

VENN DIAGRAM OF FORMS OF ENERGY

POTENTIALENERGY

KINETICENERGY

CHEMICAL

NUCLEAR

THERMAL

ELECTRICAL

LIGHT/RADIANTSOUND

ENERGY CONVERSIONS

• Transfer/change/conversion of energy from one form to another

• Can be transferred converted to more than one form

Energy Conversions

“Breakfast is the most important meal of the day.”

Eating Being active Body temperature

ChemicalEnergy

KineticEnergy

ThermalEnergy

Energy Conversions

electrical

light andsound

chemical electrical

electricalkineticandsound

electricallightandthermal

electricalkinetic,thermal,and sound

Energy Conversions

Energy Conversions

Energy Conversions

Explain the energy conversions below.

ENERGY AND MACHINES

• Machines make work easier by changing– Size– Direction– or both of the force required to do the work

• Machines transfer energy and convert energy

Why are energy conversions important?

• It is useful for every day life.– Ex. Wind used to cook a meal

• Efficiency– Ex. Energy efficient light bulbs and appliances

WHERE DOES THE ENERGY GO?• Energy is never lost but converted to other forms of

energy• Hills and friction help to tell what happens to energy• Energy is used to overcome friction• Some of the energy is always converted to thermal

energy

Law of Conservation of Energy

• Energy can neither be created or destroyed• Closed system- well-defined group of

objects that transfer energy between each other.• Total amount of energy always the

same• Ex. Roller coaster, light bulb

Perpetual motion machine

• Runs forever without additional energy• Energy in = Energy out

• Will never happen because some energy is turned into thermal energy.

REFERENCES

• http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/energy/ce.html

http://www.physicsclassroom.com/mmedia/energy/se.html