Embed Size (px)
Citation preview
Energy:Energy:Forms andForms andChangesChanges
Nature of Energy
Energy is all around you! You can hear energy as sound. You can see energy as light. And you can feel it as wind.
Nature of Energy
You use energywhen you: hit a softball. lift your book
bag. compress a
spring.
Nature of Energy
Living organisms needenergy for growth and
movement.
Nature of Energy
Energy is involvedwhen: a bird flies. a bomb explodes. rain falls from the
sky. electricity flows in
a wire.
Nature of Energy
What is energy that it can beinvolved in so many differentactivities? Energy can be defined as the
ability to do work. If an object or organism does
work (exerts a force over adistance to move an object) theobject or organism uses energy.
Nature of Energy
Because of the directconnection between energy andwork, energy is measured inthe same unit as work: joules(J).
In addition to using energy todo work, objects gain energybecause work is being done onthem.
Forms of Energy
The five main formsof energy are:
Heat Chemical Electromagnetic Nuclear Mechanical
Heat Energy
The internal motion of the atoms iscalled heat energy, because movingparticles produce heat.
Heat energy can be produced byfriction.
Heat energy causes changes intemperature and phase of any formof matter.
Chemical Energy
Chemical Energy is required tobond atoms together.
And when bonds are broken,energy is released.
Chemical Energy
Fuel and foodare forms ofstoredchemicalenergy.
Electromagnetic Energy
Power lines carry electromagneticenergy into your home in the form ofelectricity.
Electromagnetic Energy
Light is a form ofelectromagnetic energy.
Each color of light (Roy GBv) represents a differentamount ofelectromagnetic energy.
Electromagnetic Energy isalso carried by X-rays,radio waves, and laserlight.
Nuclear Energy
The nucleusof an atom isthe source ofnuclearenergy.
Nuclear Energy
When the nucleus splits (fission),nuclear energy is released in theform of heat energy and lightenergy.
Nuclear energy is also releasedwhen nuclei collide at high speedsand join (fuse).
Nuclear Energy
The sun’s energyis produced froma nuclear fusionreaction in whichhydrogen nucleifuse to formhelium nuclei.
Nuclear Energy
Nuclearenergy is themostconcentratedform ofenergy.
Most of us live within 10 miles of the SurryNuclear Power Plant which converts nuclearenergy into electromagnetic energy.
Mechanical Energy
When work is done to anobject, it acquires energy.The energy it acquires isknown as mechanical energy.
Mechanical Energy
When youkick afootball, yougivemechancalenergy to thefootball tomake it move.
Mechanical Energy
When you throw aballing ball, yougive it energy.When thatbowling ball hitsthe pins, some ofthe energy istransferred to thepins (transfer ofmomentum).
Energy Conversion
Energy can be changed from oneform to another. Changes in theform of energy are called energyconversions.
Energy conversions
All forms of energy can beconverted into other forms. The sun’s energy through solar cells
can be converted directly intoelectricity.
Green plants convert the sun’s energy(electromagnetic) into starches andsugars (chemical energy).
Other energy conversions
In an electric motor, electromagneticenergy is converted to mechanicalenergy.
In a battery, chemical energy isconverted into electromagnetic energy.
The mechanical energy of a waterfall isconverted to electrical energy in agenerator.
Energy Conversions
In an automobileengine, fuel isburned to convertchemical energyinto heat energy.The heat energy isthen changed intomechanicalenergy.
Chemical Heat Mechanical
States of Energy
The most common energyconversion is the conversionbetween potential and kineticenergy.
All forms of energy can be in eitherof two states: Potential Kinetic
States of Energy:Kinetic and Potential Energy
Kinetic Energy is theenergy of motion.
Potential Energy isstored energy.
Kinetic Energy
The energy of motion is calledkinetic energy.
The faster an object moves, themore kinetic energy it has.
The greater the mass of a movingobject, the more kinetic energy ithas.
Kinetic energy depends on bothmass and velocity.
Kinetic Energy
K.E. = mass x velocity 2
What has a greater affect of kineticenergy, mass or velocity? Why?
Potential Energy
Potential Energy is stored energy. Stored chemically in fuel, the nucleus
of atom, and in foods. Or stored because of the work done on
it: Stretching a rubber band. Winding a watch. Pulling back on a bow’s arrow. Lifting a brick high in the air.
Gravitational Potential Energy
Potential energythat is dependenton height is calledgravitationalpotential energy.
Potential Energy
Energy that is stored due to beingstretched or compressed is calledelastic potential energy.
Gravitational Potential Energy
A waterfall, a suspension bridge, and afalling snowflake all have gravitationalpotential energy.
Gravitational Potential Energy
If you stand on a3-meter divingboard, you have 3times the G.P.E,than you had on a1-meter divingboard.
Gravitational Potential Energy
“The bigger they are the harderthey fall” is not just a saying. It’strue. Objects with more mass havegreater G.P.E.
The formula to find G.P.E. isG.P.E. = Weight X Height.
Kinetic-Potential Energy Conversion
Roller coasters work because of the energy that isbuilt into the system. Initially, the cars are pulledmechanically up the tallest hill, giving them a greatdeal of potential energy. From that point, theconversion between potential and kinetic energypowers the cars throughout the entire ride.
Kinetic vs. Potential Energy
At the point of maximum potential energy, the car hasminimum kinetic energy.
Kinetic-Potential Energy Conversions
As a basketballplayer throws theball into the air,various energyconversions takeplace.
Ball slows down Ball speeds up
The Law of Conservation of Energy
Energy can be neither created nordestroyed by ordinary means. It can only be converted from one form
to another. If energy seems to disappear, then
scientists look for it – leading to manyimportant discoveries.
Law of Conservation of Energy
In 1905, Albert Einstein said thatmass and energy can be convertedinto each other.
He showed that if matter isdestroyed, energy is created, and ifenergy is destroyed mass iscreated. 2
E = MC
Vocabulary Wordsenergymechanical energyheat energychemical energyelectromagnetic energynuclear energykinetic energypotential energygravitational potential energyenergy conversionLaw of Conservation of Energy
