Unit 3Unit 3

Energy Energy

and and

WorkWork

EnergyEnergy

Energy is the ability to do workEnergy is the ability to do work

Energy is all around usEnergy is all around us

There are two basic kinds of energyThere are two basic kinds of energy

The two basic kinds of energy:The two basic kinds of energy:

Potential energyPotential energy

Kinetic energyKinetic energy

Potential EnergyPotential Energy

Potential energy is stored energyPotential energy is stored energy

There are two types of potential energyThere are two types of potential energy– Chemical potential energyChemical potential energy– Gravitational potential energyGravitational potential energy

Chemical Potential EnergyChemical Potential Energy

Chemical potential energy is energy that Chemical potential energy is energy that can be released as the result of a can be released as the result of a chemical reactionchemical reaction– Ex. Matches, food, gasolineEx. Matches, food, gasoline

Gravitational Potential EnergyGravitational Potential Energy

Gravitational potential energy is also Gravitational potential energy is also known as known as energy of positionenergy of position

Gravitational potential energy depends on Gravitational potential energy depends on an object’s an object’s weight and heightweight and height

Kinetic EnergyKinetic Energy

Kinetic energy is energy of motionKinetic energy is energy of motion

A moving object has kinetic energyA moving object has kinetic energy

Kinetic EnergyKinetic Energy

Kinetic energy depends on Kinetic energy depends on speed and speed and massmass– The faster an object is moving, the greater its The faster an object is moving, the greater its

kinetic energykinetic energy– The greater an object’s mass, the greater its The greater an object’s mass, the greater its

kinetic energykinetic energy

Forms of EnergyForms of Energy

There are five main forms of energyThere are five main forms of energy– Mechanical EnergyMechanical Energy– Electromagnetic EnergyElectromagnetic Energy– Heat EnergyHeat Energy– Chemical EnergyChemical Energy– Nuclear EnergyNuclear Energy

Mechanical EnergyMechanical Energy

The energy in moving thingsThe energy in moving things

– Includes soundIncludes sound

Electromagnetic EnergyElectromagnetic Energy

Energy in moving electronsEnergy in moving electrons

– Includes electricity and lightIncludes electricity and light

Heat EnergyHeat Energy

Energy in moving particles of matterEnergy in moving particles of matter

– The faster a particle moves, the more heat The faster a particle moves, the more heat energy it hasenergy it has

– All things contain some heat energyAll things contain some heat energy

Chemical EnergyChemical Energy

Energy that holds particles of matter Energy that holds particles of matter togethertogether

– Energy in fuel such as wood or coal is Energy in fuel such as wood or coal is chemical energychemical energy

Nuclear EnergyNuclear Energy

Energy stored in the nuclei of atomsEnergy stored in the nuclei of atoms

– Heat and light from the sun are produced from Heat and light from the sun are produced from nuclear energynuclear energy

EnergyEnergy

Energy can change from one form to Energy can change from one form to anotheranother

– When energy changes form, some of the When energy changes form, some of the energy is always changed into heat energyenergy is always changed into heat energy

– Most of this heat energy is lost as wasteMost of this heat energy is lost as waste

Thermal PollutionThermal Pollution

Thermal pollution is damage that occurs Thermal pollution is damage that occurs when waste heat enters the environmentwhen waste heat enters the environment

Conservation of EnergyConservation of Energy

Law of Conservation of EnergyLaw of Conservation of Energy

– Energy cannot be made or destroyed, but can Energy cannot be made or destroyed, but can only change in formonly change in form

Scientific TheoryScientific Theory

A scientific theory is an idea supported by A scientific theory is an idea supported by evidence over a period of timeevidence over a period of time

The Law of Conservation of Energy is a The Law of Conservation of Energy is a scientific theoryscientific theory

Matter and EnergyMatter and Energy

Matter can be changed into energyMatter can be changed into energy

Energy can be changed into matterEnergy can be changed into matter

– The total amount of matter and energy in the The total amount of matter and energy in the universe does not changeuniverse does not change

– This is explained by the equation:This is explained by the equation:

E=mcE=mc22

E=mcE=mc22

E – energyE – energy

m – matter or massm – matter or mass

c – speed of lightc – speed of light

WorkWork

Work equals force times distanceWork equals force times distance

WorkWork

Work is done when a force moves an Work is done when a force moves an object a certain distanceobject a certain distance

– If an object is not moved, no work is doneIf an object is not moved, no work is done

WorkWork

Energy is the ability to do workEnergy is the ability to do work

– However, energy can be used without doing However, energy can be used without doing workwork

WorkWork

For work to be done, the direction of the For work to be done, the direction of the applied force must be the same as the applied force must be the same as the direction of the motiondirection of the motion

Measuring WorkMeasuring Work

To measure work, you must know:To measure work, you must know:

– The force in NewtonsThe force in Newtons

– The distance in metersThe distance in meters

– Work can be measured in Newton-metersWork can be measured in Newton-meters(N-m)(N-m)

JoulesJoules

The metric unit of work is the Joule (J)The metric unit of work is the Joule (J)

– 1 J (Joule) = 1 N-m (Newton-meter)1 J (Joule) = 1 N-m (Newton-meter)

Measuring WorkMeasuring Work

When measuring work, you must measure When measuring work, you must measure the force applied in the direction of motionthe force applied in the direction of motion

PowerPower

Power is the amount of work done per unit Power is the amount of work done per unit of timeof time

Power is the rate at which work is donePower is the rate at which work is done

Power = work / timePower = work / time

Power = (force X distance) / timePower = (force X distance) / time

PowerPower

The metric unit of power is the Watt (W)The metric unit of power is the Watt (W)

– 1 Watt (W) = 1 Joule per second (J/sec)1 Watt (W) = 1 Joule per second (J/sec)1 W = 1 N-m/sec1 W = 1 N-m/sec

1 W = 1 J/sec1 W = 1 J/sec

PowerPower

Large amounts of power are measured in Large amounts of power are measured in kilowatts (kW)kilowatts (kW)

– 1 kW = 1000 W1 kW = 1000 W