EnergyEnergyChapter 15Chapter 15

What is energy?What is energy?•Defined as the ability to do Defined as the ability to do

work or the ability to cause work or the ability to cause change.change.

•Measured in joules.Measured in joules.•Can occur in many forms.Can occur in many forms.

Kinetic EnergyKinetic Energy• Energy of motionEnergy of motion• All moving objects All moving objects

possess kinetic possess kinetic energyenergy

• Can change from Can change from one type to one type to anotheranother

Factors which affect Factors which affect kinetic energy:kinetic energy:

•MASSMASS

•K.E = ½ mvK.E = ½ mv22

•VELOCITYVELOCITY

Potential Potential EnergyEnergy• Energy stored in an object due to Energy stored in an object due to

its position.its position.• Examples:Examples:

Gravitational potential Gravitational potential energyenergy

• Dependant on the weight of the Dependant on the weight of the object and its height above some object and its height above some reference point.reference point.

• Formula:Formula:

Elastic Potential EnergyElastic Potential Energy

• Potential energy due to to the Potential energy due to to the physical distortion of an object.physical distortion of an object.

• Depends on:Depends on:– Type of materialType of material– Amount of distortionAmount of distortion

Six main forms of energy:Six main forms of energy:

1. Mechanical energy1. Mechanical energy

• Energy associated with motion:Energy associated with motion:

2. Heat energy2. Heat energy

• Internal motion of particles of Internal motion of particles of matter that often causes a change matter that often causes a change in temperature.in temperature.

3. Chemical energy3. Chemical energy

• Energy released or stored when Energy released or stored when atoms are bonded together.atoms are bonded together.

• Bonds can be broken to release Bonds can be broken to release this energy.this energy.

4. Electromagnetic energy4. Electromagnetic energy

• A form of energy that travels A form of energy that travels through space in the form of through space in the form of waves.waves.

5. Nuclear energy5. Nuclear energy

• Found in the nucleus of the atomFound in the nucleus of the atom• Most Most concentrated form of energyconcentrated form of energy• Reason for the brightness and heat Reason for the brightness and heat

of the sunof the sun• Nuclear linkNuclear link

6. 6. Electrical energyElectrical energy

• Energy associated with electrical Energy associated with electrical charges or moving electrons.charges or moving electrons.

Energy conversionsEnergy conversions

• All forms of energy can change All forms of energy can change from one form to another.from one form to another.

• Examples:Examples:

Conservation of EnergyConservation of Energy

•Energy can be Energy can be neither created neither created nor destroyed.nor destroyed.

CalculationsCalculations

• When friction is absent or small When friction is absent or small enough to be ignored, total enough to be ignored, total mechanical energy = KE + PEmechanical energy = KE + PE

• Problems 1-3 page 458Problems 1-3 page 458

Theory of RelativityTheory of Relativity• Developed by Developed by

Albert Einstein in Albert Einstein in 1905.1905.

• Energy is directly Energy is directly related to mass.related to mass.

• E = mcE = mc22

Energy ResourcesEnergy Resources

• Nonrenewable:Nonrenewable:– Cannot be replaced after being used Cannot be replaced after being used

up. Examples:up. Examples:

Renewable resourcesRenewable resources

• Can be replaced in a relatively Can be replaced in a relatively short period of time. Examples:short period of time. Examples:

• HydroelectricHydroelectric• SolarSolar• WindWind• BiomassBiomass• ThermalThermal

Hydroelectric energyHydroelectric energy

• Energy obtained Energy obtained by damming a by damming a river and river and controlling the controlling the flow.flow.

• Potential energy Potential energy converted to converted to kinetic converted kinetic converted to electricto electric

Solar energySolar energy

• Using sunlight as an energy source Using sunlight as an energy source on earth.on earth.

• A huge amount of energy available, A huge amount of energy available, but problems include storage and but problems include storage and dependence on climate.dependence on climate.

Wind powerWind power

• Relatively Relatively unlimited unlimited amount of amount of energy energy available. available.

• Problem: What Problem: What if it is not if it is not windy?windy?

Geothermal energyGeothermal energy

• Using the heat beneath the Earth’s Using the heat beneath the Earth’s surface.surface.

Hydrogen fuel cells and Hydrogen fuel cells and biomassbiomass

• Hydrogen fuel cells: a way to Hydrogen fuel cells: a way to generate electricity by reacting generate electricity by reacting hydrogen with oxygen.hydrogen with oxygen.

• Biomass: using living organisms to Biomass: using living organisms to produce energy.produce energy.

assignmentassignment

• Page 469-470Page 469-470• 1-10, 12, 13, 14, 18, 21, 23, 25, 27, 1-10, 12, 13, 14, 18, 21, 23, 25, 27,

28, 29, 3228, 29, 32