chapter 15: energy section 15.1 energy and its forms section 15.2 energy conversion and conservation...

Chapter 15: EnergyChapter 15: Energy

Section 15.1 Energy and Its FormsSection 15.1 Energy and Its FormsSection 15.2 Energy Conversion and Section 15.2 Energy Conversion and ConservationConservationSection 15.3 Energy ResourcesSection 15.3 Energy Resources

Section 15.1 Energy and Its FormsSection 15.1 Energy and Its Forms

Energy and WorkEnergy and Work

Work is done when a force moves an object Work is done when a force moves an object through a distance.through a distance.

Energy-the ability to do workEnergy-the ability to do work

Ie. Energy is transferred by a force moving an Ie. Energy is transferred by a force moving an object through a distance.object through a distance.

When work is done on an object, energy is When work is done on an object, energy is transferred to that object.transferred to that object.


Energy and WorkEnergy and Work

Key Concept: Work is a transfer of energy.Key Concept: Work is a transfer of energy.

Measured in joules (J)=1 newton-meterMeasured in joules (J)=1 newton-meter

Energy has different forms and comes from Energy has different forms and comes from different sources: sunlight, food, etc.different sources: sunlight, food, etc.


Kinetic EnergyKinetic Energy

Many forms of energy can be classified into two Many forms of energy can be classified into two general types: general types: kinetickinetic and and potentialpotential energy. energy.

Kinetic energy-the energy of motionKinetic energy-the energy of motion

Key Concept: The kinetic energy of any moving Key Concept: The kinetic energy of any moving object depends upon its mass and speed.object depends upon its mass and speed.


Kinetic EnergyKinetic Energy

Kinetic energy (KE)=1/2mvKinetic energy (KE)=1/2mv22

-m=mass (kg); v=speed (m/s)-m=mass (kg); v=speed (m/s)

**doubling the mass will double the kinetic **doubling the mass will double the kinetic energy; doubling the speed will quadruple it energy; doubling the speed will quadruple it

Section 15.1


Potential EnergyPotential Energy

def.-energy that is stored as a result of position def.-energy that is stored as a result of position or shapeor shape

Is converted to kinetic energyIs converted to kinetic energy

Two types: Two types: gravitational potential energy and gravitational potential energy and elastic potential energyelastic potential energy

Gravitational-potential energy that depends upon Gravitational-potential energy that depends upon an object’s heightan object’s height


Potential EnergyPotential EnergyKey Concept: An object’s gravitational potential Key Concept: An object’s gravitational potential energy depends on its mass, its height, and the energy depends on its mass, its height, and the acceleration due to gravity.acceleration due to gravity.Potential energy (PE)=mgh; Potential energy (PE)=mgh; m=massm=mass, , g=acceleration due to gravityg=acceleration due to gravity, h=, h=heightheightGravitational potential energy is directly related Gravitational potential energy is directly related to the mass of the object and its height .to the mass of the object and its height .


Potential EnergyPotential Energy

Elastic potential energy-the potential energy of Elastic potential energy-the potential energy of an object that is stretched or compressedan object that is stretched or compressed

““elasticelastic”-something springs back to its original ”-something springs back to its original shape after being stretched or compressed.shape after being stretched or compressed.

Ex. Rubber bands, springsEx. Rubber bands, springs


Forms of EnergyForms of Energy

Key Concept: The major forms of energy are Key Concept: The major forms of energy are mechanical energy, thermal energy, chemical mechanical energy, thermal energy, chemical energy, electrical energy, electromagnetic energy, electrical energy, electromagnetic energy, and nuclear energy.energy, and nuclear energy.

Each form can be converted into other forms of Each form can be converted into other forms of energy.energy.



mechanical energymechanical energy -the energy associated with -the energy associated with the motion and position of everyday objectsthe motion and position of everyday objects

-mechanical energy does not include thermal -mechanical energy does not include thermal energy, chemical energy, or other forms of energy, chemical energy, or other forms of energyenergy



thermal energythermal energy -the total potential and kinetic -the total potential and kinetic energy of all the microscopic particles in an energy of all the microscopic particles in an object.object.

As an object’s atoms move faster, its thermal As an object’s atoms move faster, its thermal energy increases and the object becomes energy increases and the object becomes warmer.warmer.

Objects that are hot enough can emit light.Objects that are hot enough can emit light.



chemical energychemical energy -the energy stored in chemical -the energy stored in chemical bonds.bonds.

When bonds are broken, the released energy When bonds are broken, the released energy can do work. can do work.

All chemical compounds store energy (including All chemical compounds store energy (including fuels).fuels).



electrical energyelectrical energy -the energy associated with -the energy associated with electrical chargeselectrical charges

They can exert forces that do workThey can exert forces that do work

electromagnetic energyelectromagnetic energy -a form of energy that -a form of energy that travels through space in the form of waves travels through space in the form of waves (visible light, x-rays)(visible light, x-rays)

Electromagnetic waves are often used for Electromagnetic waves are often used for communication b/c they travel long distances.communication b/c they travel long distances.

Section 15.2 Energy Conversion Section 15.2 Energy Conversion and Conservationand Conservation

Energy ConversionEnergy Conversion

Key Concept: Energy can be converted from Key Concept: Energy can be converted from one form to another.one form to another.

def.-the process of changing energy from one def.-the process of changing energy from one form to anotherform to another


Conservation of EnergyConservation of Energy

When energy changes from one form to another, When energy changes from one form to another, the total energy remains unchangedthe total energy remains unchanged even even though many energy conversions may occur.though many energy conversions may occur.

Key concept: The law of conservation of energy Key concept: The law of conservation of energy states that energy cannot be created or states that energy cannot be created or destroyed.destroyed.


Energy ConversionsEnergy Conversions**One of the most common energy conversions **One of the most common energy conversions is between potential energy and kinetic energy.is between potential energy and kinetic energy.Key Concept: The gravitational potential energy Key Concept: The gravitational potential energy of an object is converted to the kinetic energy of of an object is converted to the kinetic energy of motion as the object falls.motion as the object falls.Conversions b/t kinetic and potential energy can Conversions b/t kinetic and potential energy can happen in both directions.happen in both directions.


Energy Conversion in PendulumsEnergy Conversion in Pendulums(A weight swinging back and forth from a rope or (A weight swinging back and forth from a rope or string) Ex. clocksstring) Ex. clocksKinetic energy and potential energy undergo Kinetic energy and potential energy undergo constant conversion as a pendulum swings.constant conversion as a pendulum swings.At highest point, pendulum is briefly motionless At highest point, pendulum is briefly motionless while it changes direction.while it changes direction.The weight of the pendulum at that point has The weight of the pendulum at that point has zero kinetic energy and maximum potential zero kinetic energy and maximum potential energy.energy.


Energy Conversion in PendulumsEnergy Conversion in Pendulums

Pendulum swings down; potential energy is Pendulum swings down; potential energy is converted to kinetic energyconverted to kinetic energy

Pendulum has maximum kinetic energy and zero Pendulum has maximum kinetic energy and zero potential energy as it reaches the bottom of the potential energy as it reaches the bottom of the swing. (process repeats)swing. (process repeats)

Energy Conversion in the Pole Energy Conversion in the Pole VaultVault

Refer to Section 15.2 pg. 457Refer to Section 15.2 pg. 457


Energy Conversion CalculationsEnergy Conversion Calculations

When friction is small enough to be ignored, and When friction is small enough to be ignored, and no mechanical energy is added to a system, the no mechanical energy is added to a system, the system’s mechanical energy does not change.system’s mechanical energy does not change.

ME= KE + PEME= KE + PE

Conservation of Mechanical EnergyConservation of Mechanical Energy

(KE+ PE) (KE+ PE) beginning beginning = (KE + PE)= (KE + PE)end pg. 459end pg. 459

Section 15.2


Energy and MassEnergy and MassEinstein-developed his theory of relativity in 1905Einstein-developed his theory of relativity in 1905Key Concept: Einstein’s equation, E=mcKey Concept: Einstein’s equation, E=mc22, says , says that energy and mass are equivalent and can be that energy and mass are equivalent and can be converted into each other.converted into each other.E=energy; m=mass; c=speed of lightE=energy; m=mass; c=speed of lightEnergy is released as matter is destroyed, and Energy is released as matter is destroyed, and matter can be created from energy.matter can be created from energy.However, if was found that mass and energy However, if was found that mass and energy together are always conserved (together are always conserved (law of conservation law of conservation of energyof energy))

Section 15.3 Energy ResourcesSection 15.3 Energy Resources

Nonrenewable ResourcesNonrenewable Resources

**Energy resources can be classified as either **Energy resources can be classified as either renewable or nonrenewablerenewable or nonrenewable

Nonrenewable resources exist in limited Nonrenewable resources exist in limited quantities.quantities.

Once used, can’t be replaced except over the Once used, can’t be replaced except over the course of millions of years.course of millions of years.

Key Concept: Nonrenewable energy resources Key Concept: Nonrenewable energy resources include oil, natural gas, and uranium.include oil, natural gas, and uranium.


Nonrenewable Energy ResourcesNonrenewable Energy ResourcesIe. These resources are being used up much Ie. These resources are being used up much faster than they can be replaced.faster than they can be replaced.fossil fuelsfossil fuels -rich deposits of hydrocarbons -rich deposits of hydrocarbons formed underground from the remains of once-formed underground from the remains of once-living organisms (oil, natural gas, coal, and living organisms (oil, natural gas, coal, and uranium)uranium)Majority of the world’s energy use comes from Majority of the world’s energy use comes from fossil fuels.fossil fuels.


Renewable Energy ResourcesRenewable Energy Resources-def.-resources that can be replaced in a -def.-resources that can be replaced in a relatively short period of timerelatively short period of timeMost originate either directly or indirectly from Most originate either directly or indirectly from the sun. (generating electric power)the sun. (generating electric power)Key Concept: Renewable energy resources Key Concept: Renewable energy resources include hydroelectric, solar, geothermal, wind, include hydroelectric, solar, geothermal, wind, biomass, and, possibly in the future, nuclear biomass, and, possibly in the future, nuclear fusion.fusion.


Renewable Energy ResourcesRenewable Energy Resources

Hydroelectric EnergyHydroelectric Energy -energy obtained from -energy obtained from flowing waterflowing water

Flowing water is used to turn turbines that are Flowing water is used to turn turbines that are connected to electric generators.connected to electric generators.

Advantage: low cost, lack of pollutionAdvantage: low cost, lack of pollution

Disadvantage: dams cause environmental Disadvantage: dams cause environmental problems (fish population)problems (fish population)



Solar EnergySolar Energy -sunlight that is converted into -sunlight that is converted into unstable energyunstable energy

Used to warm houses, buildings, etc. (Heats Used to warm houses, buildings, etc. (Heats water)water)

Sunlight can be converted to electrical energy Sunlight can be converted to electrical energy (calculators)(calculators)

Adv. Nonpolluting; Dis. Cloudy areasAdv. Nonpolluting; Dis. Cloudy areas



Geothermal EnergyGeothermal Energy -thermal energy beneath -thermal energy beneath Earth’s surface.Earth’s surface.

Areas near volcanoes: this energy is used to Areas near volcanoes: this energy is used to generate electricity.generate electricity.

Water can be pumped into the ground and be Water can be pumped into the ground and be turned into steam.turned into steam.

Nonpolluting but not widely availableNonpolluting but not widely available


Other Renewable ResourcesOther Renewable Resources

Biomass energy-the chemical energy Biomass energy-the chemical energy stored in living things (can be converted stored in living things (can be converted directly into thermal energy)directly into thermal energy)

Ex. Using wood or peat to heat homes or Ex. Using wood or peat to heat homes or cook; corn stalks used for high-energy cook; corn stalks used for high-energy alcohol fuelalcohol fuel


Other Renewable ResourcesOther Renewable ResourcesHydrogen fuel cells-generate electricity by reacting Hydrogen fuel cells-generate electricity by reacting hydrogen with oxygen (can be used to convert energy hydrogen with oxygen (can be used to convert energy from renewable resources) Ex. Hydrogen fuelfrom renewable resources) Ex. Hydrogen fuelEnd product is water so: nonpolluting means for End product is water so: nonpolluting means for transporting energytransporting energyA form of hydrogen is also most likely raw material for A form of hydrogen is also most likely raw material for nuclear fusion (future).nuclear fusion (future).In In physicsphysics and and nuclear chemistrynuclear chemistry, , nuclear fusionnuclear fusion is the is the process by which multiple nuclei join together to form a process by which multiple nuclei join together to form a heavier nucleus. It is accompanied by the release or heavier nucleus. It is accompanied by the release or absorption of absorption of energyenergy..


Conserving Energy ResourcesConserving Energy ResourcesKey Concept: Energy resources can be Key Concept: Energy resources can be conserved by reducing energy needs and by conserved by reducing energy needs and by increasing the efficiency of energy use.increasing the efficiency of energy use.energy conservationenergy conservation -finding ways to use less -finding ways to use less energy or to use energy more efficientlyenergy or to use energy more efficientlyPeople should make energy-saving decisions to People should make energy-saving decisions to reduce the use of resources.reduce the use of resources.

chapter 15: energy section 15.1 energy and its forms section 15.2 energy conversion and conservation...

Documents

form of energy

energy conversion

energy resourcessection

transfer of energy

workelectromagnetic

nuclear energy

released energy

forms of energy section