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Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in...

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Page 1: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Energy

Page 2: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

• Energy is the ability to do work–Work is a transfer of energy

• Energy is measured in joules (J)– 1 joule = work done to move an object 1

meter by 1 N

Page 3: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Kinetic NRG• Energy of a moving object• KE = 1/2mv2

• m = mass and v = velocity• Square velocity first• Double the mass, double

the KE• Double the velocity,

quadruple the KE

Page 4: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Potential NRG• Stored energy• Gravitational potential

energyPE = mghm = mass g = gravity h = height

• Greater the height, more PE

• Greater the mass, more PE

Page 5: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

• Elastic potential energy–When an object is stretched or compressed– The more stretched, the more potential

energy– The more compressed, the more potential

energy

Page 6: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

• Can there be kinetic energy and potential energy at the same time?– Yes!– Mechanical energy = KE + PE

motion position

• Do you think energy can be created or destroyed?– No!– So the total amount of energy at the beginning

will be the same at the end

Page 7: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.
Page 8: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Forms of NRG

• Mechanical• Thermal• Chemical• Electrical• Electromagnetic• Nuclear

Page 9: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Mechanical• Energy associated with motion and

position• Sum of potential and kinetic energy

Page 10: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Chemical• Energy stored in chemical bonds• Bonds are broken, energy is released• Examples– Chemical compounds, such as fuels– Food–Muscles

Page 11: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Electrical

• Associated with electric charges• Batteries convert chemical energy

into electrical energy

Page 12: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Electromagnetic• Form of energy that travels through space in

the form of waves• Ex: light, X-rays, radio waves• Often used for communication because they

travel long distances

Page 13: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Nuclear• Energy stored in atomic nuclei• Nucleus held by strong and weak forces

(Large amount of PE)• Fission (split nuclei)• Fusion (combine nuclei)

Page 14: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Thermal• Potential and kinetic energy of atomic

particles• When atoms move faster, thermal energy

increases and object becomes warmer

Page 15: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Energy Conversions• Energy can be converted from one form

to another• What type of energy conversion takes

place when lighting a match?Chemical: rxns in muscles allow you to move the match

Kinetic: match is moving

Thermal: heat produced by friction

Chemical: rxn on match’s tip triggered by thermal energy

Thermal: heat produced

Electromagnetic: light produced

Page 16: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Conservation of Energy• Energy cannot be created or destroyed, it can

only be transferred• Ex: Bike slowing– Kinetic NRG becomes thermal NRG– Friction between the bike and the ground/air– Lose kinetic NRG, gain thermal NRG, total

NRG is the same• Ex: Pole vault– KE Elastic PE Gravitational PE KE

• (KE + PE)beginning = (KE + PE)end

Page 17: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Heat • TOTAL amount of kinetic energy of

particles• Transfer of thermal energy because of

temperature differences• Moves from hot to cold objects

Page 18: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Temperature• AVERAGE amount of

kinetic energy of particles

• Measure of how hot or cold something is

• Use a thermometer• Celsius and Kelvin

scales• Absolute zero = 0 K

• Object heats up, particles move faster

Page 19: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Thermal Contraction and Expansion

• If temp decreases, particles move slower and closer together, so object contracts

• If temp increases, particles move faster and farther away, so object expands

Page 20: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Thermal NRG Absorption• Depends on color, texture, and

exposed surface area

Absorb more than emit = temp increase

Emit more than absorb = temp decrease

Absorb and emit the same amount = thermal equilibrium

Page 21: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Specific Heat• Amount of heat needed to raise the

temperature of one gram of an object one degree Celsius

• Lower specific heat = temp rises more when given a certain amount of energy

• Q = m x c x change in T or Q = mc∆T• Q = heat gained or lost (J)• m = mass (g)• c = specific heat (SI unit: J/g • ˚C)• T = temperature (˚C)

Page 22: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Conduction• Transfer of thermal energy with no

overall transfer of matter• Objects must be touching to transfer

heat

Page 23: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

• Conductors – conduct thermal energy well–Most metals are good conductors

because electrons move easily

• Insulators – conduct thermal energy poorly

Page 24: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Convection• Transfer of thermal energy when

particles of a fluid move from place to place

• Convection current–Warm air rises– Cool air sinks

Page 25: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

Radiation• Transfer of energy by waves moving

through space• All objects radiate energy– Heat lamps– Sun

Page 26: Energy. Energy is the ability to do work – Work is a transfer of energy Energy is measured in joules (J) – 1 joule = work done to move an object 1 meter.

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