Chapter 4Chapter 4

EnergyEnergy

What is energy?What is energy?

Def:Def: ability to cause change ability to cause change Every change involves energyEvery change involves energy

Different FormsDifferent Forms

ElectricalElectrical Chemical – stored in food, involved in Chemical – stored in food, involved in

reactionsreactions Radiant – gives offRadiant – gives off Thermal – heatThermal – heat Same thing just different formsSame thing just different forms

Kinetic EnergyKinetic Energy

Def:Def: energy of a moving object energy of a moving object Depends on mass and speedDepends on mass and speed

Kinetic energy Kinetic energy (Joules) = (Joules) = 11 massmass (kg) x [ (kg) x [speedspeed (m/s)] (m/s)]22

22

KE = KE = 11 mv mv22

22 SI unit for energy is joule (J)SI unit for energy is joule (J)

Practice!Practice!

What is the kinetic energy of a .15 kg What is the kinetic energy of a .15 kg baseball moving at 40 m/s.baseball moving at 40 m/s.

A car moving at a speed of 20 m/s has a A car moving at a speed of 20 m/s has a kinetic energy of 300,000 J. What is the kinetic energy of 300,000 J. What is the car’s mass?car’s mass?

Potential EnergyPotential Energy

Even motionless objects have energyEven motionless objects have energy Stored in the object, has potential to Stored in the object, has potential to

changechange Def: Def: stored energystored energy

Elastic Potential EnergyElastic Potential Energy

Def:Def: stored energy by something stored energy by something that can stretch or compressthat can stretch or compress

Stretched rubber band – elastic Stretched rubber band – elastic potential energy potential energy kinetic energy kinetic energy

Chemical Potential EnergyChemical Potential Energy

Def:Def: energy stored in chemical bonds energy stored in chemical bonds Food, gasoline, etc.Food, gasoline, etc.

Gravitational Potential Gravitational Potential EnergyEnergy

Def:Def: stored energy by objects due to stored energy by objects due to position above earth (able to fall)position above earth (able to fall)

Practice!Practice!

Find the height of a .15 kg baseball Find the height of a .15 kg baseball that has a GPE of 73.5 J.that has a GPE of 73.5 J.

Find the GPE of a .3 kg coffee mug Find the GPE of a .3 kg coffee mug on a 1-m high counter.on a 1-m high counter.

What could you do to change GPE?What could you do to change GPE? Change height or massChange height or mass

Section 2Section 2

Conservation of EnergyConservation of Energy

Changing Forms of EnergyChanging Forms of Energy

Changing electrical energy – electricity – Changing electrical energy – electricity – light and heat energylight and heat energy

Energy is constantly changing formsEnergy is constantly changing forms

Transforming Chemical Transforming Chemical EnergyEnergy

Cars – MANY energy transformationsCars – MANY energy transformations Spark plug – gasoline – engine - wheelsSpark plug – gasoline – engine - wheels

Transforming Chemical Transforming Chemical EnergyEnergy

Green plants – take in sunlight and Green plants – take in sunlight and transform to chemical energy in transform to chemical energy in plantsplants

Mechanical EnergyMechanical Energy

Def:Def: total amount of potential and total amount of potential and kinetic energykinetic energy

Mechanical Energy = Potential + Mechanical Energy = Potential + KineticKinetic

Falling ObjectsFalling Objects

As potential As potential kinetic mechanical kinetic mechanical energy stays sameenergy stays same

Potential lost = Potential lost = kinetic gainedkinetic gained

Projectile MotionProjectile Motion

Mechanical energy remains constantMechanical energy remains constant Still see transformations of energyStill see transformations of energy

SwingingSwinging

Best part is falling Best part is falling from highest pointfrom highest point

High GPE = Low KEHigh GPE = Low KE

Describe Describe transition…transition…

Law of Conservation of Law of Conservation of EnergyEnergy

Def:Def: energy can not be created or energy can not be created or destroyeddestroyed

Energy just changes formEnergy just changes form All energy in the universe does not changeAll energy in the universe does not change Energy in = Energy outEnergy in = Energy out

Is energy always Is energy always conserved?conserved?

Swinging – you eventually will stop – Swinging – you eventually will stop – where does all the energy go?where does all the energy go?

Friction – air resistance = thermal energyFriction – air resistance = thermal energy

Human Body – Energy Human Body – Energy RelationsRelations

What forms of energy are in your What forms of energy are in your body?body?

Conservation of energy still trueConservation of energy still true Food, fat = potential energyFood, fat = potential energy Activity = kinetic energyActivity = kinetic energy Calorie 1C = 4,184 JCalorie 1C = 4,184 J

Chapter 6 Section 1Chapter 6 Section 1

Temperature and HeatTemperature and Heat

Matter in MotionMatter in Motion

Matter is made of tiny particles in constant Matter is made of tiny particles in constant motion motion have kinetic energy have kinetic energy

Faster = more kinetic energyFaster = more kinetic energy

TemperatureTemperature

Def:Def: measure of measure of averageaverage kinetic kinetic energy of particlesenergy of particles

High Temp. = High EnergyHigh Temp. = High Energy Low Temp. = Low EnergyLow Temp. = Low Energy Unit Unit Kelvin Kelvin

Thermal EnergyThermal Energy

Collisions between air and butter particles Collisions between air and butter particles increase energy of butter = higher increase energy of butter = higher temperaturetemperature

Def: Def: sum of kinetic and potential energy of sum of kinetic and potential energy of particles in objectparticles in object

Thermal EnergyThermal Energy

As temp increases = thermal energy As temp increases = thermal energy increasesincreases

If object has MORE MASS and at the same If object has MORE MASS and at the same temp. has HIGHER thermal energytemp. has HIGHER thermal energy

HeatHeat

Is your seat toasty?Is your seat toasty? Def:Def: thermal energy that flows from thermal energy that flows from

something at a higher temp to a something at a higher temp to a lower templower temp

Unit: JouleUnit: Joule

Beachin’ it up!Beachin’ it up!

How can there be extreme How can there be extreme differences in temperature from air, differences in temperature from air, sand and water?sand and water?

Sun rays are the same why different Sun rays are the same why different temp?temp?

Sand heats up 6 times faster than Sand heats up 6 times faster than waterwater

Specific HeatSpecific Heat

Specific Heat:Specific Heat: heat needed to raise 1kg heat needed to raise 1kg of material by 1of material by 1CC

Water as a CoolantWater as a Coolant

It’s high specific heat – absorb a lot of heat It’s high specific heat – absorb a lot of heat without changing temp muchwithout changing temp much

Strong bonds have to be broken before Strong bonds have to be broken before particles move really fastparticles move really fast