Energy and It’s FormsEnergy and It’s Forms

EnergyEnergy

Chapter 15 Section 1Chapter 15 Section 1

Physical SciencePhysical Science

Energy and WorkEnergy and Work

Energy is known by the changes it causes Energy is known by the changes it causes ex: sound or motion (hear an avalanche ex: sound or motion (hear an avalanche and see the snow)and see the snow)

Work is a force acting through a distanceWork is a force acting through a distance Energy is the ability to do work; energy is Energy is the ability to do work; energy is

transferred by a force moving an object transferred by a force moving an object through a distancethrough a distance

Energy and WorkEnergy and Work When work is done on an object, energy is When work is done on an object, energy is

transferred to that objecttransferred to that object Work is a transfer of energyWork is a transfer of energy Both work and energy are measured in joulesBoth work and energy are measured in joules

TASK: carry backpack up the stairsTASK: carry backpack up the stairsDo work on the backpack by lifting in against the Do work on the backpack by lifting in against the

force of gravity. You get the energy from your force of gravity. You get the energy from your muscles, your muscles get the energy from food. muscles, your muscles get the energy from food. The food gets its energy from plants (or animals The food gets its energy from plants (or animals that eat plants) that get their energy from the that eat plants) that get their energy from the sunsun

Kinetic EnergyKinetic Energy

There are MANY forms of energy, but it There are MANY forms of energy, but it can be classified into 2 types : kinetic and can be classified into 2 types : kinetic and potentialpotential

Kinetic EnergyKinetic Energy is the energy of motion is the energy of motion

Greek “kinetos” means movingGreek “kinetos” means moving

Kinetic Energy (KE) = ½ mvKinetic Energy (KE) = ½ mv2 2

units are joulesunits are joules

kilograms

m/s

Potential EnergyPotential Energy Potential energyPotential energy is energy that is stored as a result to is energy that is stored as a result to

position or shape. It is energy with the potential to do position or shape. It is energy with the potential to do workwork

Ex: when playing a guitar, you pull the strings back in order Ex: when playing a guitar, you pull the strings back in order to create music. The energy is stored in the stretched to create music. The energy is stored in the stretched string and it gains potential energy. When you let the string and it gains potential energy. When you let the string go, the potential energy (stored energy) is string go, the potential energy (stored energy) is converted into kinetic energy (energy of motion) converted into kinetic energy (energy of motion)

EX: you can also store energy when you lift a book and EX: you can also store energy when you lift a book and hold it in the air. Let go of the book and the potential hold it in the air. Let go of the book and the potential energy (stored energy) is turned into kinetic energy energy (stored energy) is turned into kinetic energy (energy of motion) as the book falls to the floor (energy of motion) as the book falls to the floor

Potential EnergyPotential Energy Two types of potential energy: gravitational and elasticTwo types of potential energy: gravitational and elastic Gravitational Potential Energy is potential energy that Gravitational Potential Energy is potential energy that

depends on an objects heightdepends on an objects heightIncreases when an object is raised to a higher levelIncreases when an object is raised to a higher levelEx: person sitting in a dunk tank has GPE. When the seat Ex: person sitting in a dunk tank has GPE. When the seat

is let go GPE is converted into KE, work is done as the is let go GPE is converted into KE, work is done as the person falls in the waterperson falls in the water

Depends on mass, height and gravityDepends on mass, height and gravity

Gravitational Potential Energy (GPE) = mghGravitational Potential Energy (GPE) = mgh units are joulesunits are joules

Mass kg Height m

Accel. Gravity 9.8 m/s2

Elastic Potential EnergyElastic Potential Energy

The potential energy of an object that is The potential energy of an object that is stretched or compressed is elastic potential stretched or compressed is elastic potential energyenergy

Something is considered elastic if it springs back Something is considered elastic if it springs back to original shape after being stretched or to original shape after being stretched or compressedcompressed

Ex: stretch a rubber band, you do work on the Ex: stretch a rubber band, you do work on the rubber band and the energy is stored as elastic rubber band and the energy is stored as elastic potential energypotential energy

Example Energy ProblemsExample Energy Problems

A .1 kg bird is flying at a constant speed of A .1 kg bird is flying at a constant speed of 8.0 m/s. What is the birds kinetic energy?8.0 m/s. What is the birds kinetic energy? KE = ½ (.1 kg) (8 m/s)KE = ½ (.1 kg) (8 m/s)22

KE = 3.2 JKE = 3.2 J A diver at the top of a 10 m high diving A diver at the top of a 10 m high diving

platform has a mass of 50 kg. Calculate platform has a mass of 50 kg. Calculate the potential energy of the diver.the potential energy of the diver.

PE = (50 kg) (9.8 m/sPE = (50 kg) (9.8 m/s22) (10 m)) (10 m) PE = 4900 JPE = 4900 J

Forms of Energy: MechanicalForms of Energy: Mechanical Mechanical EnergyMechanical Energy is the energy associated is the energy associated

with the motion and position of everyday objectswith the motion and position of everyday objectsApplies to more than just machinesApplies to more than just machines

The sum of an objects potential and kinetic The sum of an objects potential and kinetic energyenergy

Created from chemical energyCreated from chemical energyEX: speeding train (kinetic), sprinting athlete EX: speeding train (kinetic), sprinting athlete

(kinetic), bouncing ball (kinetic and potential), (kinetic), bouncing ball (kinetic and potential), pulling back a arrow (potential), holding a barbell pulling back a arrow (potential), holding a barbell above your head (potential) above your head (potential)

Forms of Energy: ThermalForms of Energy: Thermal Everything is made of matter and matter is made of Everything is made of matter and matter is made of

particles.particles. The particles are always randomly moving and thus have The particles are always randomly moving and thus have

kinetic energykinetic energy Thermal EnergyThermal Energy is the total kinetic energy of the is the total kinetic energy of the

microscopic particles in an object. Related to temp and microscopic particles in an object. Related to temp and heatheat

The faster an objects atoms move, the more its thermal The faster an objects atoms move, the more its thermal energy increases and the object becomes warmer. energy increases and the object becomes warmer. When hot, the object may emit lightWhen hot, the object may emit light

EX: boiling water; thermal energy or heat is applied to the EX: boiling water; thermal energy or heat is applied to the bottom of the pot. The energy is transferred to the water. bottom of the pot. The energy is transferred to the water. The particles in the water begin moving faster and the The particles in the water begin moving faster and the water will turn to steamwater will turn to steam

Forms of Energy: ChemicalForms of Energy: Chemical Chemical EnergyChemical Energy is the energy stored in chemical is the energy stored in chemical

bondsbonds When the bonds are broken, the released energy can do When the bonds are broken, the released energy can do

workwork All chemical compounds store energy, including coal and All chemical compounds store energy, including coal and

gasolinegasoline

EX: cars use the chemical energy stored in gas to move. EX: cars use the chemical energy stored in gas to move. Some of the chemical energy is converted into Some of the chemical energy is converted into mechanical energy to move the carmechanical energy to move the car

EX: a fire is fueled from the chemical energy stored in EX: a fire is fueled from the chemical energy stored in wood. Some of the chemical energy is converted to wood. Some of the chemical energy is converted to thermal energy and produces heat and lightthermal energy and produces heat and light

Forms of Energy: ElectricalForms of Energy: Electrical

Electrical EnergyElectrical Energy is the energy is the energy associated with electrical charges that associated with electrical charges that exert energy to do workexert energy to do work

Many devices use electricity, or electrical Many devices use electricity, or electrical energyenergy

EX: batteries convert chemical energy into EX: batteries convert chemical energy into electrical energy to operate flashlights, CD electrical energy to operate flashlights, CD players, cell phones and radiosplayers, cell phones and radios

Forms of Energy: ElectromagneticForms of Energy: Electromagnetic

The sun radiates electromagnetic energy into space and The sun radiates electromagnetic energy into space and it the source (directly or indirectly) of most of the worlds it the source (directly or indirectly) of most of the worlds energy supplyenergy supply

Electromagnetic EnergyElectromagnetic Energy is a form of energy that travels is a form of energy that travels through space in the form of wavesthrough space in the form of waves

Waves can travel long distances through air and spaceWaves can travel long distances through air and space

EX: visible light and x-raysEX: visible light and x-raysEX: plants use the electromagnetic solar energy and EX: plants use the electromagnetic solar energy and

convert it to chemical energy through a process called convert it to chemical energy through a process called photosynthesisphotosynthesis

Forms of Energy: NuclearForms of Energy: Nuclear The nucleus of an atom is held together by strong and The nucleus of an atom is held together by strong and

weak nuclear force, which can store a lot of potential weak nuclear force, which can store a lot of potential energyenergy

The energy stored in the atomic nucleus is called nuclear The energy stored in the atomic nucleus is called nuclear energyenergy

EX: A nuclear power plant uses nuclear fission reactions to EX: A nuclear power plant uses nuclear fission reactions to generate electricity. Nuclear fission releases energy generate electricity. Nuclear fission releases energy from splitting nuclei apartfrom splitting nuclei apart

EX: Nuclear Fusion releases energy from combining less EX: Nuclear Fusion releases energy from combining less massive nuclei to form more massive nuclei. The heat massive nuclei to form more massive nuclei. The heat and light of the sun is produced from the fusion of and light of the sun is produced from the fusion of hydrogen nuclei into helium nucleihydrogen nuclei into helium nuclei

Energy Can Change FormsEnergy Can Change Forms

Energy forms can be converted from one Energy forms can be converted from one form to anotherform to another

Light bulb uses electrical energy Light bulb uses electrical energy (produces light), some of that energy is (produces light), some of that energy is converted to thermal energy (produces converted to thermal energy (produces heat)heat)

Energy can be transformed; IT CANNOT Energy can be transformed; IT CANNOT BE CREATED OR DESTROYED!!!BE CREATED OR DESTROYED!!!