5.2 – conservation of energy write what is in white
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5.2 – Conservation of Energy
Write what is in WHITE
Objectives
Describe how energy can be transformed from one form to another.
Explain how the mechanical energy of system is the sum of the potential and the kinetic energies.
Discuss the law of conservation of energy.
Changing Forms of Energy
Light bulb Light & HeatElectrical Radiant & Thermal
Changing Forms of Energy
Fuel Moving CarChemical Potential Thermal
Electric spark ignites fuelThermal Kinetic
Gases expand and move parts of engine
Less Obvious Changes
Green plants convert sunlight into energy stored in chemical bonds
Eating corn (chemical potential energy) becomes other forms of energy in your body
Kinetic & Potential Energy
Bikes, Roller coasters, Swings, Rubber Bands all involve Kinetic & Potential Energy
Mechanical energy is the total amount of potential and kinetic energy
in a system
Mechanical Energy
Energy due to the position and motion of an object or objects in a system
mechanical energy = potential energy + kinetic energy
Falling Objects
Object has gravitational potential energy due to Earth pulling it down
Object becomes loose and accelerates downward due to gravityLoses gravitational potential energyTransformed into kinetic energy as speed
increases
Projectile
Kinetic & Gravitational Potential Energy are converted between each other as ball rises and falls Kinetic Energy gets ball moving Kinetic Energy converted into GPE as ball rises GPE greatest at peak of path GPE converted back to Kinetic Energy as it moves
downward and increases speed
Swing
• Push gets you moving• KINETIC ENERGY
• Swing rises & loses speed• Kinetic changes into GRAVITATIONAL POTENTIAL
ENERGY
• Greatest at top of path
• Swing accelerates downward• GPE changes into KINETIC ENERGY
Law of Conservation of Energy
Energy cannot be created or destroyedEnergy simply changes from one form to
another, but total amount of energy never changes
Why don’t we always see conservation?
Friction & Air Resistance cause mechanical energy to be converted into thermal energyThat’s why chains get hot on a swing
Energy not created or destroyed, but changed into a new form
Nuclear Fusion
Sun’s energy Light & Heat on EarthSmall amount of mass is transformed
into tremendous amount of energyCombining of 2 or
more small nuclei into
one larger nucleus
In the reaction shown here, the nuclei of the hydrogen isotopes deuterium and tritium undergo fusion.
Nuclear Fission
Splitting of one large nucleus into 2 or more smaller nuclei
Power Plants create electrical energy using fission
Human Body
Chemical Potential Energy maintains body temperatureExcess given off as heat to environment
CPE fuels processes such as heart beat and food digestionEnergy is converted into heat and
movement
Human Body
Obeys Law of Conservation of Energy
To maintain a healthy weight you must have a balance between energy consumed and energy usedExcess energy can be stored
as fat
Food Energy
Chemical Potential Energy1 food Calorie (C) = 4,184 Joules
1 gram fat = 9 Calories1 gram of carbohydrates & proteins = 4 C
In-Class Assignment/Homework
5.2 WKT
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