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Energy Forms

Energy Forms. Mechanical Energy. Associated with the position and motion of an object. A combination of an object’s PE and KE (total energy of the object at any one time) An object with ME can do work on another object. ME = the ability to do work

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Energy Forms

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  1. Energy Forms

  2. Mechanical Energy • Associated with the position and motion of an object. • A combination of an object’s PE and KE (total energy of the object at any one time) • An object with ME can do work on another object. • ME = the ability to do work • The more ME, the more work an object can do

  3. Calculating ME • ME = PE + KE • Sometimes an object’s ME is just its potential energy and sometimes it is just its kinetic energy. • Potential Energy is energy due to the position of the object (Gravitational PE is based on weight and height off the ground GPE = MGH) • Kinetic energy is energy due to the motion of the object (based on mass and velocity KE = ½MV2)

  4. At one point during the Super Bowl, the football had a GPE of 32 J and a KE of 45 J. What was the ball’s ME? • ME = PE + KE • ME = 32J + 45J • ME = 77J

  5. Other Forms of Energy • Mechanical energy deals with the motion (KE) and position (PE) of an object as a whole, but an object can have other forms of energy – both kinetic and potential. • These other forms of energy are associated with the particles that make up objects.

  6. Thermal Energy • The particles that make up objects are called atoms and molecules. They are always in motion (kinetic energy) and are arranged in specific ways (potential energy). • The total kinetic and potential energy of the molecules and atoms in an object is its thermal energy.

  7. Example: Friction • Friction turns mechanical energy into thermal energy • Energy “lost” due to friction still exists – it is now the energy of heat! • Other examples: melting, heating…

  8. Electrical Energy • Electrical energy results from the movement of charged particles. • It can either be kinetic or potential depending on whether the charges are moving or stored. • Examples: batteries, electrical lines, static, lightning

  9. Chemical Energy • Everything is made of chemical compounds(which are made up of atoms and molecules bonded together). • Chemical energy is stored in the bonds of chemical compounds. Breaking and reforming those bonds releases and reorganizes energy. • Example: Food, matches, cells of body, fuel!

  10. Nuclear Energy • Stored in the nucleus (center) of atoms… released during a nuclear reaction • Nuclear Fission: Splitting the nucleus (Nuclear Power Plants  electricity) • Nuclear Fusion: Nuclei join together (Sun)

  11. Electromagnetic Energy • Travels in waves that have some electrical properties and some magnetic properties (hence the name!) • All from the sun (although manmade machines can produce them as well) Examples: microwave, X-ray, radio wave, sunlight, visible light, UV light

  12. Questions • Question: If an object’s mechanical energy is equal to its potential energy, how much kinetic energy does it have? • The object has 0 J of kinetic energy. Since ME = KE + PE then KE = ME – PE. If the ME and PE are the same the KE is 0. • Question: Why do the particles of objects have both kinetic and potential energy? • Particles (atoms and molecules) are always moving so they have kinetic energy and have a specific arrangement in the object (either the arrangement of the chemical bonds or arrangement in the atom) so they have potential energy.

  13. *Law of Conservation of Energy* • Energy cannot be created or destroyed …but it can be transferred and transformed! • The total amount of energy before any transformation is equal to the total amount of energy after

  14. What’s the difference between a transfer and transformation? • Energy Transformation: a change from one form of energy to another form. • Energy Transfer: Energy goes from one object to another as the same form. • This happens whenever work is done to an object… Think about the transfer of momentum

  15. Transform/Transfer Pictures The player transfers energy to the ball as he kicks it Chemical energy of food transformed to kinetic (mechanical) energy of boy

  16. single transformation : one form of energy transformed to another in order to do work Ex: toaster  electrical energy to thermal energy Transformations

  17. Transformations • Multiple transformations: a series of energy transformations is needed to do work (one form of energy to another then another…) • Ex: a match  Striking match (mechanical) causes friction (thermal) this releases the chemical energy in the match which creates fire (thermal and electromagnetic (light))

  18. Questions • Question: What energy transformation allows you to send a rubber band flying across a room? • Elastic Potential Energy  Kinetic energy • Question: Thermal energy is produced when a firefighter slides down a pole. Where does it come from? • Some of the firefighter’s potential energy is transformed into thermal energy through friction

  19. A Common Energy Transformation a. Explain what happens to the kinetic energy and potential energyof a ball as it is tossed up in the air. b. Explain what happens to the kinetic energy and potential energyof a ball as it fallsback to the Earth. c. Explain what happens to the mechanical energy of a ball during the entire toss.

  20. A Common Energy Transformation • Kinetic Energy to Gravitational Potential Energy (and vice versa) Gaining GPE (gaining height) Losing KE (losing speed) Gaining KE (gaining speed) Losing GPE (losing height) Total ME stays the same!

  21. Other KE & PE Transformations • When does this happen? • When anything is thrown up in the air, dropped or falls

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