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Energy Continued

Energy Continued. Unit 5 – Lecture 2. Review: PE & KE. Potential Energy – “stored” E Kinetic Energy – energy of motion / “released” E. Conservation of Energy. Law of Conservation of Energy: energy can neither be created nor destroyed in normal reactions

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Energy Continued

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  1. Energy Continued Unit 5 – Lecture 2

  2. Review: PE & KE • Potential Energy – “stored” E • Kinetic Energy – energy of motion / “released” E

  3. Conservation of Energy • Law of Conservation of Energy: • energy can neither becreated nor destroyed in normal reactions • energy can be changed in form from one to another • initial energy = final energy • energy in = energy out • aka 1st law of thermodynamics

  4. Mechanical Energy • Mechanical E – total amount of PE & KE in a system • as PE decreases, KE increases • as PE increases, KE decreases • what kind of relationship is this…direct or inverse?

  5. Mechanical Energy Equation: • MEinitial = MEfinal • (PE + KE)initial = (PE + KE)final • (m g h + ½ m v2 )initial = (m g h + ½ m v2 )final

  6. Mechanical Energy • ME in a pendulum:

  7. Practice At which point… • is GPE at a maximum? • why? • is KE at a maximum? • why?

  8. Practice Which of these describes E? [any] • Ability to do work Ability to cause change • Ability to increase energy Ability to decrease work Joules is NOT a unit for which of these? • PE KE • Force Work

  9. Forms of Energy • Mechanical Energy • energy of an object due to its motion [kinetic E] or position [potential E]

  10. Forms of Energy • Electromagnetic E • waves of mostly invisible E • light energy often is converted into thermal E • can be converted into chemical E through photosynthesis

  11. Forms of Energy • Chemical E • stored and released in the bonds between atoms • food, batteries

  12. Forms of Energy • Nuclear E • stored and released from the nucleus of an atom

  13. Forms of Energy • Thermal E • heat in all its forms and flows • recall – exothermic & endothermic • transferred through conduction, convection, & radiation

  14. Forms of Energy • Electrical E • separation and movement of electrons • [not really a form of E on its own – it is a combination of forms of Mechanical and Electromagnetic E]

  15. Practice • When you are watching tv, what energy conversions are taking place? • Which energy transformation takes place when a match is struck against the side of a matchbox and bursts into flames? • What causes you to hear something? What kind of energy is sound?

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