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ENERGY

ENERGY. THE DRIVING FORCE. What is Energy?. The ability to do work The ability to cause change Measured in Joules, just like work Formula Symbol: E as in E = mc 2. Forms of Energy. Mechanical Energy Describes energy stored and released according to function or force. Forms of Energy.

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ENERGY

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  1. ENERGY THE DRIVING FORCE

  2. What is Energy? • The ability to do work • The ability to cause change • Measured in Joules, just like work • Formula Symbol: E • as in E = mc2

  3. Forms of Energy • Mechanical Energy • Describes energy stored and released according to function or force

  4. Forms of Energy • Electromagnetic Energy • Waves of mostly invisible energy • Includes light, radio waves, X-rays

  5. Forms of Energy • Chemical Energy • Stored and released in the bonds between atoms

  6. Forms of Energy • Nuclear Energy • Stored and released from the nucleus of an atom

  7. Forms of Energy • Thermal Energy • Heat in all its forms and flows

  8. Two descriptions of Energy • Potential Energy • Energy stored by position or condition • Kinetic Energy • Released energy or energy of motion

  9. Potential Energy • The easiest quantified PE is Gravitational PE • This is the PE stored in an object by its height above another reference point • PEGravitational = m g h Joules = kg●(m/s2) ●m Remember, g = 9.8 m/s2

  10. Potential Energy, revisited… • Another form is Elastic PE • This is the PE stored in an object by its being disturbed from its natural state, • and how much it wants to return to that natural state • Good examples: • Springs, swings, pendulums, rubber bands

  11. Kinetic Energy • This is the KE released by an object by its motion • KE = ½ m v2 • Joules = kg●(m/s)2

  12. Problems • A 3.0-kilogram toy dump truck moving with a speed of 2.0 m/s starts up a ramp. How high does the truck roll before it stops? • A 2.0-kilogram ball rolling along a flat surface starts up a hill. If the ball reaches a height of 0.63 meters, what was its initial speed?

  13. Problems • Find the potential energy of this roller coaster when it is halfway down the hill. • A 2.0-kilogram ball is tossed straight up with a kinetic energy of 196 joules. How high does it go?

  14. Law of Conservation of Energy • Energy can not be created or destroyed in normal reactions • Energy can be changed from one form to another • The total amount of energy must be the same before and after a change in energy

  15. Most common energy conversion is from potential to kinetic energy • Gravitational potential energy of an object is converted to kinetic energy as the object falls. • Potential energy can become kinetic and vice versa. • Example: Pendulums

  16. Mechanical Energy in a Pendulum

  17. Energy and Mass • Einstein’s famous equation • E = mc2 • m = mass • c = speed of light (3 x 108 m/s) • Shows that matter can be converted into energy and energy can be converted into mass.

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