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The Nature of Energy

The Nature of Energy. Physical Science Ms. Pollock 2008-2009. What is energy?. Involved in every change Energy – ability to cause change Electrical, chemical, radiant, or thermal All different forms of same thing Object in motion or at rest Conversion from one form to another.

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The Nature of Energy

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  1. The Nature of Energy Physical Science Ms. Pollock 2008-2009

  2. What is energy? • Involved in every change • Energy – ability to cause change • Electrical, chemical, radiant, or thermal • All different forms of same thing • Object in motion or at rest • Conversion from one form to another

  3. Kinetic Energy • Objects in motion • Kinetic energy – energy of a moving object due to its motion • Dependent on mass and speed • Kinetic energy (in joules) = ½ mass (in kg) X speed (in m/s2) • KE = ½mv2 • SI unit joule

  4. Kinetic Energy Example • A jogger whose mass is 60 kg is moving at a speed of 3 m/s. What is the jogger’s kinetic energy? KE = ½mv2 KE = ½(60 kg)(3 m/s)2 KE = ½(60 kg)(9 m2/s2) KE = 270 J

  5. Potential Energy • Objects not in motion • Potential energy – stored energy due to position • Converted to kinetic energy when motion occurs • Elastic potential energy – energy stored in something that can stretch or compress

  6. Potential Energy • Chemical potential energy – energy stored in chemical bonds • Gravitational potential energy – energy stored by objects due to their position above Earth’s surface • Gravitational potential energy (J) = mass (kg) X acceleration of gravity (m/s2) X height (m) • GPE = mgh

  7. Gravitational Potential Energy Example • What is the gravitational potential energy of a ceiling fan that has a mass of 7 kg and is 4 m above the ground? GPE = mgh GPE = (7kg)(9.8 m/s2)(4 m) GPE = 274 J

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