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Energy

Energy. Chapter 12.3. Learning Target. To distinguish between potential energy and kinetic energy!. Work and energy. Whenever work is done, energy is transferred Energy is the ability to do work Therefore, energy is also measured in Joules!. What is potential energy??.

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Energy

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  1. Energy Chapter 12.3

  2. Learning Target To distinguish between potential energy and kinetic energy!

  3. Work and energy • Whenever work is done, energy is transferred • Energy is the ability to do work • Therefore, energy is also measured in Joules!

  4. What is potential energy?? • What does it mean to have potential? • Potential energy—energy stored due to the position of an object that can be used at a later time “energy of position” • Ex: Stretched back rubber band!

  5. Two Types of Potential Energy • Elastic Potential Energy—energy stored in any type of stretched or compressed elastic material • Ex: A stretched out slinky! • Gravitational Potential Energy—energy stored from the position of an object from the ground • Ex: An apple on a tree branch!

  6. Gravitational Potential Energy • GPE depends on mass and height • Equation to know: • Gravitational Potential Energy = mass x free-fall acceleration x height • PE = mgh g = 9.8 m/s²

  7. Gravitational Potential Energy Practice! • A 65 kg rock climber ascends a cliff. What is the climber’s gravitational potential energy at a point 35 m above the base of the cliff? • PE = mgh • PE = (65kg)(9.8 m/s^2)(35) • PE = 2.2 x 10^4 J

  8. Kinetic Energy • Remember the kinetic theory? • Kinetic energy  energy of a moving object due to the object’s motion • KE depends on mass and speed • Equation to know: • KE = ½mv²

  9. Kinetic Energy Practice! • What is the kinetic energy of a 44 kg cheetah running at 31 m/s? • KE = ½mv² • KE = ½(44kg)(31 m/2)² • KE = 2.1 x 10^4 J

  10. Kinetic and Potential Energy • Law of Conservation of Energy energy cannot be created nor destroyed, just rearranged • Hence, potential energy is converted into kinetic energy!

  11. Bill Nye?

  12. Practice! • http://www.staff.fcps.net/AWEGER/science/document/qefworksheet.pdf

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