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Energy

Energy. Physics December 9/12/13. Objectives. Define mechanical energy Define kinetic and potential energy Describe the work-energy theorem State the law of conservation Evaluate how energy is conserved Evaluate a proof for the work-energy theorem. Topic Energy. Facts

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Energy

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  1. Energy Physics December 9/12/13

  2. Objectives • Define mechanical energy • Define kinetic and potential energy • Describe the work-energy theorem • State the law of conservation • Evaluate how energy is conserved Evaluate a proof for the work-energy theorem

  3. Topic Energy Facts The “something” that enables an object to do work Measured in Joules (J) We will focus on mechanical energy What is Energy?

  4. Topic What else have we learned that is measured in Joules? Facts Work Reach for the Stars

  5. Topic Mechanical energy Facts The energy due to the position (potential energy) of something, or the movement (kinetic energy) of something What is Mechanical Energy?

  6. Topic What does it mean when someone says you have a lot of potential? Facts Making Connections

  7. Topic Potential energy Facts Energy stored and held in readiness Something at rest Something high off the ground Symbol is PE Units are Joules (J) PE = mgh m = mass (kg) g = gravity (10 m/s2) h = height/distance (m) PE= potential energy (J) Potential Energy

  8. Topic Kinetic energy Facts Energy of motion Symbol is KE Units are Joules (J) KE = ½ mv2 m = mass (kg) v = velocity (m/s) KE = kinetic energy (J) Kinetic Energy

  9. Topic A car parked on the street. A car driving down the street. A rock falling from a mountain. Facts PE KE KE Potential or Kinetic Energy?

  10. Topic What is the relationship between work and energy? Facts Whenever work is done, energy changes Work = change in Energy Work-Energy Theorem

  11. Topic Use the equation for work and PE to show how I can say: W = PE Facts W = PE Fd = mgh since W = Fd Since PE = mgh mgd = mgh Since F = mg *which are the same Reach for the Stars

  12. Topic When is energy conserved? Facts ENERGY IS ALWAYS CONSERVED! Energy is transferred from PE to KE and vice versa Conservation of Energy

  13. Topic Figure 8.7, page 110 Facts Let’s take a closer look at the conservation of energy

  14. Topic Why don’t I get hit in the face? Facts Explain the teacher demo

  15. Topic Remember when we dropped things. What was the initial velocity before dropping? Why then is something at rest have no KE? Facts Making Connections

  16. Topic Use the following words to describe what is happening with the swinging pendulum. PE KE Conservation of energy Work Work-energy theorem Facts Closing

  17. Topic Can anyone prove why: Fd= ½ mv2 Note: ignore the 1/2 Facts Challenge

  18. More Practice- on website! • Use the equations for PE and KE to solve PE = mgh KE = ½mv2 • Handout #5, 6, 8a

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