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Work and Energy

Work and Energy. Dr. Robert MacKay. Clark College. Introduction. What is Energy? What are some of the different forms of energy?. Energy = $$$. Overview. Work (W) Kinetic Energy (KE) Potential Energy (PE) All Are measured in Units of Joules (J) 1.0 Joule = 1.0 N m. W.

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Work and Energy

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  1. Work and Energy Dr. Robert MacKay Clark College

  2. Introduction • What is Energy? • What are some of the different forms of energy?

  3. Energy = $$$

  4. Overview • Work (W) Kinetic Energy (KE) Potential Energy (PE) • All Are measured in Units of Joules (J) • 1.0 Joule = 1.0 N m W KE PE

  5. Overview • Work Kinetic Energy Potential Energy Heat Loss W KE PE Heat Loss Heat Loss

  6. Work and Energy • Work = Force x distance • W = F d • Actually • Work = Force x Distance parallel to force d=4.0 m W= F d = 6.0 N (4.0m) = 24.0 J F= 6.0 N

  7. Work and Energy • Work = Force x Distance parallel to force d= 8.0 m F= 10.0 N W = ?

  8. Work and Energy • Work = Force x Distance parallel to force d= 8.0 m F= 10.0 N W = 80 J

  9. Work and Energy • Work = Force x Distance parallel to force d= 8.0 m F= - 6.0 N W= F d = -6.0 N (8.0m) =-48 J

  10. Work and Energy • Work = Force x Distance parallel to force d= 6.0 m F= - 5.0 N W= F d = ? J

  11. Work and Energy • Work = Force x Distance parallel to force d= 6.0 m F= - 5.0 N W= F d = -30 J

  12. Work and Energy • Work = Force x Distance parallel to force F= + 6.0 N d= 8.0 m W= 0 (since F and d are perpendicular

  13. Kinetic Energy, KE • KE =1/2 m v2 m=2.0 kg and v= 5 m/s KE= ?

  14. Kinetic Energy m=2.0 kg and v= 5 m/s KE= 25 J • KE =1/2 m v2

  15. Work Energy Theorm • KE =1/2 m v2 • F = m a

  16. Work Energy Theorm • K =1/2 m v2 • F = m a • F d = m a d

  17. Work Energy Theorm • KE =1/2 m v2 • F = m a • F d =m a d • F d = m (v/t) [(v/2)t]

  18. Work Energy Theorm • K E=1/2 m v2 • F = m a • F d = m a d • F d = m (v/t) [(v/2)t] • W = 1/2 m v2

  19. Work Energy Theorm • KE =1/2 m v2 • F = m a • F d = m a d • F d = m (v/t) [(v/2)t] • W = 1/2 m v2 • W = ∆ KE

  20. Potential Energy, PE • Gravitational Potential Energy • Springs • Chemical • Pressure • Mass (Nuclear) • Measured in Joules

  21. Potential Energy • Gravitational Potential Energy = weight x height PE=(mg) h m = 2.0 kg 4.0 m

  22. Potential Energy PE=(mg) h PE=80 J m = 2.0 kg 4.0 m K=?

  23. Conservation of Energy Energy can neither be created nor destroyed only transformed from one form to another Total Mechanical Energy, E = PE +K In the absence of friction or other non-conservative forces the total mechanical energy of a system does not change E f=Eo

  24. Conservation of Energy PE=100 J K = 0 J m = 1.02 kg (mg = 10.0 N) Constant E {E = K + PE} Ef = Eo PE = 75 J K = 25 J 10.0 m PE = 50 J K = 50 J PE= 25 J K= ? No friction No Air resistance PE = 0 J K = ?

  25. Crib Sheet

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