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Work and Energy

Delve into the fundamentals of work and energy with Dr. Robert MacKay from Clark College. Learn about different forms of energy, such as kinetic and potential energy, and how they are measured in joules. Explore the concept of work as force multiplied by distance, and discover the relationships between work, kinetic energy, potential energy, and heat loss. Gain insights into the conservation of energy and the calculations involved in determining mechanical energy. This comprehensive guide provides a solid foundation in the principles of work and energy.

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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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