1. Work and Energy

2. Doing Work What is work? Using a force to transfer energy to an object causing the object to move in the direction of the force.

3. Doing Work Work = force x distance W=fd

4. So work is force times distance W = f·d or Joules = Newtons · meters Same work, different force 100 feet 200 feet 200 feet x 1000N = 200,000 J 100 feet x 2000N = 200,000 J

6. What is energy? Energy is the ability to do work Potential energy The energy stored in objects because of their position Kinetic energy The energy in objects that are in motion

7. What is energy? Energy is the ability to do work Kinetic energy KE = m·v² 2 20kg · (20 m/s) ² 2 20kg · 400m ² /s ² 2 8000kg · m ² /s ² 2 4000kg · m ² /s ² = 4,000 J

8. Kinetic energy KE = m·v² 2 5kg · (10 m/s) ² 2 5kg · 100m ² /s ² 2 500kg · m ² /s ² 2 250kg · m ² /s ² = 250 J 10kg · (10 m/s) ² 2 10kg · 100m ² /s ² 2 1000kg · m ² /s ² 2 500kg · m ² /s ² = 500 J

9. Kinetic energy KE = m·v² 2 5kg · (10 m/s) ² 2 5kg · 100m ² /s ² 2 500kg · m ² /s ² 2 250kg · m ² /s ² = 250 J 5kg · (20 m/s) ² 2 5kg · 400m ² /s ² 2 2000kg · m ² /s ² 2 1000kg · m ² /s ² = 1,000 J

10. Kinetic energy A snail with a mass of 5g, traveling at.014 m/s has 0.00000048 J of kinetic energy An 18-wheel truck traveling at 26.69 m/s (43 mph) has 2,200,000 J of kinetic energy

11. Potential energy The energy stored in objects because of their position Gravitational Potential Energy Using force to do work against gravity The energy is stored until gravity can do work on it and pull it down to the ground

12. What is energy? Gravitational Potential Energy GPE = weight · height (why weight and not mass??) 150g · 2m = 300 J 300g · 2m = 600 J 150g · 4m = 600 J

13. Transferring Energy between Potential and Kinetic

14. 100% Potential 0% Kinetic

15. 50% Potential 50% Kinetic

16. 0% Potential 100% Kinetic

17. 50% Potential 50% Kinetic

18. 100% Potential 0% Kinetic ?

19. 50% Potential 50% Kinetic

20. 0% Potential 100% Kinetic

21. 50% Potential 50% Kinetic

22. 100% Potential 0% Kinetic

23. 50% Potential 50% Kinetic

24. 0% Potential 100% Kinetic

25. 50% Potential 50% Kinetic

26. 100% Potential 0% Kinetic

27. 50% Potential 50% Kinetic

28. 0% Potential 100% Kinetic

29. 100% Potential 0% Kinetic

30. 50% Potential 50% Kinetic

31. 0% Potential 100% Kinetic

32. 50% Potential 50% Kinetic

33. 100% Potential 0% Kinetic

34. 0% Potential 100% Kinetic

35. 100% Potential 0% Kinetic

36. 0% Potential 100% Kinetic

37. 100% Potential 0% Kinetic

38. 0% Potential 0% Kinetic

39. Forms of Energy Mechanical Energy Since potential and kinetic energy can easily switch between them we measure the combined energy and classify it as mechanical energy.

40. Forms of Energy Thermal The kinetic energy due to the random motion of the particles that make up an object Which would have more thermal energy; an ice cube, a lake, or a boiling pot of water? The lake because it has so many more particles than the other two therefore more thermal energy.

41. Forms of Energy Chemical The energy of a compound that changes as its atoms are rearranged Chemical energy is a form of potential energy The total energy depends on the arrangement of the atoms in a compound Which has more chemical energy; water or sugar? Sugar has more chemical energy because of its large molecules (C 6 H 12 O 6 )

42. Forms of Energy Electrical Energy The energy of moving electrons Electrical energy is produced when magnets are moved through coils of wire

43. Forms of Energy Sound Energy The transmition of vibrating energy through the air A vibrating object causes the particles around it to vibrate. This kinetic energy is transmitted to our ears and we hear sound

44. Forms of Energy Light Energy The energy produced by the vibrations of electrically charged particles e−e−

45. Forms of Energy Light Energy The energy produced by the vibrations of electrically charged particles e−e−

46. Forms of Energy Light Energy The energy produced by the vibrations of electrically charged particles e−e− Photon of light

47. Forms of Energy Nuclear Energy The energy that comes from changes in the nucleus of an atom Atoms store a tremendous amount of potential energy because of the position of the particles in the nucleus When the nucleus of an atom is “split” we have nuclear fission This is the same energy given off by an atomic bomb

50. Forms of Energy Nuclear Energy The energy that comes from changes in the nucleus of an atom Atoms store a tremendous amount of potential energy because of the position of the particles in the nucleus When two or more atoms are force together to make a new atom it is called fusion Fusion how the sun produces its energy