Housekeeping…

1. Chapter 9 - Energy

2. Housekeeping… • Vocabulary quizzes must be taken by Saturday. • Exam 1 begins Friday morning (perhaps earlier…working on this one) • Exam 1 deadline: Monday 11:00 am (for a fee later on Monday or on Tuesday) • Wednesday and Friday REVIEW. • PLEASE come to class with questions and/or email questions to me beforehand. Chapter 9 - Energy

3. 250 0 I read the chapter before coming to class. • Yep! • Well, more than half of it. • A little but not half. • None or practically none. Chapter 9 - Energy

4. 0 of 250 Which statement best describes your feelings about the upcoming exam over Unit 1? • I’m not really that worried about it. • With some studying, I think I’ll do just fine. • I’m worried that even if I study hard I won’t do so well. • I’m really nervous about it. Chapter 9 - Energy

5. Conservation of Energy • Total energy is conserved. But energy can and does change forms. What forms can it have? • Two major classes: Mechanical and Internal. • Mechanical deals with the motion and position of large objects. • Internal deals with the motion and position of atomic sized objects. Chapter 9 - Energy

6. Types of Mechanical Energy • Kinetic Energy= Energy from motion • K. E. = mv2/2 A vehicle has more kinetic energy when it is more massive or moves faster. Chapter 9 - Energy

7. 250 0 10 You are walking down the sidewalk at 3 mph. You then start running at 6 mph. By how much did your kinetic energy increase? • It didn’t increase • Two times • Three times • Four times (K. E. = mv2/2) Chapter 9 - Energy

8. Potential Energy = Energy from position Gravitational Potential Energy = mgh(“g” is the acceleration caused by gravity) m h Types of Mechanical Energy Objects have more GPE when they are more massive or farther from the earth. Chapter 9 - Energy

9. Types of Mechanical Energy • Electrical Potential Energy = Energy from charge separation Objects have more EPE when the charge is greater and when the separation is greater for opposite charges or less for like charges Chapter 9 - Energy

10. Total Energy K. E. G. P. E. Transformation of Energy Gravitational Potential Energy  Kinetic Energy A ball tossed in the air Chapter 9 - Energy

11. 0 of 250 10 Where is the kinetic energy the greatest in a pendulum? • At the bottom of a swing. • At the top of a swing. • It is unchanging with time Chapter 9 - Energy

12. m m Gravity distance Work: The Process of Transforming Energy • Work equals force × distance • We do work when we go against a force. Chapter 9 - Energy

13. You must go against a force • Work is done here but not here Chapter 9 - Energy

14. Types of Internal Energy • Thermal: the energy of heat Chapter 9 - Energy

15. Heat Transfer • Radiation • The energy itself travels through space Sunrise Chapter 9 - Energy Laser

16. Heat Transfer • Convection • Heat material and the material moves then gives up the heat. Yellowstone Hot Pot Chapter 9 - Energy

17. Chapter 9 - Energy

18. Heat Transfer • Conduction • Heat moves through the material but the material itself does not move or deform. Chapter 9 - Energy

19. Heat Transfer • Passing buckets between stationary people is like conduction. • People running back and forth with buckets is like convection. • Spraying directly from a well is like radiation. Chapter 9 - Energy

20. Types of Internal Energy • Chemical Potential Energy: From atomic bonding and interactions. Lots more on this when we get to the chemistry section. Chapter 9 - Energy

21. Types of Internal Energy • Elastic Potential Energy: From deformations Chapter 9 - Energy

22. Types of Internal Energy • Nuclear Potential Energy: Very potent because the nuclear interaction is so strong. Chapter 9 - Energy

23. Examples of Energy Transformation • Bullet fired into the air • Car stopping at a stop sign • Pole vault • Making TNT Chapter 9 - Energy

24. Relativistic Energy and Mass-Energy Equivalence • Mass and Energy together are conserved. • Mass can turn into energy by the proportion of the speed of light squared. That is… E = mc2 Chapter 9 - Energy

25. 250 0 10 Energy can be defined as: • A measure of destructive capability. • The ability to exert a force on an object while it moves through some distance in the direction of the applied force. • Both 1 and 2. • None of these. Chapter 9 - Energy

26. 250 0 10 If you move two positively-charged objects closer together, then electrical potential energy • increases. • decreases. • stays the same. Chapter 9 - Energy

27. 250 0 10 If you move two oppositely-charged objects closer together, then electrical potential energy • increases. • decreases. • stays the same. Chapter 9 - Energy

28. 250 0 10 As you bounce a ball, which of the following is conserved? • Gravitational potential energy • Kinetic energy • Internal energy • Total energy • More than one of the above • None of the above Chapter 9 - Energy

29. 250 0 10 If an object has kinetic energy, then it must • be electrically charged. • be moving. • be in an elevated position. • be as low as possible. • be at rest Chapter 9 - Energy

30. 250 0 10 Work is always done on an object when • More than one force is applied. • The object moves at a constant speed in a straight line. • A force moves the object through a distance in the direction of the force. • All of the above. Chapter 9 - Energy

31. 250 0 10 If you’re skiing downhill, which of the following must be true? • Your internal energy decreases. • Your kinetic energy increases. • Your gravitational potential energy decreases. • You fall. Chapter 9 - Energy