1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Work Chapter 5 Definition of Work Work is done on an object when a force causes a displacement of the object. Work is done only when components of a force are parallel to a displacement. Work has dimensions of force times length (Nm) which is a Joule (J)

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 5 Definition of Work Section 1 Work

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Practice Pg 162 –Practice 1, 3, 4 Chapter 5 Section 1 Work

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy Chapter 5 Kinetic Energy The energy of an object that is due to the object’s motion is called kinetic energy. Kinetic energy depends on speed and mass.

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 5 Kinetic Energy Section 2 Energy

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy Chapter 5 Kinetic Energy, continued Work-Kinetic Energy Theorem –The net work done by all the forces acting on an object is equal to the change in the object’s kinetic energy. W net = ∆KE net work = change in kinetic energy

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 5 Work-Kinetic Energy Theorem Section 2 Energy

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Practice Problems A 7.00 kg bowling ball moves at 3.00 m/s. How fast must a 2.45 g table tennis ball move in order to have the same kinetic energy as the bowling ball? Pg 166 #1, 5 On a frozen pond, a person kicks a 10.0 kg sled, giving it an initial speed of 2.2 m/s. How far does the sled move if the coefficient of kinetic friction between the sled and the ice is 0.10? Pg 168 #1, 4 Section 2 Energy Chapter 5

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy Chapter 5 Potential Energy Potential Energy is the stored energy associated with an object because of the position, shape, or condition of the object. Gravitational potential energy is the energy an object has because of its position in a gravitational field. Gravitational potential energy depends on height from a zero level and the mass of the object. PE g = mgh gravitational PE = mass  free-fall acceleration  height

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 5 Potential Energy Section 2 Energy

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy Chapter 5 Potential Energy, continued Elastic potential energy is the energy available for use when a deformed elastic object returns to its original configuration. The symbol k is called the spring constant, a parameter that measures the spring’s resistance to being compressed or stretched.

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 5 Elastic Potential Energy Section 2 Energy

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 5 Spring Constant Section 2 Energy

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Practice Pg 172 #1 – 3 Section review pg 172 #1 - 4 Chapter 5 Section 2 Energy

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Conservation of Energy Chapter 5 Conserved Quantities When we say that something is conserved, we mean that it remains constant.

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Conservation of Energy Chapter 5 Mechanical Energy Mechanical energy is the sum of kinetic energy and all forms of potential energy associated with an object or group of objects. ME = KE + ∑PE Mechanical energy is often conserved. ME i = ME f initial mechanical energy = final mechanical energy (in the absence of friction)

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 5 Conservation of Mechanical Energy Section 3 Conservation of Energy

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Conservation of Energy Chapter 5 Mechanical Energy, continued Mechanical Energy is not conserved in the presence of friction. As a sanding block slides on a piece of wood, energy (in the form of heat) is dissipated into the block and surface.

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Practice Pg 177 Practice # 2, 3, 5 Pg 178 Review #1 – 3 Chapter 5 Section 3 Conservation of Energy

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Power Chapter 5 Rate of Energy Transfer Power is a quantity that measures the rate at which work is done or energy is transformed. power = work ÷ time interval An alternate equation for power in terms of force and speed is P = Fv power = force  speed

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Power Standard unit for power is a Watt (W) English unit for Power is a horse-power (hp) Chapter 5 Section 4 Power

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 5 Power Section 4 Power

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Practice Pg 181 –Practice # 1 – 5 –Review # 1, 2 Chapter 5 Section 4 Power