1. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley PowerPoint ® Lectures for University Physics, Twelfth Edition – Hugh D. Young and Roger A. Freedman Lectures by James Pazun Chapter 6 Work and Kinetic Energy

2. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Work, a force through a distance As in the illustration, pushing in the same direction that the object moves Shown in Figures 6.1 and 6.2

3. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Use the parallel component if the force acts at an angle Refer to Figure 6.3. Follow worked Example 6.1.

4. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley How can it be such a great “workout” with no work? When positive and negative work cancel, the net work is zero even though muscles are exercising.

5. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Stepwise solution of work done by several forces Follow the steps to solve Example 6.2. Identify, set up, execute, and evaluate.

6. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley The work-energy theorem—Figure 6.8 Work done on an object can change its motion and energy.

7. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley We can compare the kinetic energy of different bodies Changes in the energy of a moving body under the influence of an applied force change differently depending on the direction of application. Refer to Figure 6.10.

8. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley How fast?—Example 6.3 Read through Problem-Solving Strategy 6.1. See Figure 6.11 below, it corresponds to Example 6.3.

9. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Forces on a hammerhead—Example 6.4 A sketch and free-body diagram to solve the motion of a pile driver

10. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Different objects, different kinetic energies Conceptual Example 6.5 demonstrates the effect of mass. The two iceboats show how velocities are different as masses are different.

11. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Work and energy with varying forces—Figure 6.16 Perhaps the best example is driving a car, alternating your attention between the gas and the brake. The effect is a variable positive or negative force of various magnitude along a straight line.

12. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley The stretch of a spring and the force that caused it The force applied to an ideal spring will be proportional to its stretch. The graph of force on the y axis versus stretch on the x axis will yield a slope of k, the spring constant.

13. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Stepping on a scale—Example 6.6 Whether you like the result or not, stepping on a scale is an excellent example of applied force and the work being done to compress that spring. Follow Example 6.6.

14. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Motion with a varying force—Example 6.7 Refer to Figure 6.22 as you follow Example 6.7. The experiment above and the free-body diagram below it at right.

15. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Motion on a curved path—Example 6.8 If you watch a child on a swing set, you can also consider the motion of a particle along a curved path. While following Example 6.8 you can refer to the swing set and a free-body diagram for the problem. Example 6.9 also follows motion along a curved path.

16. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Watt about power? Once work is calculated, dividing by the time that passed determines power. The pun is credit to James Watt. (You will see that scientists of that era often were privileged to leave their names on the topic of their efforts.) Also note the popular culture power unit of horsepower. The energy you use may be noted from the meter the electric company probably installed to measure your consumption of energy in kilowatt-hours.

17. Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley An example you might do if the elevator is out Refer to Figure 6.28 while following Example 6.11. It’s interesting how a lighter stair climber and heavier stair climber can expend the same power by using different amounts of time.