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Lecture 6: Work and Energy
September 7, 2017
Reading Assignment
 Read: Chapter 6
 Study: Figs 6.3, 6.4; Exs 6.1, 6.2, 6.4; Fig 6.14; Eq 6.14; Ex 6.6
 Ignore: “Power and Velocity” on p. 103
Objectives
 (Continuing objective) Relate concepts of classical mechanics to “everyday” situations and discuss various applications of the concepts to practical problems in various fields of science, medicine and engineering.
 From a given constant force and the straightline motion of an object, calculate the work done on the object by that force.
 Determine the work done during onedimensional motion from a forcevsdisplacement graph, or by integration of $F(x)$.
 Apply the workkinetic energy theorem to a moving object subject to one or more forces.
 Understand the definition of power, and be able to relate power, work, and time.
Homework
 Friday's Assigned Problems:
A73; CH 6: 6, 14, 15, 21, 25, 31, 41, 48, 83
Answers: CH 6 #14 $490\,\text{J}$; CH 6 #48 (a) all 1, (b) all 0
 Monday's HandIn Problems: A14, A17, A18; CH 5: 36, 38, 46; CH 6: 22, 30, 40; Supp CH 1: 2
Lecture Materials
 Click here for the Lecture overheads
or here for fullsized versions.
Answers to conceptests: (1) a  3, b  1, c  2, d  2, e  2; (2) 2; (3) 2; (4) 3
 Click here for information about meditation and mindfulness sessions and classes
Videos of example problems
To see the problem statement, click on the link below. To play the video example, click on the underlined words "Video Demonstration" near the top of the page with the problem statement. Video Example #1: A straightforward application of the workkinetic energy theorem. ans: 48 N.
 Video Example #2: Calculating the work done by a spatially varying force. ans: 760 J. Note: the answer provided in the video, 787 J, is incorrect. All of the steps in the video are correct except for the arithmetic done to get last line.
SlowMotion Videos of Dropping Spring
The following are some movies that a couple of PHYS 211 students made of the dropping spring (see problem A15).Dropping of a "magic spring," in slowmotion (courtesy of Isaac Briefer). Watch the bottom of the spring! pic.twitter.com/2K5EoVy2Es
— Tom Solomon (@TheChaoticBird) September 7, 2016
And here's a slowmotion video from another PHYS 211 student. Again, watch the bottom of the "spring!" pic.twitter.com/z9s2IHaDc8
— Tom Solomon (@TheChaoticBird) September 7, 2016
PreClass Entertainment

(I'll probably cut one of the following songs; haven't decided which one yet.)
 Don't Cry, by Seal
 Dreams, by the Cranberries
 Don't Be Cruel, by Elvis Presley
 Dangerous, by Big Data (featuring Joywave)
 Days Are Forgotten, by Kasbian
 Default, by Django Django