<p>I am currently reviewing the whole course on my own right now. My AP class is starting magnetism soon, but I am still shaky on the easier topics in mechanics. While doing some practice problems in chapter 4 (Work, Energy, Power) I came across a few questions I want to get sraight. Please help me.</p>
<li><p>How do you know when to use the work-energy theorem (W=delta k) and the conservation of mechanical energy (ki + Ui = Kf + Uf)? How can you distinguish which one to use?</p></li>
<li><p>[Chapter 4, #9] If the rock lost have of its gravitational energy at the middle due to its height, shouldn’t the kinetic energy go up by a factor of 2 according to the conservation of mechanical energy? I would think that if kinetic goes up, potential goes down, and vice versa.</p></li>
<li><p>[Example 5.4 on page 77] In the solution on the next page (page78), where do you get J (change in momentum) from the graph? In other words, how did PR get 0.14 N*s from the graph/problem? I don’t know where they got the value from.</p></li>
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<p>Please help clarify these things for me. I don’t think I can move on until I understand it well. THanks!</p>