<p>Can anyone explain how we know to use the equation of motion for the position and KE graphs of 1e in the 2009 mechanics test?</p>
<h1>1 you just have to recognize the object’s in simple harmonic motion (since U(x) = ax^2), so the graph of x versus t is going to be a sine-/cosine-looking function. x<em>max was already calculated to be 1.3, so just draw a sine curve that has max/min at +/- 1.3 m. The KE curve is going to also be a sine-/cosine-looking function (I guess it’s sine squared or cosine squared). We know KE</em>max is going to be 7.0 J, and whenever the x=+/- 1.3, KE = 0, so just draw the cos squared curve that makes sure all that holds up.</h1>
<p>Can anyone give a an approximate curve for Mechanics and E&M? Especially the former? And how screwed would I be if I didn’t know any gravitation and oscillation? Any equations I should memorize to get by?</p>
<p>one helpful equation I can think of for SHM: a = -w^2 x, T = 1/f = 2pi / w
I thought it would be helpful to memorize the equation of period for a physical pendulum, but 2009 #2 actually had you derive that equation. Darn.</p>
<p>Someone posted the curve for 1998 several pages ago (by the way, this thread more than doubled today, wow!) and it looked pretty generous.</p>
<p>Also, if you don’t know gravitation or oscillation, just hope there isn’t more than one FR on there about it (I’m currently praying that there will be no crazy spring problems). That’s about all you can do, or learn it all within the next 11-14 hours.</p>
<p>last year it was about a 60% according to the AP booklet my teacher was reading from on friday</p>
<p>I guess I just have to be awake enough tomorrow to notice to use sin/cos when I see ax^2</p>
<p>Yeah, I guess. Just remember that SHM means that the restoring force is F = -kx, and F = -dU/dx, so if U(x) is a positive x^2 function, just make the connection. Then again, what are the chances they’ll have a similar problem two years in a row?</p>
<p>Lol thanks. I know a bit of spring stuff from Calc. But yea that physical pendulum question looked brutal. They would not do the same thing twice. Hopefully. </p>
<p>So spring might be doable.</p>
<p>so x(t) = amplitude<em>cos(w</em>t) where w = sqrt(m/k)</p>
<p>And then hopefully I can derive the rest?</p>
<p>That’s essentially all you need (w = sqrt(k/m)). Because you can differentiate x to get v, and v to get a, and then you see “Oh, a also equals -w^2<em>x.” And F=ma, and U=1/2</em>k<em>x^2, E = 1/2</em>k*A^2, and K = E - U.</p>
<p>But it’s when they hook up the spring onto block A, which is on top of block B, and there’s friction between block A and block B, and no friction between block A and the table, and they want to know the maximum coefficient of static friction to keep them accelerating at the same pace, or something crazy like that. Or when they hook up the spring to block A and block B, and block B is jammed against the wall, and for some reason they want you to tell them the period of motion after the spring system has lost contact with the wall from you pushing on block A.</p>
<p>Those are the kinds of things that I DON’T want to see on this test.</p>
<p>the test was hard</p>
<p>what’s on the test free response…what do you predict will be on it? 
if you know what i mean</p>
<p>the mechanics difficulty was medium, but the E & M was Extremely EASY!!!</p>
<p>any ideas what the free response questions could be?</p>
<p>sorry, I cannot disclose information regarding the questions .</p>
<p>wow, i actually felt confident after finishing that test… mc was average, and free response was way easy</p>
<p>Wow. I study non stop all weekend for the exam, but I couldn’t take it becasue my proctor couldn’t find the answer sheet I’m supposed to use. Complete waste of a weekend and a day.</p>
<p>I guess I’ll have to take the exam on the makeup day? Anyone know when that will be? </p>
<p>I WILL be able to make it up won’t I?!</p>
<p>Aren’t all answer sheets the same? Wow, that’s just horrible. In my opinion you should be able to make it up, but I’m not the [almighty] College Board.</p>
<p>I’m actually kind of sad that it’s over now. I’ve been studying for the past week for this test, and now that I’ve finally taken it, life just seems so empty right now. It was like it was my purpose in life was to take that test, and now that I’ve taken it, there’s nothing to do. Maybe I’ll pretend I’m taking AP Chem tomorrow and go work some of their problems. It’s just odd because after AP testing’s over for me, I just give up on school. There’s just no longer any point.</p>
<p>Pretty hard, but I only need a 4 for credit, I’ve had a head cold for a week, it kind of messed me up.</p>
<p>Hopefully when I take Mechanics and E&M in college, I’ll have a better understanding of this stuff… :/</p>
<p>Mechanics FRQ was way too hard. MC was medium to difficult at the least. </p>
<p>This test was nothing like I’ve ever seen in the past…</p>