<p>I dunno. This may be irrelevant, but i didn’t realize there was a question #7 on Physics B when I took it - too used to the 6-question Bio, Compsci, Calculus, Chemistry format. I didn’t answer it. It was the easiest question. I got a 5. lol.</p>
<p>^^Yes. 5 is ~55%, 4 is ~45%, 3 is ~35%.</p>
<p>Gah, I wish I remembered my linalg. >_< Oh well, calculus works just fine.</p>
<p>I had to create an account to reply to the conversation about whether use of linear algebra/higher order mathematics is appropriate on the AP exam.</p>
<p>In terms of grading, it absolutely is - Ologos, you won’t be counted off for using more sophisticated methods of solving a diffeq than the average Physics C student would even be aware of. However, it’s important to note that the likelihood of receiving partial credit for a wrong answer found by using these methods is very slim. The grading rubrics are specifically designed to break down an answer derived from calculus, and the graders aren’t going to spend a lot of time reinventing a new rubric for your method. From what it sounds like, you probably got it right, so don’t worry about that.</p>
<p>Energize, I would expect the curve to more resemble 5~50%, 4~40%, and 3~30% this year for mechanics. The FRQ was pretty difficult for me, and I had been getting 43/45s on the more than 15 past FRQs we did in class for review. This year’s was probably the most challenging yet, and it wasn’t offset by a truly simple MC.</p>
<p>How did you calculate B from the graph?</p>
<p>nvm, technically it hasnt been 48 hrs yet</p>
<p>Been a while CC.</p>
<p>… So, theoretically speaking, that would mean that you could miss all the free response, but get all the multiple choice right and still get a 5. Not that it’s going to happen…</p>
<p>I am just glad AP exams are over, regardless of everything.</p>
<p>ologos-- you make me feel so dumb. I read about linear algebra earlier this year, but I didn’t think about during the exam. <em>Sigh</em> Well, at least at my school you only need a 3 for credit, but I really wanted a 5. E&M it is still possible, but Mech, no way… At least I have a backup plan if I failed. I don’t think I did THAT badly, but you never know.</p>
<p>Here is to self-studying! Worthwhile, even if didn’t work!</p>
<p>puggly123- at least you don’t have to deal with the frustration of knowing all the material for E&M, but forgetting and not focusing because you were frustrated with Mech. Then, you remember immediately after the exam what you should have done… AARGH! If I end up not getting a 5 on E&M, (or if I don’t pass at all) it doesn’t get more irritating than that. When I remembered, I had Metallica’s “Fade to Black” ringing in my ears. Can’t point fingers, though. That was my dumb fault there. I guess I should look for positives in this though. Never get angry during the test. Better now than college. Lesson learned. And it also means that if I do need to take a placement test over it, I do know the material. </p>
<p>Luckily, when it comes to physics C, either one, never underestimate the curve. I am not saying be overly giddy or hopeful, but don’t write yourself off. You have to remember that you are on CC, and a lot of kids would have found it harder then most kids here. And whatever happened happened. I heard of a guy who left half the free response blank(no answer, units, nothing) and still got a 3 or 4…don’t remember which. That was just hearsay though, take it as you will. Multiple choice will be my savior here on both. </p>
<p>On a different note, I am under tornado warning right now… after what happened in Alabama, this isn’t good… Excuse this hastily written post.</p>
<p>“Never get angry during the test.”</p>
<p>Omg, that was me. I was so ****ed at the CB during the FR section that I couldn’t even focus. Lolz</p>
<p>Also, I probably left ~1/2 of the FR section blank.</p>
<p>I had to really compose myself after Mech to get in the groove for E&M. I had post-test nerves, and had to try and forget about the Mech test. It kind of worked…</p>
<p>“Never get angry during test.” Amen. Like I said, lesson learned, and really a waste of energy when you think about it. I just won’t do it again. I probably should have learned that a long time ago, but better late than never, I suppose. It’s irritating to lose points over that, but better than not knowing the material. So I guess I should be relieved? How confusing.</p>
<p>Then again, knowing the material is useless if you can’t or won’t remember it when you need to. </p>
<p>I think you’ll be fine. I hope so. I am not just saying that. Gut feeling, puggly123. :)</p>
<p>pioneerjones-good job. Wish I did the same.
I managed to put an answer for everything, but I already know some of them aren’t right.</p>
<p>Whatever the case, I will review this stuff to make sure I actually know it. Like I mentioned earlier, I self-studied this in limited time, so I can’t take the risk that I missed something. 
The credit is nice, but I do have a backup plan for that, as I said before, so knowing it is what I am concerned with.</p>
<p>On the positive side, my other AP exams I am feeling pretty confident about. And I am the first from my school to be taking the C exams… so I guess that is an achievement in itself. I guess that is also why I still really want to do well, despite what I tell myself about the credit.</p>
<p>I don’t want to know what the answers to the free response are yet, strangely enough. I really don’t for any of the subjects. Dunno why. I had a chance with BC Calc(did really well on it) earlier, but I couldn’t bring myself to do it. Any theories?</p>
<p>So the Free Response questions are up on the AP website:</p>
<p><a href=“Supporting Students from Day One to Exam Day – AP Central | College Board”>Supporting Students from Day One to Exam Day – AP Central | College Board;
<p>1a. t = J/F
b. m = Jp / V
c. m(v<em>x)^2 / 2 …(i wrote this with the m and didn’t realize I solved for m in part b…will I lost points?)
d. m(v</em>x)^2 / (2d)</p>
<ol>
<li>Fn perpindicular, Fg straight down
b. didn’t realize that they wanted it in terms of the components of the diagram…I ended up using conservation of energy: mg (3R/4) + mg(Rsin(theta)) = 1/2 mv^2 then solved for mv^2 / R to get the centripetal force. ended up getting mv^2 / R = 2mg (sin theta + .75)
c. right set up but wrong equations (i used conservation of energy but forgot the mgR of the string… >.< thus, my answer was messed up
d. right set up but wrong answer from 2c (could only use my messed up value for V_d
e. only was able to draw a graph decreasing and concave up</li>
</ol>
<p>3a. d^2 theta / dt^2 = -b theta
b. T = sqrt(I/b) - I was being dumb and didn’t put the 2 pi because I thought it was the rotational analog between the mass spring and torsion pendulum.
c. Plotted the correct graph
d. T^2 = 130 I + 3 or something
e. Since I forgot the 2 pi on part b, I got a different value for Beta then correct answer. However, my procedure was correct.
f. I said that basically even if there was no mass, there would still be a period (sqrt 3 in this case)</p>
<p>Can someone predict how many points I will get on this free response??? I managed to answer most every question but I just forgot the other ones (like 1e and 2e differential part) </p>
<p>I’m not very good at judging point values so it is making me very nervous =(</p>
<p>Yeah… that’s not good.</p>
<p>yea you probably got 25</p>
<p>Answers!!! - are we allowed to post them now?</p>
<p>Can’t. I am too depressed about my own. Sorry. :(</p>
<p>I have a bad feeling about Mech, even with the curve now…</p>
<p>Got to hit the physics book.</p>
<p>yea I had to edit my thing…any other predictions? I feel like I got 15ish… >.< hopefully they are more lenient with earlier incorrect answers leading to later ones?</p>
<p>I made the same mistakes you did. For 1 e I got dn=(FtD/Fb) because work done on the bullet should equal the work done by friction because the average force is what is pushing the block</p>
<p>did people get 7/12 for 2d?</p>
<p>and that’s almost what i got for 1e.</p>
<p>i started with Fb(d-dn)=FtD
then solved for dn
i didn’t offer much in terms of logic though.</p>
<p>xdrgnh,
that’s interesting, because it assumes that ALL of the energy in the collision goes towards moving the block. but that disregards the energy that is just plain lost to heat in the collision (you can’t make a hole in a block with no energy).</p>
<p>I do not understand how the first d they give you plays a role in 1 e I’m hoping they put that in just to trick people</p>
<p>Anyone else want to give me a score prediction? 
lol</p>
<p>My procedure/thought process for #1 Mech:</p>
<p>For (a) and (b), v is v_x</p>
<p>(a) J=Ft, so t=J/F
(b) J=mv, so m=J/v
(c) Work done in stopping the projectile is the change in kinetic energy. KE=.5mv^2, so it’s .5(J/v)v^2, which is .5Jv
(d) Work is equal to average force times distance. So .5Jv=Fd. So F_b=.5Jv/d
(e)/(f) I know that the impulse imparted by the projectile on the block is equal to something, which I wrote on the test for both parts. Hopefully I get points.</p>
<p>Same for #2 Mech:</p>
<p>(a) 2 forces, normal and gravity. Gravity straight down, Normal perpendicular to surface
(b) Screwed this one up, said Mgcos(theta). Maybe I’ll get something for writing normal=centripetal?
(c) Conservation of energy from point A (all gravity potential) to point D (all kinetic). h for mgh is 7R/4.
(d) I only remember getting 7/12 for my coefficient of friction. Which might not even be what I put. 
(e) i. -kv=m(dv/dt)
ii. Integrate
iii. Initial acceleration (i.e. at point D) is kv/m (even though I only put v). Concave up, decreasing, horz. asy. of acceleration equals 0.</p>
<p>For Mech. #3 (a=alpha, B=beta, O=theta):</p>
<p>(a) Ia=-BO. Replace a with double derivative of theta with respect to time and divide I over.
(b) Using small angle approximation, alpha=-(angular velocity)^2 times theta. Angular velocity is sqrt(B/I). Period=2pi/angular velocity. Could also use mass on spring analogy, with m=I and k=B.
(c) Graph.
(d) My slope was like 160, y-int .20. y=160x+.2 or T^2=160I+.2
(e) Checked my calculator, got .247. Units are same as that of spring constant.
(f) No clue.</p>