Official 2011 AP Physics C Thread

Test Preparation AP Sciences
1

<p>C deserves its own thread :)</p>

<p>Discuss anything relevant to the exam, such as prep books, advice, etc.</p>

2

<p>I’ll start by listing a typo / questions I found in the PR book Practice Test 2.
Solution for number 66 is off - p.542. Also, the answer is questionable IMO… </p>

<p>Anyone want to help me on number 54? I don’t get the direction of force on loop…
Click on the 2nd thing here…
Book: [Cracking</a> the AP Physics C Exam, 2011 … - Google Books](<a href=“CRACKING THE AP ENVIRONMENTAL SCIENCE EXAM(2011 EDITION) - Princeton Review - Google Books”>CRACKING THE AP ENVIRONMENTAL SCIENCE EXAM(2011 EDITION) - Princeton Review - Google Books)</p>

3

<p>is it C?</p>

<p>Because the magnet moves to the left, the magnetic field strength decreases. Therefore, the induced current want to make a force that follows the magnet to the left to its original orientation with the magnet so that the magnetic field strength does not decrease.</p>

4

<p>Hey, does anybody know how well the Princeton review book’s practice exams can predict your score on the AP. My friend and I have been looking at released exams and scoring well on them, but when we tried to time ourselves on Princeton, we didn’t do very well (not finishing on time and getting lots of the questions wrong). Should we be worried at all?</p>

5

<p>umm one of the practice exams in PR is scarily similar to a released exam, so sort of…</p>

6

<p>How much is the average % of the physics C exam should you get right to get a 3/5 anyone? Thanks :)</p>

7

<p>@cooly, my teacher said if you can get around 60% on the MC, and then 50-60% on the FR then you have a 5. </p>

<p>But that was last year, with the guessing penalty.
I’m guessing it might be a bit higher this year since everyone will be guessing, so everyone’s raw score should be a bit higher? I dunno.</p>

8

<p>Any AP physics C mechanics veterans have any advice for a test taker next Monday?</p>

9

<p>Is there always a lab question where you have to set up an experiment?</p>

10

<p>Any released Ap exams from the past? like 2010 C mechanics?</p>

11

<p>@Mikeypz Thank you so much :)</p>

12

<p>anyone have cram or review packets? thanks</p>

13

<p>

</p>

<p>I remember seeing one for mechanics on a past frq, but no for e&m so far.</p>

<p>Also, cram packet would be useful :slight_smile: though you could basically go through the equation sheet they provide and look up the concepts in the formulas to study :)</p>

14

<p>They may make you do a linear fit for data they give you, I wouldn’t expect anything more complicated than that. I took the exams last year.</p>

15

<p>Score Calculator:</p>

<p>[AP</a> Physics C Score Calculator](<a href=“http://www.free-test-online.com/ap/ap_physicsc_score.html]AP”>http://www.free-test-online.com/ap/ap_physicsc_score.html)</p>

16

<ol>
<li><p>a charged particle is projected parallel to a uniform to a magnetic field, the resulting path is a straight line parallel to the field… why?</p></li>
<li><p><a href=“http://tinyimage.net/images/50136173150204648365.png[/url]”>http://tinyimage.net/images/50136173150204648365.png&lt;/a&gt;
The answer is A and A explain please?</p></li>
<li><p>How do you know which formula to use for the energy stored in the capacitor (you know there’s 1/2QV and 1/2V^2C…) like for number 61 in <a href=“http://tinyimage.net/images/82840419860896498375.png[/url]”>http://tinyimage.net/images/82840419860896498375.png&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;
<li><p><a href=“http://tinyimage.net/images/85261815545593376175.png[/url]”>http://tinyimage.net/images/85261815545593376175.png&lt;/a&gt;
umm the answer is A, and I have no idea what to use…</p></li>
<li><p><a href=“http://tinyimage.net/images/61071039590674115839.png[/url]”>http://tinyimage.net/images/61071039590674115839.png&lt;/a&gt;
WHAT WHY IS ISN’T IT 2uJ? THIS DEFIES PHYSICS WAHHH jk lol</p></li>
<li><p><a href=“http://tinyimage.net/images/49749004950847017201.png[/url]”>http://tinyimage.net/images/49749004950847017201.png&lt;/a&gt;
I’m guessing you use kirchoff’s law for this…</p></li>
<li><p><a href=“http://tinyimage.net/images/00194558680517153372.png[/url]”>http://tinyimage.net/images/00194558680517153372.png&lt;/a&gt;
so i get why 66 is B, but why is 67 B as well??</p></li>
</ol>

<p>

</p>

17

<ol>
<li><p>Because the initial velocity of the particle is parallel with the field it experiences a
force = Bqv(sin0)=0 N.
This means the particle experiences no force and continues with the same trajectory.
Remember that magnetic field has to be perpendicular with velocity to cause a force.</p></li>
<li><p>To know when the electric field is least in magnitude, conceptualize when the force acting on a test charge would be least because F=qE. Using this technique, you can see that if a + point charge is placed at A then it will not move because it experiences a net force of zero and therefore the electric field there is zero.</p>

<p>For the second part, its a trick question. Potential is a scalar quantity therefore it has no direction. So to find the potential at a given point, do the SUM of kq/r due to all charges. This sum is greatest at A because r (the distance from the charge to A) is the smallest.</p></li>
<li><p>Use Q^2/2C if its in series, .5CV^2 if its in parallel </p></li>
<li><p>This is a question about Lenz’s law. Basically the loop ALWAYS induces a current that opposes the change in magnetic flux that caused it. So if the loop’s magnetic flux is increasing, the loop wants to prevent that change and induce a current in a direction that will create a force on the loop that pushes it back to the left. So here, the loop induces a current that flows counterclockwise. Now because a current carrying wire experiences a force in a magnetic field, you can do right hand rule and see that the loop will get pushed left.
To dumb it down A LOT, if the loop’s magnetic flux changes in anyway, its going to experience a force opposite to the way its moving because of the induced current. This entire process can be used again for the second part of it leaving the magnetic field. Here you see the magnetic flux is decreasing so it experiences a force to the left (because of the induced current) so that its magnetic flux doesn’t decrease.</p></li>
<li><p>TRICKY ass question, the magnetic force created by a magnetic field is perpendicular to both velocity AND the magnetic field. If the force is perpendicular to the velocity then the force does no work on the particle because W = Fdcos(90) = 0. </p></li>
<li><p>is it D? just add the potential differences in the middle branch and you get -12V and the question asks for magnitude so = 12v. </p></li>
<li><p>Easy question, the electric field at x=0, or when the position is directly in the middle of the ring, is zero. Think about it in force terms, if a test charge is placed in the middle of the ring it wont experience any force bcause all the elements on the ring will be pushing on it equally. And if the force = 0, E=0 because F=qE.
The only graph with E=0 at x=0 is B.</p></li>
</ol>

18

<p>does anyone have a cram/review guide? if so please post or pm me</p>

<p>thanks and good luck on AP Physics C Exam!</p>

19

<p>I found this: [AP</a> Physics C Formula Sheet - Study Together with JoyNotes - Study Together, Do better.](<a href=“http://joynotes.net/document/75/ap-physics-c-formula-sheet]AP”>http://joynotes.net/document/75/ap-physics-c-formula-sheet)</p>

<p>Anyone got anything better?</p>

20

<p>about 88 out of total to get 4. 120 and above for a 5</p>