<p>@xeqxeqxeqxeq yep those were them!</p>
<p>I bombed the FRQ for form G Mechanics… except for the lab. The lab was easy.</p>
<p>E&M FRQ were just terrible. I kept hesitating on Gauss’s law on the first question because I didn’t know I could cancel the Length of the cylinder when finding the electric field :(. The Second one was worst, I knew we had to do a differential equation for the the time constant because they gave up the voltage and time table, but I didn’t store the formulas in my calculator <em>sob</em>. I was surprised to find out that we had to transform the voltage graph to a linear one though; never done that before other than transforming least square regression lines. The last one was involving magnetic fields was pretty easy actually. I should have reviewed E&M more lol; I was doing Angular problems all week so I’m pretty confident with Mechanics.</p>
<p>JohnAndTequila - agreed. </p>
<p>Arion231 - Watch W.L MIT 8.02 lectures. I mastered gauss’s law cause of them.</p>
<p>~Score Curve dance</p>
<p>@arion231</p>
<p>I just included height in there with a made up h and it did end up cancelling for me.
I just had faith it would work out lol</p>
<p>So I hear they release the free response questions tomorrow, is that at midnight? 2am? 5am? Anyone with AP test experience know? (This was my first one)</p>
<p>It’s usually sometime in the middle of the day, not at midnight.</p>
<p>It will be released at 4 pm Wednesday the 15th.</p>
<p>It’s out!
[AP</a> Central - The AP Physics C: Electricity and Magnetism Exam](<a href=“Supporting Students from Day One to Exam Day – AP Central | College Board”>AP Physics C: Electricity and Magnetism Exam – AP Central | College Board)
[AP</a> Central - The AP Physics C: Mechanics Exam](<a href=“Supporting Students from Day One to Exam Day – AP Central | College Board”>AP Physics C: Mechanics Exam – AP Central | College Board)</p>
<p>So anybody figured out how to find the time constant for #2d?..</p>
<p>For #2 on E&M this is as far as I got:</p>
<p>ai) B
aii) parallel with the Capacitor</p>
<p>bi) graph lnV and time (is this right? and does lnV have units? I put Volts)
bii) Fill row with lnV values</p>
<p>c) Graphed the downsloping linear graph</p>
<p>d) no idea, stopped here. I didn’t do this but something like -1/(slope)?</p>
<p>ei) I wish I did this without the value, but part d value = RC, solve for R
eii) time constant goes up, make the slope less steep?</p>
<p>MoldyBrick, yes that is how I did the problem. Everything there is correct in method. The time constant was in fact -1/(slope). But the unites of ln V should have been unitless actually, because then the units of the slope are 1/seconds, making the time constant in seconds once you take the inverse and negate it. I managed to get this all during the test, but admitedly this was a tricky problem. I didn’t like the fact that you couldn’t really do anything if you didn’t figure out that you had to plot t against ln V.</p>
<p>Mechanics #3, is this how you guys did it:
a. Sum of torques=0, FaR-FtR=0, Fa=Ft
Sum of forces=0 Fa+Ft-mg=0
2Fa=mg
Fa=10 N</p>
<p>b. Torque: FaR-FtR=1/2MR^2(a/R)
Fa-Ft=1/2ma
Ft=Fa-1/2ma
Force: Fa+Ft-mg=ma
2Fa-mg-1/2ma=ma
2Fa-mg=3/2ma
24-20=3a
a=4/3 m/s/s</p>
<p>c. w=w0+a/Rt
w=4/3<em>10</em>3=40 rad/sec</p>
<p>d. i didn’t take into account potential energy but E=mgh+1/2mv^2+1/2Iw^2
and solve for h and v using given values</p>
<p>e. less than because rotational inertia of the hoop is greater than the rotational inertia of the disk</p>
<p>Predicted curves on this test?</p>
<p>Wait…I just looked at the collegeboard questions for mech and I had completely differents FRQs
I had 1. terminal velocity, 2. momentum, 3. experimental rotational problem</p>
<p>@Gradient, you had a different form.</p>
<p>Why is there not a lot of AP Physics C test takers?</p>
<p>@Jamison Ok cool, I wish I had followed through but I kept doubting myself >.<</p>
<p>@SAT EDIT: nvm</p>
<p>Any other thoughts guys. I thought it was a hard test overall…Everyone else agrees right?</p>
<p>@SAT200:</p>
<p>a) same as you
b) mg is not a torque, so why did you use it in sum of torques? I wasn’t sure of myself on this one, so you may be correct. I ended up with a = 2m/s^2
c) I did it the same way except the radius was 0.1m, not 10m? Also I think units should be degrees/sec, but I’m unsure about that as well.
d) I did E = mgh + 1/2 Iw^2 I don’t think you need translational kinetic energy because the disk is not slipping.
e) same as you</p>
<p>I’m really unsure about part b and about units on part c. Hopefully this question will not mark down points for units… lol</p>