<p>I think I got the first one, but IDK if its right.</p>
<p>The graph showed the negative velocity. The form of the velocity equation for springs is v(t) = - W(Xm) (sinWt + phi). Since there was no phase shift in the velocity graph, phi = 0.</p>
<p>W = 2pi / period, so I looked at the graph and found the period (I think the period may have been 7). From this I solved for W (2pi/7 = .898). W(Xm), the coefficient of the function, is simply equal to the amplitude shown on the graph (around .7). I think the answer i put for velocity was v = -.7sin(.898t) or something around there. </p>
<p>For the next parts of the problem, I used these same constants to get the position and acceleration equations. </p>
<p>I hope that was right…</p>
<p>for 1a I got v(t)= -0.16sin(8.98t)</p>
<p>actually, i think my numbers matched david’s. the period was .7 and the amplitude was 1.6 not what i said above.</p>
<p>etothepie that sounds a lot like how I did it. But the period was .7. amplitude was .16</p>
<p>I just realized I really messed up… I forgot to switch signs…</p>
<p>yea desfanido and ilovediana i think i got what you guys got. i just forget now what the period and amplitude were.</p>
<p>amplitude was 0.16 right? and period was 0.7</p>
<p>Yeah
I got the same
This is how I did
Might be wrong but i tired…
The period was when velocity went from 0 and back to zero
and i set that equal to 2pi/(omega) solved for omega and that was what when inside the sine function
i remember getting -1.6sin(8.7t) or something along those line
Part B was just a simple integration.
part C i didn’t have time to finish…
and D and E where pretty easy since they where just FBD and for the graph it was a damped oscillation. ( or at least i think it was since there was friction given that it was a “rough” surface)
let me know what you guys think of my solution
any corrections, comments etc,</p>
<p>When are the scoring guidelines for the FRQs released?
Also, any predictions for the mechanics curve?</p>
<p>Multiple choice wasn’t too hard, it was actually very easy compared to Frqs.
FRQ’s where almost lethal so i would estimate.
55-100% for a five
45-50% four
35-40% Three
just an educated guess based on previous exams.
Hopefully even lower than that, but only time will tell.</p>
<p>Anyone figure out FRQ #3 ? I don’t see how to apportion friction between rotational and translational simultaneously. </p>
<p>@semaphore12: I honestly think a self study for E&M would be easier. Once you get past the unfamiliarity of looking at charges in open fields (instead of familiar looking blocks on familiar looking ramps) the conceptualization of it all is a lot easier. This past semester my Physics C teacher went of E&M stuff in class, but it helped almost no one. I co-self studied and began not paying attention to my teacher’s lectures (aka. a skimmed through Powerpoint). I feel like I ACTUALLY understand the material and have been getting A’s and B’s on the tests (before the curve; avg test scores are usually in 40’s 50’s or 60’s). If you have the motivation to learn it to actually understand it then I highly encourage a self study. [What I studied from: [Viren’s</a> Videos Free AP Physics Review Help](<a href=“http://www.apphysicslectures.com%5DViren’s”>http://www.apphysicslectures.com) ] Also, take into account that most of those teaching it in high school will not be that great at it… sadly…</p>
<p>maxgphysics94, are you serious??? haha I actually went to a score calculator and I think I might have a low 5. Basically it’s possible to beast the mc and then get lazy and only do the easiest FRQ and still get a 5. </p>
<p>That curve is downright stupid. Either there’s a problem with physics education in America, or physics is a harder subject than I’m giving it credit for.</p>
<p>Can Someone tell me about the 2nd question on the Mechanics FRQ (the one with gravitational energy conservation experiment). Can you use a low friction pulley here to do this experiment by holding the system stationary and release it then finding the acceleration of the system and using vf= vi + at then timing this with a stopwatch for time. and solving for the final v for the kinetic energy at the end. would this be wrong i was inclined to doing the experiment this way bc i felt like this was a trick quesition and soon as i saw this on the list of items.</p>
<p>This is how my textbook modeled it: [imgur:</a> the simple image sharer](<a href=“http://imgur.com/lG0Tp]imgur:”>Imgur: The magic of the Internet)</p>
<p>The first FRQ the amplitude was 0.16 but the period was something like 0.54
T = 2pi / w
w = 2pi/0.54 = 3.70pi
v = 0.16cos(3.70pi x t)</p>
<p>nerdyjew: you did not pay attention to the spacing on the x axis. Also, never use x unless you mean cross product from now on.</p>
<p>what was the spacing on the x axis?</p>
<p>The spacing was even by 0.1. You did something funky to end up with 0.54, it was 0.7. I can see how that might have happened though. That is the kind of error I always make, nothing conceptual :-).</p>
<p>what were some specific hard multiple choice questions for mechanics?</p>