<p>How many of you are ready for Monday? I was feeling ready until I took this practice exam today and failed. :(</p>
<p>I hate inertia. Am I the only one?</p>
<p>Inertia’s fine. I hate rolling objects</p>
<p>^Really?</p>
<p>A hoop and a disk with the same outer radius and mass roll starting from rest down a inclined plane of angle 30 degrees and a non-zero coefficient of friction. Which of the following is true?</p>
<p>A) The hoop gets to the bottom first.
B) The disk gets to the bottom first.
C) The hoop and disk get to the bottom at the same time.
D) Without the exact coefficient of friction, it can’t be known which object gets to the bottom first.
E) Without the height of the plane, it can’t be known which object gets to the bottom first.</p>
<p>Is it B, the disk?</p>
<p>a hoop has more inertia so it will have a smaller speed K=1/2Iw^2. The answer is B.</p>
<p>More precisely, a disk has more ROTATIONAL INERTIA (I = moment of inertia), so it’ll get to the bottom first. </p>
<p>My weak points for this test are:
- Springs (sheesh)
- Oscillations and pendulums
- Knowing what equations to use on rotation problems.</p>
<p>What about you guys?
Btw, any of you doing E&M right after the Mechanics too?
I am…feeling better about it than Mechanics.
I’ll be happy with 4’s on both.</p>
<p>AxeBack, my “weak points” are exactly the same as yours.</p>
<p>I have Bio then both Mech and E&M… I’m screwed for all 3.</p>
<p>Lol Cleer, glad we’re on the same page!</p>
<p>And having all three on the same day sucks, dude. You’ll be worn out by the time you reach part II of E&M (eat a ton in between Bio and Mechanics, there’s some people doing this in my school too).</p>
<p>Btw just curious, for those taking Mechanics only, did you guys have a year-long course in Mechanics? I wish I did, because that would’ve meant tons of practice throughout the year. I had one semester of Mechanics and the second semester E&M.
Really worried about these two APs (my last and hardest this year).</p>
<p>Lol, im screwed for air resistance, because I never learned it?
is it on the test? is it hard?</p>
<p>
[QUOTE=azzajack]
Lol, im screwed for air resistance, because I never learned it?
is it on the test? is it hard?
[/quote]
</p>
<p>Yes but its pretty easy.
You deal with it just like any other force.
Make sure you realize if its a kinematics or F=ma problem before starting though…you might end up confusing yourself halfway through.</p>
<p>Btw, anyone know if buoyancy is on the test?</p>
<p>For me its a self-study so I never really taught myself Gravitation or Oscillations.
Everything else is okay except rotation is pretty tough.
I was looking at free response questions on college board and whenever gravitation comes up its just using basic formulas given.
And someone gave me some free-response questions from 2002 and they are a lot easier than the past few years.</p>
<p>I have Bio then Physics B then Physics C. ■■■ =(</p>
<p>I hate rotational motion with a passion :mad:</p>
<p>How are you taking Physics C and B in one day?</p>
<p>sorry for those with bio, m, and em</p>
<p>that really blows…i have the first two</p>
<p>i can’t get credit for this though so it’s pretty much bio im worried about</p>
<p>^ why are you taking them then?</p>
<p>Rotation isn’t THAT bad, the hardest part is figuring out what equations to use. Most of the time, energy will work. Total energy = Rotational kinetic energy + Linear kinetic energy - (whatever due to friction; again, static or kinetic…you’ll probably be given the coefficients), same goes for angular momentum and angular acceleration.
As long as you’re not mixing up translational and rotational motions, you’ll do fine.</p>
<p>Hey guys i have a question. Which inertia equations should I memorize?</p>
<p>My teacher told me to only worry about: hoop, disk and cylinder about a perpendicular axis.</p>
<p>any thoughts?</p>
<p>Guys, it seems all of you are REALLY stressed/worried. The cutoff score for a 3 is like 30 +/- 4 out of 90. THATS RIGHT…30/90…awesome huh.</p>
<p>For a 5: on the two practice exams I’ve taken in class it was a 49/90 :D</p>
<p>Uh, I’m kind of ditsy on oscillations and calculating Rotational Inertia. Oh ya, gravity is pretty annoying seeing as we JUST covered gravity…AFTER E&M!!! Oh well, I feel confident for a 4</p>
<p>^ Who wants a 3?</p>
<p>We all want 5’s.</p>
<p>^ no duh. and I’m taking bio, physics c mech, e/m…■■■</p>