<p>@IIliLL</p>
<p>Yeah B1 required crazy algebra. It was one of the only questions I even attempted. I don’t want to give anything away, but did you run into a problem with the way they defined beta? </p>
<p>I had to redefine beta because my answer could not be written in terms of the defintion for beta they gave. </p>
<p>@ScrewCC, hmm not really, I manipulated it around until I had it in terms of beta (like, it turned into something convoluted like (constant + beta)/(beta^2 - constant), this is just an example, not the actual answer)</p>
<p>I feel like A3 was a lot more unclear about what it was actually asking but yah I agree with you on B1’s algebra bashyness, I used up like 2 scratch papers just for part a</p>
<p>B1 is indeed brutal. But you only need conservation of energy and momentum on a single axis through. </p>
<p>We’re technically not supposed to discuss til april 4th, but…whatever lol
and ya that’s what i did</p>
<p>Hey y’all we can talk about the test now I believe.
A1: not sure, but seems like all you’d have to do for the second part is adjust R to R - h/2*cos(theta)
A2: quadratic formula anyone?
A3: power of a point is what I’ve heard, and Doppler effect for light
A4: ez textbook problem…
B1: some messy expression involving beta in both numerator and denominator as well as a square root
B2: search up relativistic electromagnetism on Wikipedia</p>
<p>@IIIIII The topic covered in B2 is quite rare, I only knew it like a few days ago when reading Griffith’s E&M :))</p>
<p>Btw how do you do the second part of A4? The part where you calculate electric field at the outer shield? And about the second part of A3 do you use Doppler with acceleration? :-? </p>
<p>Electric field inside conductor is always 0… And outside it had nothing to do with charge distribution inside, so same as first part</p>
<p>A3 idk it was weird</p>
<p>And. You’re reading Griffiths? Dang… All i did was skim Purcell lol and basically read Halliday</p>
<p>B1 was the one with the block and the time of flight right? If so all you had to do was use conservation of mass and conservation of energy</p>
<p>I did not think there was not that much algebra. There is no external impulse on the system. Therefore when the block is in the air the whole system is moving at the center of mass velocity, which can be quickly calculated by (M+m)v<em>cm = mv</em>i. After you find the v_cm, you can just apply conservation of energy and find the height reached buy the block, which will then give the time of flight. This is correct right? Since you guys are saying there was so much algebra i hope i didnt over look anything</p>
<p>Also this was my first year taking the f=ma and the usapho exam. Do you guys have any insight on how the exam is graded? Also how many people take the f=ma exam? I am asking this because i hope to get a medal next year and I want to know how good that will look for college admissions. I was just aiming to qualify for usapho this year, which I did, but is that impressive cause I heard that not many people take the f=ma exam.</p>
<p>If you want to impress college adcoms, a medal will probably help, but making team is the real deal. Otherwise, tbh, I’d do the AMC series and try to USAMO instead, as that route has a lot more support along the way, and it’s a lot more well-known (there’s no AoPS equivalent for physics, etc.). Number of participants is something like 4k in F=ma (might’ve grown a bit, but not too much) to 200k+ in AMC, so that’s another big difference.</p>
<p>About B1: yes, that’s the basic rundown, but I’m pretty sure it involved kinematics (to find time), then some square roots, and a whole lot of substitution. There were 4 different v’s to keep track of (initial v, v of block + ball, v of ball afterwards, v of block afterwards), 2 m’s, g, and h.</p>
<p>By the way, time of flight is easy to find. Time it takes the ball to go back to the place it was at at the moment of collision involves a lot more substitution.</p>
<p>I thought height of the big block was negligible so u just had to find the time of flight. I talked to Calvin HUang and he said you could consider the time inside the big block negligible. Calvin Huang made the traveling team last year</p>
<p>The height of the block should be made negligible otherwise you cannot solve it.</p>
<p>Okay, if Huang says so. </p>
<p>But what if the initial velocity is relatively tiny? Then it would spend a majority of it’s time inside the block.</p>
<p>I’m pretty sure the height of the block is negligible as well. From the conditions of the problem, we basically have to assume that how the hole twists inside the block is negligible, since we are not given any information about it.</p>
<p>Whether it spends its time inside the block or above the block makes no difference - we have to assume that it takes a negligible amount of time for the horizontal velocities of the block and the ball to equalize after the “collision” - otherwise, it’s impossible to solve the problem.</p>
<p>Yeah, that’s a lot of negligible stuff - but then again, most mechanics problems are idealized, like this one.</p>
<p>What about A2 (the refrigerator)? …was I right in using the quadratic formula for one of the later parts…?</p>
<p>I don’t remember using the quadriatic formula for A2. But I think there was a equilibrium problem that may have used it, I forgot already.</p>
<p>I’m just mad at myself for making a mistake on B1 part b) because I used the same variable name for two quantities 
(and failed A1 and A3 (did I really just decided to balance forces, when it was obviously torque balance?!). Everything else should be okay, though)</p>
<p>B2 a) derives the formula used in B2 b) (or was it c) ?). 
That was actually very helpful.</p>
<hr>
<p>Giancoli ftw
I don’t think calc-based textbooks are good for studying. Especially when you know calc and you don’t know physics.</p>
<p>When is the finalists list out? My school might have zero or more.</p>
<hr>
<p>A1: balance torque
A2: just some simple thermodynamics thing, with a carnot engine
A3: no idea, this one was kind hard but I sth like \infty and the expected regular value
A4: this appeared harder than A2 at first, until I realized that it was easy
B1: Yeah, try to simplify stuff and don’t mix up v with v_y
B2: B2a) shows how to derive the thing for B2b)</p>
<p>I might be the only one who failed A2… messed a refrigerator with a heat engine :)) </p>
<p>@qwerytiop : Usually early May. Last year it’s 4 or 5 May so you could expecting the same thing this year.</p>