<p>I guessed on that. i was thinking 45 too but i just chose the answer that sounded the best -_-</p>
<p>anyone think the curve will go up or down for this test because of the no penalty rule?</p>
<p>All right, well, I’m going to bed now.
Hopefully someone can make Torque alllll clear to me, or show me a website with great explanations, haha.</p>
<p>Good night guys, good luck tomorrow!
Remember to look for those MC patterns.</p>
<p>@ Abrayo yeah in my class we argued about that problem for about 30 mins and never came to a good answer. we found tons of problems that the AP test got wrong.</p>
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<p>I was referring to 24. But, yes, you’re right, 23 was E.</p>
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<p>Remember, Torque is the cross product of the distance and Force. (FrsinTheta). For problems where the bar is attached to a wall and held by a string. This is in static and rotational equilibrium. So the sum of the forces is 0 and the sum of the torques is 0. That should be enough to solve the problem for whatever the question asks.</p>
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<p>Hmmmmmm…
well, the distance traveled is going to be Vo^2 * sin(2theta) / g, so when we graph the sin(2theta) function, the max occurs at 45 degrees. But I don’t see why the answer is C…</p>
<p>EDIT: Wait! I think I do. Wow, why the heck would they even ask this question. Anyway, the key part here is that it is from a **cliff<a href=“aka%20uneven%20ground”>/B</a>, so the equation I mentioned earlier becomes a bit more complicated, actually, a lot more complicated. The whole problem comes in because when we look at the range equation, we let y0 = 0, so the solutions of the equations for time are just t=0 (the beginning) and t= 2vsin(theta)/g…BUT, when we include the y0, then we must use the quadratic equation, and we get a different range equation, which results in a bunch of messy algebra.</p>
<p>Point being, when a projectile is launched from a height not equal to 0, the critical angle (angle that gives the maximum distance) is not 45 degrees, rather, it is <45 degrees. </p>
<p>Which makes the answer C.</p>
<p>Anyway, I’m done for the day. Get some sleep and good luck guys!</p>
<p>Don’t lose the faith, guys! Remember the curves are very much in your favor, even after being adjusted for the guessing thing. Also, for the projectile thing, there are a few useful equations that can be derived easily, but just to show you:</p>
<p>Range = (V^2)sin(2x)/g</p>
<p>Maximum height = (V^2)(sin^2(x))/2g</p>
<p>Also, to the person who wrote that they are messing up on the problems and, if I understand correctly, is getting only 5/15 b/c they mess up at the beginning- remember to plug in whatever answer you can if part B requires the answer from A. Even if you can’t do A, write something for A and plug it into B and you will get full credit for B!</p>
<p>Just edited my take on the projectile problem, btw.</p>
<p>Hey Wongton. I hate to creep, but it’s cool to see another future Cornellian in this thread. I’m headed to Cornell engineering next year, too!</p>
<p>Anyway, best of luck, everyone. My final bit of advice: if you have no idea what the electric field for a given radius is, just write zero!</p>
<p>Hmm, okay @ the projectile one. I definitely wouldn’t think of that on the exam though.</p>
<p>Regarding torques in that situation - how do you apply torque to the rod? Is it Frsintheta, where r is the length, f is the weight of everything on the bar, and . . . sin 90? So you end up with weightsxlength?</p>
<p>Oh God how do you do 8 and 9?
<a href=“http://www.laphysics.com/physicsap/tests/rotation/rotation.pdf[/url]”>http://www.laphysics.com/physicsap/tests/rotation/rotation.pdf</a></p>
<p>^ I’ve gotta go, but for number 8 it’s just the net torque = 0. So it’s the torque generated by the man minus the torque from the weight of the bar (r=center of mass of the bar, which is right in the middle) minus the torque (with an unknown force) from the cable (remember it’s only the vertical component that matters). Then you solve for the force.</p>
<p>See if you can do the other one similarly.</p>
<p>Last minute physics tips, anyone? on multiple and free-response…?</p>
<p>^, free response predictions?</p>
<p>please no rotational motion questions… xD</p>
<p>last minute review on coupled motion, anyone? totally forgot how coupled motion works…</p>
<p>and what do you do on the designing your own experiment FRQs?</p>
<p>^Does Physics have those?</p>
<p>I’m looking at the 1999 physcs C mechanics part c question… its a design your own thing.</p>
<p>and the solution is vague. it pretty much gives points if you have a procedure that uses all the materials given that will work… but how do I know it will work? xD</p>
<p>oh crud. our teacher gave us a chart of what topics showed up each year from 95 to 09 and rotational/rolling motion is on all but one year -__-</p>
<p>It seems like induction and circuits and e-fields are almost always all going to be on the frq for e&m</p>