MAY 2013 PHYSICS THREAD (question pool)

<p>@yukihime29:</p>

<p>pretty sure person not involved in light & sound was copernicus</p>

<p>and yeah air resistance is right i think, because while air resistance wouldn’t cause discrepancy AMONG the trials, it would cause a discrepancy between the EQUATION (which says that the acceleration is constant the whole time) and the TRIALS.</p>

<p>what about

  • the one with the magnet moving through the coil/circuit
  • “what’s probably wrong with the way this circuit is hooked up?” (i said ammeter but i’m doubting that was right)</p>

<p>Ammeter is correct. It was connected in parallel. Ammeters are NEVER connected in parallel or they give the wrong reading.</p>

<p>That’s good, I didn’t get question wrong!!! What about the water tank question? For the first one I said 20 degrees but upon retrospect I think I messed up because I didn’t use the thermodynamics equations I just looked at the graph, the actual temperature probably depend the amount of each substance, correct?
Got the throwing ball on a moving train was the answer same?</p>

<p>the moving train one i said was the same because in the reference frame of people in the train nothing changes. and i said 20 degrees because there was no choice that said “it depends on the size of the room” so i guess we’re assuming the room is big enough that the heat lost by the tank will only make a negligible difference in the room temp (so then the equilibrium temp would just be the room temp)</p>

<p>Oh man that was pretty decent. It’s easier after Physics C, btw. But some of those questions really threw me off… and at 48 seconds a question, there’s no time to lose. =/ #timingproblems</p>

<p>@ solipsisme thats good what did you get for the 2nd question of the two? </p>

<p>Also did anyone get a string of Es around 4-5?</p>

<p>^Which question are you referring to?
And I vaguely recall some string of E’s at some point, yeah.</p>

<p>What about those random magnetic field line graph questions? Did you get C A E?</p>

<p>uhhh 8x10^6 i think? because it was losing approx 10 degrees/min at that point, and it was 8x10^5 J / degree, but i’m not completely sure. and i also don’t remember if i got a string of Es.</p>

<p>What about the question asking for the effect on gravitational force when the diameter of the planet is doubled? F<em>g=GMm/r^2, so F</em>g should be 1/4th of the original. But that wasn’t an answer choice.</p>

<p>@PiquantPeppers it stays the same. funny that this same question was discussed in this thread BEFORE the test… If only I’d come here before the test…</p>

<p>No, because the actual radius of the planet doesn’t matter, it only matters if the distance from the planet core to the moon changes. So you could have a bigger Earth, but if the distance between the moon and the center of the Earth (which is “r” in the equation) remained constant, F_g would remain constant.</p>

<p>(I’m glad they didn’t put 1/4th as an answer choice or else I would’ve probably been stuck deciding which one to pick, haha)</p>

<p>^PiquantPeppers YES exactly. I put unchanged. Since when you think about that, the distance between the two centers of the planets didn’t actually change.</p>

<p>wow that was embarrassing… Don’t know why I didn’t realize that.</p>

<p>Does anyone have anything on why sounds gets quieter as you get farther, though?</p>

<p>I said damping because i know damping = amplitude loss = quieter sound, but i’m not sure if that’s actually what happens in nature.</p>

<p>Also, the closed organ pipe?</p>

<p>I didn’t know the falling question either, but that was the answer choice that I picked. O.o
What was the o organ pipe question I don’t remember?</p>

<p>Organ pipe one I picked the trajectory path right above the horizontal path answer. Initially it goes up and then continues in a parabolic path. </p>

<p>What about the magnet/solenoid question- the effects on the current as the magnet enters and as it leaves?</p>

<p>I don’t get that one but if you Google b field through a solenoid then you’ll find pictures</p>

<p>^PiquantPeppers I picked the SAME DIRECTION one…</p>

<p>I put same direction as well. How about the prism that scatters the visible light, asking for the reason red angled the least?</p>

<p>ah wait by organ pipe i meant the node antinode things. i believe there were two problems, and for one of them i put 50 Hz for the frequency of the closed pipe when compared to the 100 Hz open pipe (feeling ambivalent though) and the other one i put 1:1 for the ratio of nodes to antinodes (which i think is right).</p>

<p>the spiral pipe one i said it goes straight tangential to the path (B, i think) in the spiral because there is no force on it to keep it moving in a tangential path, so it would just go straight due to inertia. (i think i also learned in class that when a thing falls out of circular motion it goes straight in a tangent direction, but idk if that still applies)</p>