October 2011 - Physics Discussion

<p>Physics was rough… I ended up completely running out of time and not getting back to a good half of the questions I initially skipped but wanted to go back to on my first pass through the test. Hopefully the curve saves me.</p>

<p>Yeah, not much physics takers. Anyone know when scores come out?</p>

<p>It takes like 3 weeks or so if I remember correctly. Anyways, I’m probably canceling my scores.</p>

<p>@ Rennir - It was the sharpest one. The charge is concentrated in the pointy tip because identical charges naturally repel. Thus, electric field would be greatest there. Think about lightning rods. Lightning strikes the sharp tip.</p>

<p>I’ve been conversing to one guy about it over PM. He asked about like 10 problems and I gave responses to the ones I knew (or at least thought I knew). Below are his questions followed by a dashed line and then my responses (the first one I answer after the question). </p>

<p>What did you get for the energy vs distance graph? Was potential energy “a” and kinetic “b-a”? I told him I put a, then b. </p>

<p>What did you put for the ruler attached to the clamp? Was it simple harmonic motion?</p>

<p>Do you remember any of these:</p>

<p>frequency stays the same if the wavelengths are the same
light bulb question w/ switch-- switch didn’t affect the answer?..but i forget the number
light bulb question w/ switch-- stays at same brightness (A)?
which one was not a standing wave on the rope?
ohm’s law
scientific matching section – why does heat go from hot to cold?
4 m/s^2 for acceleration of the block being pulled
mu is 1/6 (what were the other two answers for the accelerating to a stop along 2m friction?)
another question with 0 < x < 20… or something
question with 0.05 and 0.10
wire creates a magnetic field
3 and 1 for the tensions
Alpha particle – D – given table
Work question … (75)(60)(60)/(2000)
Amplitude is lower as sound wave moves from speaker
18N …. 72/4 = 18N
vector addition question - which graph was it?
electron jumping energy levels – four different possibilities?</p>

<hr>

<p>I put simple harmonic motion. I don’t remember the other options but I remember excluding some because the acceleration of the end would not be constant. </p>

<p>Yeah, I think that one was that the frequency of the light must be greater than the sound wave because we know speed=wavelength x frequency, and we know that the speed of light is greater than that of sound and their wavelengths are equal so the light’s frequency must be larger. </p>

<p>I wasn’t sure on the switch one. I was just talking to one of my friends and he knew the capacitor questions and I think he’d know that one, too. I’ll ask him next time I get a chance. </p>

<p>I really wasn’t sure on the standing wave, either. All I could eliminate was the one that was flat because that could be a standing wave of n=2 or something (I’m terrible with fundamental frequencies). I think I narrowed it down to b and d or something because I knew it couldn’t be one of them but I ended up omitting it.
The answer to the “which of the following does this demonstrate” was ohm’s law, I’m pretty sure. I brought it down to ampere and ohm, but i put ohm.
I remember putting down something for the hot to cold one, I think it was the entropy choice.
I don’t really remember the accelerating block question, more details and I may remember.
The one with the block stopping, the second one was 18N I’m quite sure. I answered the first one, too, but I don’t remember the question or what I put. I’d be happy to explain why I put 18N if you’d like.
I don’t remember that one.
Oh, I remember the .05, that was the one asking what happens to the force when you half the distance or something, I think I put 1/4F, which was A, maybe.
I don’t know what you’re asking on that one. Do you remember something about a particle (it was definitely an electron) going into an electric field and it asked what the direction of the magnetic field must be for the particle to remain with a constant velocity (ie no net force), I thought about it for a while and then I put down, which was opposite the electric field.
I remember two masses connected by a rope and the top mass was connected to the ceiling, I think I put the combined m*g and something else, that was an easy one, though. I’m not sure what you’re asking for the 3-1 tensions, maybe that was it.
Alpha particle was definitely D, yeah, I remember putting C and then checking it over and being all “wow, I’m a dumbass”. Mass goes down 4, atomic number goes down 2.
I’m quite sure I put that as well, the 75 60 60 thing, because watts are joules per second…oh wait, I think I had them all multiplied, you have them divided by 2000, I don’t remember the question, just multiplying by 3600 to get to hours, but where did the 2000 come from? I don’t remember?
I don’t remember that problem, I may have ran out of time (I’m talking about the speaker one).
Vector additions? It was the only one that went up and to the left (the slope would be high negative), you could figure that by do head to head addition of the vectors.
Do you remember the question about the computer graphing that guys’ velocity? I put the one that didn’t cross the x axis put was positive for all of x.
I’m having trouble remembering what I put, I remember drawing them all out, but then realizing the emission would be the same for all of them, plus, they asked about the absorption, not emission, I’m thinking I put 3, though. 1 to 2, 1 to 3, 2 to 3. But, I’m not sure.</p>

<p>For the pair of satellite questions (the diagram took up almost the whole page):</p>

<p>One question was the greatest energy of one type or the other? The second question was the greatest velocity. I think I put E (shortest radius and greatest mass) for both. Anyone?</p>

<p>Yea I got the same answers for the satellite one.</p>

<p>I found this test hard too…Usually I finish practice tests with 15 minutes left to check my work.
I finished right on time on the real one and wasn’t able to fill in the 4 or 5 I omitted.</p>