<p>^Why is it so hard to believe -16? I mean the math II curve is a pretty generous curve too (ok, not to the same extent, but still). Physics is a rather notoriously hard subject for most people.</p>
<p>It very well could be, but I refuse I believe it wholeheartedly until I see an actual test previously administered that had -16 as it’s curve.</p>
<p>At any rate, the pump problem explicitly stated it was an ideal machine, meaning it had 100% efficiency. 110J of energy went into it, so 110J came out.</p>
<p>Do any of you remember a I, II, III type question with a very skewed elliptical orbit? The choices were acceleration stays constant, angular momentum is conserved, or something like that.</p>
<p>I think I put angular momentum is conserved for that one, which I believe was choice III. Does anyone else remember?</p>
<p>It was angular momentum, yes.</p>
<p>For the guitar one, it was a 3 part question. I was increase in tension, which is true, II is change in frequency, which I wrote as true but wasn’t 100% sure, and III was wavelength i think, don’t remember, and I don’t remember what I put for that either.</p>
<p>It asked for the ones that stayed constant, in which case the answer was wavelength only.</p>
<p>^Can you guys explain the angular momentum one, i left it blank. Also, i think i got wavelength as well.</p>
<p>And the BB test was administered in 2003 i believe lol</p>
<p>The angular momentum question was a I II III question. It had a picture of a satellite with elliptical orbit, and it asked which components of the satellite remained constant. The options were potential energy, velocity, and angular momentum. Only the last one was correct.</p>
<p>^Yeah i know the question, but like can you explain why angular momentum is correct? I just like to know things for future reference :)</p>
<p>Is it because of conservation of angular momentum?</p>
<p>Angular momentum is conserved in a system where no torque is being added to the system. In this problem, there are no rotational forces acting on the satellite, so angular momentum is conserved. </p>
<p>Mathematically, ang. momentum = moment of inertia x angular velocity. Moment of inertia increases as the radius of rotation increases, while angular velocity increased as the radius of rotation decreases. They have an inverse relationship, so their product will always be equal.</p>
<p>I dont know if Im doing something wrong, but for me the answer to the question of the guitar string was that all values changed. Since the frequency changes, then wavelength must change, too, since the speed of sound is constant in the same medium. The tension, obviously, changes as well. So I think I, II and III were all true.</p>
<p>Ive just remembered other question, which was also a I, II, III - question. It asked about what values you should know to determine the internal heat of a material. One choice was density, the other specific heat and the other was mass. My answer was II and III, since density is not needed to calculate this. Any objection?</p>
<p>You are right about the internal heat.</p>
<p>You are wrong about the guitar string problem, though. The velocity of sound waves may be constant, but we’re not talking about the properties of a sound wave; we’re talking about the standing wave on the guitar string itself. Since the velocity of a wave on a string is dependent on tension, the wavelength of the string wave stays constant. Even as you tighten it. And the question wanted to know which components did not change.</p>
<p>^^I agree with that one about the internal heat</p>
<p>And thanks PioneerJones for the explanation!</p>
<p>^I believe PioneerJones is correct about the guitar string one</p>
<p>I’m glad I skipped the guitar one.</p>
<p>Ok, now I understand it completely. There was also one question of a Force vs. time graph (correct me if Im wrong), and they asked u about in which graph it was applied more impulse. It was this graph (with a triangle and a rectangle on the bottom):
y
l
l.
I….
I<strong><em>l</em></strong> x</p>
<p>If I remember correctly the area was 10.
As for the other graph question where it was KE vs. time. First they asked u what magnitudes are constant in interval A. Answer: None.
When is velocity equal to zero?: When the function of the graph touches the x-axis.(I think in the end of interval A)
And, when is velocity constant?: When the function is parallel to the x-axis, isnt it?? Please help!
There was also another question about an electron on a magnetic field. They first asked u in which graph would the magnetic force be zero. I believe it was when the velocity vector and the magnetic field lines were parallel. And then they asked in which graph would the magnetic force be pointing upwards. Im not sure though.
Moreover, the question of the particles: Proton, electron, neutron, quark and photon consisted on 2 questions based on that list of particles. Does anyone remember what the other question was? I think I put as an answer photon or quark, but I remember it very vaguely.</p>
<p>yeah on the KE graph, when the line is parallel to the x axis, nothing is changing so velocity would be constant</p>
<p>for the magnetic field one, the magnetic force points up in the one where the electron is entering from the left into a field with magnetic field lines pointing out of the page (dots instead of x’s)</p>
<p>and for the subatomic particles one:
which one has the smallest nonzero mass - electron
three of these make up something in the nucleas - quarks, 3 quarks make a proton</p>
<p>
</p>
<p>If the magnetic field lines were pointing out of the page, there is no way the magnetic force points out of the page</p>
<p>the question was asking for the force point up the page, not out of the page</p>