<p>how about this question
the death star is moving towards a planet at a speed of 0.5c, it then fires an ion beam at 0.3c. assuming the planet is stationary, what is the observed speed of the beam from the planet’s view?</p>
<p>edit:how accurate are the pr test? is a 65 raw score good enough?</p>
<p>^^
if my interpretation of this problem is correct…(sorry, don’t have a picture)
Fg-Ft=Ft
so Ft=mg/2=ma
so a=g/2=5</p>
<p>@ Meteman, so as the entropy increases in a system, the temperature does not change?</p>
<p>^^ Why are there two tensions?</p>
<p>^^^ is the answer 16c/23 ?</p>
<p>@ bornsoccer and meteman, thank you.</p>
<p>Yes because when phase changes occur as heat is added to a system the phase it gets converted to has more entropy.</p>
<p>Miamirulz29, because the force of gravity is only affecting one block, but has to move two blocks of the same mass, or has to move double the mass. So the F=2mx, x has to be 1/2a for it to workout. 1/2a is 5m/s^2</p>
<p>ok thanks.</p>
<p>A worker hits a metal pipe with a hammer . The ratio of the intensity of loudness as heard by people standing 100 meters away from the worker to the intensity as heard by people standing 200 meters away from the worker is_______.</p>
<p>Answer is 4:1</p>
<p>Why?</p>
<p>Intensity is proportional to 1/r^2. So the people standing the ratio is 1/1^2: 1/2^2 which is 4 : 1. Don’t make the mistake of thinking it is 1 : 4 because the intensity is higher for the people that are closer.</p>
<p>Because the sound intensity dissipates at a ratio of pi*r^2.</p>
<p>how do you know if positive or negative work is done by moving a particle in an electric field/any thing in general? and are there significant digit questions on the test?</p>
<p>Thanks.</p>
<p>Just curious, what courses did you guys take to prepare for this? I took Physics C: Mech, so I’ve had to learn most of it on my own, and let me tell you, it is not going well…</p>
<p>I have taken physics b, so I knew almost everything except relativity and some of the nuclear physics.</p>
<p>@ Born4Soccer
Intuition, if you move a positive charge closer to a positive charger, YOU are pushing it and hence increasings its potential energy because as soon as you let go it will fly away.
If a positive charge gets pushed by a positive charge, the positive charge is doing work on it because it is pushing it away.</p>
<p>Today’s the big day, guys. Good luck :)</p>
<p>Dam that was hard haha, who agrees with me? And the stuff I studied barely showed up.</p>
<p>I didn’t really find it that hard.</p>
<p>That was somewhat hard. So few optics and no relativity. And lots of qualitative questions.</p>
<p>Also we can make a Consolidated List at 1:30 after the embargo is lifted right?</p>
<p>We’re not supposed to discuss the answers at all, but for some reason people just do it here.</p>
<p>I thought the test was actually pretty difficult…5 blank, maybe 10 winged?
I used barron’s btw, I thought those tests were easier.</p>
<p>oh well…</p>