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</p>
<p>All I remember from that question was the “no work done” choice was false.</p>
<p>^^^^^yes I put 50 C as the answer, my reasoning was 100 g + 200 g = 300 g total and the 100g was at 30 C and the 200 was at 60 C. So, 100/300 or (1/3)(30)=10 and 200/300 = 2/3, so (2/3)(60)=40, and 40 + 10 = 50 C.</p>
<p>I have no idea if that was the correct way to solve the problem; it seemed logical</p>
<p>Compiled Answers
-Universe expansion: red shift + something else, I & II
-Oil drop: calculate electron charge
-Ice cube -50 C to 150 C:
… _<em>/
… /
.</em>/
/
-Initial velocity 30 m/s, v and a at apex: 0 m/s, -10 m/s^2
-Initial velocity 30 m/s, v and a final: 30 m/s, -10 m/s^2
-X and Y collision: need to know masses (was this the same as ratio of the masses?)
-Insulator/conductor: glass and aluminum
-Starting a fire: converging lens
-Cop car moving: fA < f0, fB > f0
-People moving: fA > f0, fB < f0
-Heavy ball versus lighter ball: I put ratio of V to SA was smaller in the larger ball
-Lightest particle: electron (I just googled this)
-Magnification of diameter of coin: 6 (choice A)
-Ball going east, force applied to it: went east, curved, and carried on this way diagonally southwest
-Why doesn’t moon crash into earth: Constant gravitational pull, but the velocity keeps it from crashing
-Electroscope, what was the rod’s charge: negative
-Which one didn’t have a 1/r^2 graph: potential energy of charge
-Maximize magnetic force: I, II, and III (velocity of particle, charge of particle and magnitude of magnetic field)
-Moon and earth gravity, change in mass: no change (arghhhh I got tricked T.T)
-Moon and earth gravity, change in force: 160 N
-20 ohm and 40 ohm resistor: h/2
-Changing induced current: I, II, and III (area, resistance, rate of change of field)
-Charge and circle, change in potential: I and II
-Charge and circle, MAX change in potential: I
-Charge and circle, no work: III
-Two samples: 50 degrees C
-Buzzing noise: ???
-P/V graph for heat engine: ???</p>
<p>oh i think i remember now
I internal energy the same for 1 and 3
II no work done for 2 and 4
III initial and final temperature is the same</p>
<p>i dont remember at all what i put for this :(</p>
<p>btw, everything in the compiled list is what i got :)</p>
<p>^(mcT)one subtance = (mcT)second subs</p>
<p>
</p>
<p>I did it as a weighted average and got 50 also.</p>
<p>[(100)(30)+(200)(60)] / 300</p>
<p>The correct way to solve it is 100c(t-30) + 200c(t-60) = 0, where c is the specific heat of water and t is temperature.</p>
<p>
</p>
<p>II,III are correct</p>
<p>^Do you rmemeber if I, II, and III was a choice for the heat engine one?</p>
<p>i’m pretty sure ‘I’ was wrong
i put II and III</p>
<p>^Lol idk. I’m just trying to figure out if I guessed or not.</p>
<p>
</p>
<p>Oh ok</p>
<p>Does anyone remember the one about the normal force and the cart like goes in a circle and there’s 5 points, A,B,C,D, or E? A and E were the bottom and top of the circle, respectively. I left this one blank lol</p>
<p>^Normal force is greatest when cart is on bottom</p>
<p>Pendulum question: when is acceleration greatest? I put when it’s at the bottom</p>
<p>@schoolisfun: i put the one that was at the very top of the circle.</p>
<p>The normal force is strongest at the bottom of the circle. Point A, I think.</p>
<p>What about the scientist one - where they asked for the wrong match between the scientist and their contributions?</p>
<p>NOOO I put A originally too! Then i erased >.<</p>
<p>a for the normal force one
not sure about the scientist one, but i put galileo and heat energies (B i think)</p>
<p>@Opus - Galileo</p>
<p>Are you guys sure about the 20 ohm 40 ohm resistor question? A lot of people agreed with h/2, and i think that’s what I put. But someone earlier commented on it being 4h bc Heat = (I^2)(R)(t)–which is true, and I do remember going through that thought process.</p>
<p>@schoolisfun: I am not sure if it is A; it is simply what i put.
@opus: It was galileo; it did not do much with heat engines</p>