<p>ok, i thought 5x10^8 was there to trick ppl, lol. </p>
<p>and there was a wire with current I passing through, particle was moving toward wire with velocity v. which does not change the magnitude of B? </p>
<p>i eliminated it down to velocity of particle and direction of current.</p>
<p>The direction of current is irrelevant as it says the magnitude of the force NOT the direction of the force switching the direction has no effect on the magnitude.</p>
<p>The compasses: Was it a wire perp. to the page?</p>
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<p>Thought it was since the compass directions were arranged in a circle, which would fit the field lines from a wire [right-hand rule].</p>
<p>What was the half-life one with the mummy? I put 5x10^-3 but wasn’t sure at all, we never learned this in class and what I learned outside of it was quite basic.</p>
<p>yea it was a wire. i was expecting cb to split the answer into two answers, one wire with current into page and one out of page. but w/e, it makes it easier for us ^^</p>
<p>Yeah, the fact that all the other possibilities for that question had two options kind of threw me off. Still got it though.</p>
<p>For the efficiency, the it’s not simply low temperature over high temperature, as the goal of the engine is not to put all of its energy right from the high temp area into the low temp area-what would that accomplish. Instead, it wants to convert that energy to work. The question asks for the ideal efficiency of the engine, so carnot efficiency, which is equal to 1-Tl/Th (Tl=low temp Th=high temp), so 1-75%=25%.</p>
<p>Dang, that was the one formula in PR I didn’t bother to memorize x.x</p>
<p>The other question with that diagram was 100J, right?</p>
<p>Yeah.
(10char)</p>
<p>The half life one had to have been 5 x 10^3. All the others would either have decayed too far or not decayed at all for something about 5000 years old.</p>
<p>Any guesses on the curve or on the problems I posted on the last page?</p>
<p>curve im guessing is around -15 for 800</p>
<p>^wow, that’s pretty nice. is that what it generally is?</p>
<p>-15 is pretty typical, at least according to the test in the official guide.</p>
<p>For the question about the interference of the two sources of waves (wavelength was .5m I think), was the answer greater than all the surrounding points, or greater than some of the surrounding points? The wording of that one confused me.</p>
<p>yes it was brighter than all because they were 1 wavelength apart</p>
<p>so what was the halflife thing??</p>
<p>Good that was what I put. I was just confused by the terminology because there would also be other points of equal amplitude spaced .5 meters apart.</p>
<p>I also put the one with I believe 5 x 10^-3. This would give the most accurate date, as decay would happen much more quickly than the others. For some of the other answers it could place the age in a range of thousands of years.</p>
<p>I think that’s right at least.</p>
<p>for the half life one i thoguht the question was asking which would be the most accurate so i piccked tthe smallest one ^-3</p>
<p>the smaller the half lifes are the more accurate you could decide time period. (think of it as a number between 1-100 or a number between 20-80, which is more accurate).
I hope i was right, but its not like you’re goign to run out of atoms because the half life is so small, there are billions or whatever.</p>
<p>EDIT: Guy above me said it first :</p>
<p>I left 14 blank but I was REALLY careful and didnt take any chances, I hope.</p>
<p>half life was 5x10 ^3
this is because it would give the most accurate reading. You would have exactly .5 of the sample left. If it was 5x10^-3 then you would have an infintismally small mass that would be hard to calculate.</p>