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Homework Help: AP Physics: Do you think I lost points for this on the AP exam?

  1. Aug 23, 2010 #1
    1. The problem statement, all variables and given/known data

    Well I was rather shocked when I got a four instead of a five and am wondering if I lost points for this.

    According to my teacher the way the college board states it is that student's must have a reasonable appreciation for significant figures and that is all. So during the test I kept two extra significant figures throughout the whole test just in case I needed to use that calculation later and then boxed in the answer with the appropriate amount of significant figures

    For example
    If question A said find a value and I was suppose to use two significant figures I would put

    A = B/C [about symbol] .2542 = .25
    then I would put a box around .25

    I did this because I've seen on some old scoring guidelines were you literally lost points if you used .25, even though it has the correct amount of significant figures, you have to carry a couple of extra digits over in feature calculations

    for example if I were asked right after this question on test to find D I would put

    D = A/E = .2541/E [about symbol] .5678 = .57
    then I would box in the .57

    it's stupid but the college board likes you to use your answer that you got in previous questions instead of just doing D = B/(CE) they literally put on some scoring guidelines "+1 for using answer found in previous part" or something like that were they literally expect you to put the numerical value instead of a formula incorporating the two or you can miss out on points

    This is why I wrote the version in the previous part with the extra significant figures because I have seen like I said before on scoring guidelines were if I used .25/E and the appropriate answer with correct significant figures came out to be .56 they would mark it wrong because carry a couple of extra significant extra figures would result in .57 and they would mark that correct

    now the college board hasn't really been consistent from year to year on scoring guidelines of how many extra significant figures you must carry over so I just used two as normally suggested when your asked to find one calculation and must use that calculation and might have to use that calculation in feature questions.

    Do you think I didn't get points or got marked wrong for using the method of writing out my solutions on the test this way? Let me know if you don't understand what I am asking here.
  2. jcsd
  3. Aug 23, 2010 #2
    You only get one point for the answer approximated as a real number. If you understood the material as you thought you did, you could've gotten a 5 without even calculating the final answer but showing the entire process that precedes it. There is a lot of room for error on the AP exam, and a 4 is fine if you want to use it for most colleges.
  4. Aug 23, 2010 #3
    College Board, in my experience with the last AP test, hasn't been very harsh with grading whatsoever concerning significant figures. I took AP Physics B as a sophomore in high school and have never had to use significant figures before (I hadn't taken chemistry yet), and always rounded to 2 decimal places if the requested estimation wasn't specified (I got a 5 without looking nearly as deep into the rounding)...I think your grade had more to do with your understanding of the content than with the way you presented it. Just my observations though..
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