16 May 2012

2012 AP Physics B exam solutions -- my own attempt

Folks, The 2012 physics B exam is available now from the College Board.  Although it is an extremely difficult Physics B problem, I especially like #2 -- it's virtually identical to the first approach to the USIYPT problem called "astroblaster" that we did for the 2012 tournament in Oak Ridge, TN.  My student who presented that problem at the tournament had better have gotten that right.  :-)

Anyway, I spent the afternoon making up my own solutions.  No guarantee as to correctness.  

I can't post the solutions here due to a possible plague of lawyers.  But since the College Board copyright statement says their materials can be used for "face-to-face teaching purposes," I can allow teachers to access them.  The "pretty good physics -- secure" website is run by Gardner Friedlander, a Wisconsin teacher who's a veteran of many an AP reading.  If you're not already a member, follow the instructions on its front page to join.  Gardner will add you as quickly as he can.  

(If you're a student, beg your teacher to join tomorrow.)

And once you join, here's the link to my solutions on PGP-secure.  Have fun!  Please send corrections when you find my mistakes... I'll guarantee I got a 5, but not that I got a perfect score.  :-)


  1. Can you release your possible solution to me? I have a huge homework assignment due tomorrow and these problems need to be solved, I have no idea how to solve them!!!

    Please let me know if I can have them!

  2. Of course you can! $1 million, cash or wire transfer, and I'll throw in solutions to all your homework the rest of the year. When the money arrives, I'll release the file to you.


  3. What were your thoughts on the level of difficulty of the free response this year (relative to previous exams)?

  4. 5ci asks for the current through Y, not X. Check your solutions since it's not the total current anymore.

  5. Darren, you're right that I calculated through X.

    Anon, I'll first answer your question that I think the difficulty was dead-on normal overall. I thought that #2 was extremely tough, especially for a 10-point question. However, I thought that #7 was the easiest atomic/nuclear question in ages. Everything else was on target, so the overall difficulty was standard.

    Two caveats: (1) That's a first impression.

    More importantly, (2) IT DOESN'T MATTER to the scoring. If the free response section is harder than usual, then a lower total score will be necessary to earn each grade; similarly, an easy free response drives the scores for each grade up.

    I might sometime post a discussion of how AP score cutoffs are set.


  6. The second free response problem is interesting. I didn't the math and ended up with h>H. The astroblaster experiment may prove that my answer is correct.