• If you forgot to include friction, and just set the student’s force equal to ma and solved, you could still
get 2 out of 4 points.
• If you solved part (a) wrong but still got a reasonable answer, say 4.5 N for the force of friction, and
plugged that in correctly here, you would still get either 3 or 4 points in part (b)! Usually the rubrics
are designed not to penalize you twice for a wrong answer. So if you get part of a problem wrong, but
your answer is consistent with your previous work, you’ll usually get full or close to full credit.
• That said, if you had come up with a 1000 N force of friction, which is clearly unreasonable, you
probably will not get credit for a wrong but consistent answer, unless you indicate the ridiculousness
of the situation. You’ll still get probably 2 points, though, for the correct application of principles!
• If you got the right answer using a shortcut—say, doing the calculation of the net force in your head—
you would not earn full credit but you would at least get the correct answer point. However, if you did
the calculation wrong in your head, then you would not get any credit—AP graders can read what’s
written on the test, but they’re not allowed to read your mind. Moral of the story: communicate with the
readers so you are sure to get all the partial credit you deserve.
• Notice how generous the partial credit is. You can easily get 2 or 3 points without getting the right
answer and 50–75% is in the 4–5 range when the AP test is scored!
You should also be aware of some things that will NOT get you partial credit:
• You will not get partial credit if you write multiple answers to a single question. If AP graders see that
you’ve written two answers, they will grade the one that’s wrong. In other words, you will lose points
if you write more than one answer to a question, even if one of the answers you write is correct.
• You will not get partial credit by including unnecessary information. There’s no way to get extra credit
on a question, and if you write something that’s wrong, you could lose points. Answer the question
fully, then stop.
The Tools You Can Use
You can use a calculator. Most calculators are acceptable—the acceptable calculator list is the same as
for the SAT or the AP calculus exam. The obvious forbidden calculators are those with a keyboard, cell
phones used as a calculator, or those calculators that make noise or print their answers onto paper.^1 You
also cannot share a calculator with anyone during the exam.
The real question, though, is whether a calculator will really help you. The short answer is “Yes”: you
will be asked questions on the exam that require you to do messy calculations (for example, you might
need to divide a number by π , or multiply something by the universal gravitation constant). The longer
answer, though, is “Yes, but it won’t help very much.” To see what we mean, look back at the hypothetical
grading rubric for part (b) of the example problem we discussed earlier. Two of the four possible points
are awarded for using the right equations, one point is awarded for finding the magnitude of a force using
basic arithmetic, and the last point is awarded for solving a relatively simple equation. So you would get
half-credit if you did no math at all, and you would get full credit just by doing some very elementary
math. You probably wouldn’t need to touch your calculator!
So definitely bring a calculator to the exam, but don’t expect that you’ll be punching away at it
constantly.