2018, Question 3 · Long free-response · 12 points · about 25 minutes
Spinning disk slowed by axle friction
Sketch angular velocity and angular acceleration for a disk slowed by constant friction, derive its rotational inertia, redo the sketches when oil reduces the friction, and pick a plausible torque model.
This exam had five free-response questions in 90 minutes: Questions 1, 4 and 5 were short questions worth 7 points each with about 13 minutes suggested, and Questions 2 and 3 were long questions worth 12 points each with about 25 minutes suggested. The current exam has 4 free-response questions in 95 minutes. The skills these questions practice still count.
Lessons this question draws on
1 Read the question
The question is College Board's, from the 2018 exam. It starts on page 8 of the PDF. College Board no longer posts this exam, so it opens from the copy of College Board's PDF that the Internet Archive saved on April 14, 2026.
2 Write your answer
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3 Score it
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Scoring guidelines (PDF, page 11) What the exam readers saw (Chief Reader report)
Question, scoring guidelines and Chief Reader report: College Board, from the Internet Archive. The title and summary are ours.