AP · AP 1 · multiple choice
AP Physics 1: Algebra-Based · Question 5
AP Physics 1: Algebra-Based · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- demanding
- Marks
- 1
- Topics
- 2
- Answer
- Complete
A solid disk and a thin hoop have the same mass and the same radius. Both are released from rest at the top of the same incline and roll down without slipping. Which reaches the bottom first?
- A
the disk, because a smaller fraction of its energy goes into rotation
- B
the hoop, because its mass is farther from the axis
- C
neither — they arrive together, because they have the same mass
- D
neither — they arrive together, because gravity acts equally on both
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Answer and reasoning
Predict from the governing principle before looking for a matching option. Then reject alternatives by checking direction, units, limiting behaviour or the physical meaning of each statement.
- 1
The correct choice is A: the disk, because a smaller fraction of its energy goes into rotation
- 2
C and D are the answers of a candidate applying the free-fall result, where mass genuinely does cancel. It does cancel here too — but the rotational inertia does not, and the hoop's larger I/MR² leaves less of the released energy available as translational kinetic energy.
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