AP · AP C:M · multiple choice
AP Physics C: Mechanics · Question 1
AP Physics C: Mechanics · Original GioPhysics question with a detailed, mark-by-mark answer guide.
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multiple choice1 mark
A particle moves along the x-axis with acceleration a(t) = 6t, where a is in m/s² and t is in seconds. At t = 0 the particle is at rest at the origin. What is its position at t = 2.0 s?
- A
4.0 m
- B
8.0 m
- C
12 m
- D
24 m
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Answer overviewCorrect answer: B — 8.0 m
01
1 markAnswer and reasoning
How to approach it
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 B: 8.0 m
- 2
Integrating twice gives v = 3t² and x = t³, so x = 8.0 m at t = 2.0 s. D is the answer of a candidate who evaluates a at t = 2.0 s to get 12 m/s² and then applies x = ½at², which is only valid for constant acceleration — the whole point of the item is that this acceleration is not constant.
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