AP Physics 1 Question 56: Answer and Explanation
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6. A bubble in a glass of water releases from rest at the bottom of the glass and rises at acceleration a to the surface in t seconds. How much farther does the bubble travel in its last second than in its first second?
- A. at
- B. (t - 1)a
- C. (t + 1)a
- D. at
Correct Answer: B
B The distance travelled in the first second can be found using the Big Five,
dfirst = v0tfirst +
Using tfirst = 1 s and v0 = 0 m/s since the bubble starts at rest, the equation becomes
The distance traveled in the last second can be found using another Big Five equation.
Using tlast = 1 s and vfinal = v0 + attotal = attotal, the equation becomes
dlast = attotal – a
The question is asking for the difference in the distance, so
dlast – dfirst = attotal – a – a = attotal – a = (t – 1)a