## 20170922

### Physics quiz question: comparing distances traveled

Physics 205A Quiz 2, fall semester 2017
Cuesta College, San Luis Obispo, CA The x(t) graph of a Physics 205A student walking along a straight line is shown at right. The student started at x = 0 at t = 0. The student walks the greatest distance during the time interval(s):
(A) 0 ≤ t ≤ 3 s.
(B) 3 s ≤ t ≤ 7 s.
(C) 7 s ≤ t ≤ 10 s.
(D) (There is a tie.)

Correct answer (highlight to unhide): (D)

The positions of the student at different times can be immediately read off of this position versus time graph.

At t = 0, the student is located at x = 0 (this is also given in the statement of the problem). At t = 3 s, the student is then located at x = –2 m, such that the student traveled 2 m (in the negative direction) during the 0 ≤ t ≤ 3 s time interval.

At t = 3 s, the student is located at x = –2 m. At t = 7 s, the student is then located at x = –1 m, such that the student traveled 1 m (in the positive direction) during the 3 s ≤ t ≤ 7 s time interval.

At t = 7 s, the student is located at x = –1 m. At t = 10 s, the student is then located at x = –3 m, such that the student traveled 2 m (in the negative direction) during the 7 s ≤ t ≤ 10 s time interval.

Since the student traveled 1 m during the 3 s ≤ t ≤ 7 s time interval, but traveled 2 m during both the 0 ≤ t ≤ 3 s and the 7 s ≤ t ≤ 10 s time intervals, the most correct response is (D).

Sections 70854, 70855
Exam code: quiz02BjRn
(A) : 1 student
(B) : 19 students
(C) : 3 students
(D) : 32 students

Success level: 58%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.74