Cuesta College, San Luis Obispo, CA
Cf. Knight, Five Easy Lessons: Strategies for Successful Physics Teaching, p. 85
Students were asked the following clicker questions (Classroom Performance System, einstruction.com) in the middle of their learning cycle:
Consider the x(t) graph of two objects moving along a straight line for t = 0 to t = 8 s, as shown at right. Do object 1 and object 2 have the same speed? (A) Yes, at t = 2 s.
(B) Yes, at t = 7 s.
(C) Yes, sometime between t = 2 s and 7 s.
(D) (More than one of the above choices.)
(E) No.
(F) (I'm lost, and don't know how to answer this.)
Sections 30880, 30881
(A) : 0 students
(B) : 0 students
(C) : 27 students
(D) : 0 students
(E) : 15 students
(F) : 0 students
This question was asked again after displaying the tallied results with the lack of consensus, with the following results. No comments were made by the instructor, in order to see if students were going to be able to discuss and determine the correct answer among themselves.
Sections 30880, 30881
(A) : 0 students
(B) : 0 students
(C) : 36 students
(D) : 0 students
(E) : 6 students
(F) : 0 students
Correct answer: (C)
The tangent slope of a position versus time graph is the (instantaneous) velocity. Since object 2 has a tangent slope that is identical to the slope of object 1, then they have the same velocity, and thus the same speed between t = 2 s and 7 s.
Pre- to post- peer-interaction gains:
pre-interaction correct = 64%
post-interaction correct = 86%
Hake, or normalized gain
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