Physics 5A, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Conceptual Question 1.7 (extended)
Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the beginning of their learning cycle:
[0.3 participation points.] In general, what is the difference between an average and an instantaneous quantity?
(A) The amount of change that takes place.
(B) The amount of time for a change to take place.
(C) How fast the object is moving.
(D) The number of times that a change takes place in a given time interval.
(E) (I'm lost, and don't know how to answer this.)
Sections 4987, 4988
(A) : 7 students
(B) : 14 students
(C) : 1 student
(D) : 17 students
(E) : 3 students
Correct answer: (B)
For example, average velocity is defined as the displacement of an object divided by a finite time interval, whereas instantaneous velocity is defined as the vanishingly small ("infinitesimal") displacement of an object divided by a vanishingly small ("infinitesimal") time interval. Students seemed to confuse the semantics of the term "average" with the sampling of many results, as opposed to "instantaneous" being only one event.
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