Physics 205A, Spring Semester 2009
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Multiple-Choice Question 2.1
Students were asked the following clicker questions (Classroom Performance System, einstruction.com) in the middle of their learning cycle (after being asked about the acceleration while the ball is traveling downwards, and while traveling upwards):
A ball is thrown and released such that it initially travels upwards. While it is momentarily at its highest point, its acceleration is __________. (Up = +y direction; neglect air resistance ("free fall").)
(A) +9.80 m/s^2.
(B) 0 m/s^2.
(C) –9.80 m/s^2.
(D) (More than one of the above choices.)
(E) (None of the above choices.)
(F) (I'm lost, and don't know how to answer this.)
Sections 30880, 30881
(A) : 0 students
(B) : 30 students
(C) : 13 students
(D) : 0 students
(E) : 0 students
(F) : 0 students
Correct answer: (C)
A whole-class discussion on velocity versus time graphs for objects in free fall immediately followed the tallying of results. All v_y(t) graphs for free fall may have different initial v_i,y values, but would all have the same negative slopes, and thus acceleration values of -9.80 m/s^2.
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