Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Problem 2.43
[3.0 points.] A brick is thrown and released vertically upward with an initial speed of 2.00 m/s from the top ledge of a building, 12.0 m above ground level. The brick reaches its highest height, then moves downwards to strike the ground. Take upwards to be the positive vertical direction. Which is the graph of v_y(t) for the brick? Clearly circle your choice below.?
Correct answer: (B)
With positive +y direction being upwards, the acceleration of an object in free fall is a_y = -9.80 m/s^2, which must be the slope of the v_y(t) graph. Graph (E) is correct except that the positive +y direction is downwards. Graph (C), the most common error, resembles in a crude manner the parabolic y(t) graph of an object ascending, and then descending down below its initial position above the ground.
Student responses
Sections 0906, 0907
(A) : 1 student
(B) : 5 students
(C) : 23 students
(D) : 1 student
(E) : 9 students
(F) : 12 students
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