SAT Subject Physics Practice Question 156: Answer and Explanation

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Question: 156

2. For an object traveling in a straight line, its velocity (v, in m/s) as a function of time (t, in s) is given by the following graph.

Which graph best illustrates the object’s acceleration?


Correct Answer: D


If the velocity vs. time graph has a corner, then the acceleration vs. time graph will be discontinuous (have a jump). As shown in the diagram, the first part of the velocity vs. time graph is a straight line with a positive slope. Thus, the corresponding acceleration graph should be a horizontal line above the axis. Next on the velocity vs. time graph there is a curvy part, decreasing but concave up (like the left half of a cup). The slope of that is negative to begin with and then becomes less negative as we approach the center of the cup. Thus a straight line on the acceleration vs. time graph–negative but getting less negative.

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