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Question 10 of 36

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SAT Subject Test

Each option presents a graph. The horizontal axis is labeled t and the vertical axis is labeled v. The origin is labeled O.  The plot is a straight line starting at the origin and extending diagonally upward to the right.

A block is pulled along a horizontal surface with a constant horizontal force of magnitude F. The surface exerts a frictional force of constant magnitude f on the block. The graph of speed v as a function of time t for the block is shown above.

Which of the following shows the graph of acceleration a as a function of time t for the block?

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Each option presents a graph. The horizontal axis is labeled t and the vertical axis is labeled a. The origin is labeled O.  The graph shows a straight line starting at the origin and extending upward to the right.

Correct Answer: 
No

The plot shows a straight line parallel to the horizontal axis, starting at a point more than halfway up the vertical axis and extending to the right.

Correct Answer: 
Yes

The graph shows a concave up curve starting near the top of the vertical axis. It slopes down steeply to the right and then approximates a horizontal line near the horizontal axis.

Correct Answer: 
No

A concave up curve is shown starting at the origin. It curves up and to the right, at first with a shallow slope and then becoming gradually steeper.

Correct Answer: 
No

A concave down curve starts at the origin. It curves up and to the right, at first with a steep slope and then becoming gradually less steep.

Correct Answer: 
No

The correct answer is (B), a constant acceleration. At each instant the acceleration is the slope of the velocity graph. Since the velocity curve is a straight line that has constant slope, the acceleration is constant. Alternately, the description indicates that both the force pulling the block and the frictional force are constant. Acceleration is force divided by mass, so it also must be constant.

Question Difficulty: 
easy