A particle is moving along the x-axis and its position-time graph is shown. Determine the sign of acceleration.

Explanation

By observing the s-t graph, we can determine the sign of acceleration . Recall if the graph is concase upwards, the slope is increasing , if it is concave downward, the slope is decreasing , and if the graph is straight line, the slope is constant.

OA : Slope is increasing, v is increasing and a is positive.
AB : Slope is constant, v is constant and a = 0.
BC : Slope is decreasing, v is decreasing and a is negative.
CD : Slope is increasing, v is increasing and a is positive.
DE : Slope is constant, v is constant and a = 0.