The figure shown gives the position of a car moving in the x-direction as a function of time, x(t). Four times are marked by blue squares and labeled A - D. For which times is the acceleration of the car positive? Hints: 1. You can assume that the motion of this car can be described by a series of time intervals (4 actually) during which the acceleration is constant. 2. It might help to use this position graph to draw a graph of velocity vs. time. There are several graphs in the reading that compare the velocity, v(t), and the acceleration, a(t). X A B C D