CollegeBoard SAT Physics Study Guide PT1 Q12

CollegeBoard's Book

12) This question simply asks which situation shows that the object is switching its direction of motion. Many students might be tempted to select choice E off the bat, but with a closer look, the particle in choice E starts with a high velocity, slows down until rest, and then speeds back up. In order for the particle to change its direction of velocity, the velocity vs. time graph must pass the x-axis. This means either it will start with a positive velocity and have a negative velocity at some point, or it will start with a negative velocity and have a positive velocity at some point. Only choice D passes through the x-axis.

Answer: D