Answer
The answer is below.
Work Step by Step
Each of the graphs in the book have a horizontal line on them, which represents the total energy. The roller coaster can never go above these peaks, for the mechanical energy is said to be conserved. In graph a, the horizontal line is above the whole curve, so the roller coaster goes from point a to point d. In diagram b, the horizontal line intersects the graph at about point c. Thus, once it gets to point c, the roller coaster will go back and forth between point c and the initial point where the horizontal line intersects the curve. In diagram c, the horizontal line intersects the graph at about point b. Thus, once it gets to point b, the roller coaster will go back and forth between point b and the initial point where the horizontal line intersects the curve.
