2015 AP Physics 1 free response 3d

All right, Part D explains how any correct aspects of the student's reasoning identified in Part B are expressed by your mathematical relationships in Part C. It also explains how your relationships in Part C correct any incorrect aspects of the student's reasoning identified in Part B. It's a bit of a mouthful, but they're just saying, "Hey, kind of connect the dots between Part C and the two parts of Part B."

Refer to the relationships you wrote in Part C, not just the final answer you obtain by manipulating those relationships. So, let me write it down here.

So, Part C shows us that doubling compression does result in more potential energy. Doubling compression does result in more energy, and you could clarify that this is potential and kinetic at different points in time. We could even draw a line to it. We see that right over here—that is that line—and then that line right over there shows that.

So I could draw a bit of an arrow to it. They want us to reference some of what we saw before and just to make it clear, I can put in parentheses that U2 is equal to 4U1 and that K2 is equal to 4K1. However, since the kinetic energy is four times greater and you have the same force of friction, the distance is going to be four times as long.

The stopping distance is going to be four times as much; it's going to be four times as long. Even when we point out the correct parts, Part C shows us that doubling the compression does result in more energy. I could add "and more stopping distance."

Let me do it there: "and more stopping distance." Whoops! And more stopping distance; the stopping distance that arrow is easier to draw. However, since the kinetic energy is four times greater and you have the same force of friction, the stopping distance is going to be four times as long.

We saw that as well over there. So we’re saying, "Hey, look, the student was right that more compression is more energy, more stopping distance." However, it's going to be four times as long, the stopping distance—not two times as far. And there you go.