Topic 1.3 Alternate Lab: Walk the Graph

Reading a position-time graph is one skill. Producing the exact motion that graph describes is a different, harder skill — and it's exactly what real AP free-response questions ask for when they hand you a graph and ask you to describe, or reproduce, the motion behind it.

This lab flips the usual direction. Instead of walking first and graphing what happened after, you get the graph first, and you have to predict — before you move a single step — what kind of walking would actually produce it. A flat stretch means standing still. A steep upward slope means walking away quickly. A slope that turns negative means turning around and walking back toward the start. The real test comes with graphs that combine several of these in one shape — away, then stop, then back — because mid-motion changes are much harder to execute precisely than one steady stretch of walking.

The setup is deliberately equipment-free. A motion detector graphing your position live is nice if it's available, but a stopwatch, a hallway marked off in meter intervals, and a partner calling out time checks work just as well. Either way, the goal is the same: predict your walking pattern in words first, walk it, compare the result to the target graph, and adjust if it doesn't match.

Videos

This is a hands-on lab day — no video assigned. A quick 2-3 minute re-watch of the "walking" demonstration portion of the Topic 1.3, Session 1 video is a useful refresher before starting.

Try It Yourself

This was a lab day, so instead of a written problem set, here are the same questions the class worked through with their own walking data:

1. Which target graph was hardest to match, and why? (Most groups find that a graph requiring a stop or a direction change is harder to execute precisely than one steady stretch of motion.)
2. For the constant-velocity graphs, how did walking speed relate to the steepness of the line?
3. What made your walked graph not perfectly match the target — reaction time, an uneven pace, detector noise, or something else?
4. Design your own "mystery graph" — flat, sloped, or some combination — and describe in words exactly how someone would need to walk to match it, without showing them the graph first.