The road running past the school gym curves sharply just before it reaches the gym entrance. Because of the curve, a driver rounding it has no view of the road past the curve until they've come fully around it. The district wants to add a marked crosswalk somewhere on the straight stretch between the end of the curve and the gym entrance, so students can cross safely to reach the gym from student parking.
The district has asked you — acting as a student engineering consultant — to recommend exactly where the crosswalk should go and what speed limit should be posted on that stretch of road, and to justify both with physics.
Some of this is a fixed fact about the road. Some of it is a range you'll need to pick a value from and justify. Know which is which before you start calculating.
Use this tool to test speed limit and assumption combinations before you commit to a final recommendation. Try the worst-case combination first — it's the strongest test of whether your choice actually holds up.
Test a speed limit against your chosen assumptions. Stopping distance = reaction distance (v × reaction time) + braking distance (v² / 2a). Adjust the sliders to match the assumptions you're defending in your memo.
Try the worst-case combination (highest speed, longest reaction time, wet pavement) and see how much distance it demands — that comparison is the heart of your memo's argument.
| Criteria | Exemplary | Proficient | Developing | Incomplete |
|---|---|---|---|---|
| Physics Reasoning | Correctly combines reaction distance and braking distance; equation choices are justified by the missing-variable strategy. | Correct calculations with minor gaps in justification. | Major calculation errors, or reaction and braking distance are conflated or missing one piece. | No clear stopping-distance calculation shown. |
| Use of Given Data | Clearly distinguishes fixed facts from assumptions; chosen values are explicitly justified. | Uses appropriate values but justification is thin. | Uses given data but doesn't distinguish assumption from fact. | Given data ignored or misused. |
| Recommendation | Specific crosswalk distance and speed limit given, and both satisfy every constraint with a stated, reasonable margin. | Specific recommendation given; satisfies constraints with a margin, though margin reasoning is light. | Recommendation given but violates a constraint, or margin is unaddressed. | No specific, numeric recommendation given. |
| Defense & Safety Margin | Explicitly addresses worst-case conditions (reaction time, pavement) and explains why the margin covers them. | Addresses at least one worst-case factor. | Mentions safety margin without connecting it to a specific risk factor. | No safety margin discussed. |
| Communication | One page, professional tone, includes a clear supporting graph/chart, fully readable by a non-physics audience. | Clear and mostly jargon-free; graph present but could be clearer. | Difficult to follow, missing a graph, or exceeds one page. | Memo format not followed, or missing required elements. |