A reasoning diagnostic for physics
See which physics idea is costing you points.
Take a 48-question multiple-choice diagnostic. Each wrong option was written to catch a specific misconception, so your report shows which ideas you keep getting wrong and links each one to a short explanation and a practice problem.
- For
- AP Physics students working toward F=ma and USAPhO
- What's here
- 48 questions, 66 Atlas entries, 57 practice problems on the ladders
Try a question from the diagnostic.
Pick any answer, right or wrong. You'll see what that choice usually says about a student's reasoning, and where the diagnostic would send you next.
A car rounds a flat curve at constant speed. The direction of the net force on the car is:
Nothing is scored or saved.
Waiting for an answer.
- 01 Answer —
- 02 Reasoning pattern the model behind the choice
- 03 Misconception code one of 12 trap families
- 04 Explanation · Error Atlas the entry that explains the trap
- 05 Repair · ladder rung the problem that rebuilds the idea
The full diagnostic does this for 48 questions, then ranks the misconceptions that come up most.
Start the 48-question diagnostic →What happens to a wrong answer.
The report, the Atlas links and the practice suggestions all come from the same answer key. Here is one wrong answer traced through each step.
- 01Answer patternWhich choice, on which item.
Q04 · chose B - 02Misconception codeEvery wrong option is linked to a misconception.
circular-direction - 03Diagnostic reportMisconceptions that come up repeatedly rank first.
ranked by recurrence - 04Error Atlas entryWhy the wrong idea felt right, and the correct one.
NL-05 - 05Recommended rungA problem that practises the missing idea.
R7 - 06Progress dataA held-out follow-up checks whether the trap recurs.
recurring / resolved
From the report to the next problem.
Your answers decide what you read next and which problem you try next, so your practice time goes to the ideas you actually miss.
Trap detected across items
Circular-motion direction error
- Q04A car rounds a flat curve at constant speed. The direction of the net force on the car is:
- Q05A ball on a string swings in a vertical circle of radius r. The minimum speed at the top for the string to stay taut satisfies:
- Q41A car rounds a banked curve without friction. Which force provides the necessary centripetal acceleration?
- Q42A ball swings on a string in a vertical circle. At the bottom of the loop, the tension is:
Each wrong choice is tallied by trap, so a pattern that recurs across items outranks a one-off slip.
NL-05 · one of 66 entries
Centripetal acceleration points inward
- 1
Tempting model. Drawing a “centrifugal” force outward on a body in circular motion.
- 2
Why it feels right. You feel flung outward in a turning car, so it seems a force pushes out.
- 3
Where it breaks. Your free-body diagram has a net outward arrow for something moving in a circle.
- 4
Correct model. The net force is centripetal — inward — supplying a = v²/r.
One new idea per rung
- R5Pulley constraintAP C
- R6Two-block system: choosing the systemAP C
- R7Circular motion: force directionF=ma
- R8Wedge/block constraintF=ma
- R9Non-inertial frame, introUSAPhO
R7 adds: Uniform circular motion has inward acceleration even at constant speed.
Where the numbers come from.
65 of 19,185 reached the verified cohort, and 45 have matched pre/post pairs. The bars are drawn to scale, and each says what it can and cannot support.
Full methodology →- 19,185prep users
Broad reach. Supports reach. It does not prove learning gain.
- 2,102diagnostics completed
Platform adoption. Supports product usage and diagnostic adoption.
- 65verified cohort
Research sample. Supports cohort-scale analysis.
- 45paired pre/post
Learning evidence. The layer used for learning-impact claims. Pre/post evidence, not a controlled trial.
Does knowing which reasoning step broke help more than doing another practice set?
Baseline diagnostic, targeted ladder work, held-out follow-up, paired comparison. We will publish the results with the sample size next to every number.