Rigid-body dynamics · Research Worlds
WHY TURN BACK?
Why does this spinning toy turn back without another push?
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Watch the 90-second visual story ↗What will you explore?
Kondo and Nakanishi, 2017
A contact torque can reverse spin as energy moves into rocking.
How does it work?
Watch a 90-second cinematic explanation, or explore a story that pauses so you can change its central mechanism. Inspect the source evidence, compare outcomes and resume the narration. This free Lesson Worlds adaptation needs no account or download; younger learners may want help from a parent or teacher.
Inside the cinematic story
WHY TURN BACK?
WHY TURN BACK?
A hidden mismatch
A hidden mismatch
Spin becomes rocking
Spin becomes rocking
Align the axes
Align the axes
Take control: What happens without the mismatch? Misaligned axes · Aligned axes
Two directions, different times
Two directions, different times
Take control: Do both directions take the same time? Quick reversal direction · Slow reversal direction
Where the model ends
Where the model ends
Discuss the evidence
Before starting, explain what you think this claim means: A contact torque can reverse spin as energy moves into rocking. After exploring, choose one stage above and describe what its model helps you see. Separate what you observed in the adaptation from what the original researchers measured.
Read the original publication for its methods, evidence and limitations. Ask which part of the explanation the interactive model leaves out, and what additional evidence you would need to test the claim yourself.
Original teaching reconstruction of Kondo and Nakanishi (2017), using the averaged small-motion equations 47–50. No-slip contact and no dissipation are assumed. Screen time, rocking amplitude and geometry are enlarged illustrations, not experimental footage or calibrated predictions. The full rigid-body solver and its fast-spin chaos are not reproduced. Aligning the axes is an ideal model comparison. Real friction can hide the slower reversal.
Original research
Rattleback dynamics and its reversal time of rotation
Yoichiro Kondo and Hiizu Nakanishi · Physical Review E 95, 062207 (2017) · 2017
Educational adaptation by Lesson Worlds. Not affiliated with the authors, Kyushu University or the American Physical Society. The original publication may have its own access terms.