What to do when a wheeled suitcase hits a bump in the road and starts to wobble? Walk a little faster. Yes, this is a question scientists have recently looked into, and they've got a couple pieces of advice for travelers. “If it’s not wobbling, it’s better to walk slower, but if it starts then it’s bad to slow down,” says Sylvain Courrech du Pont of Paris Diderot University. It all started when he assigned an experiment on the physics question to an undergrad class, only to learn that no previous research on it seemed to exist. So he and his colleagues took it upon themselves, using tiny model suitcases on a treadmill and theoretical calculations to sort out why the wobble and how to correct it, reports New Scientist.
If the disruption to the wheels is small enough, it'll self-correct quickly. If it's large enough, it'll rock harder until it falls over. And right in the middle, there's actually a sweet spot, they report in the Proceedings of the Royal Society A, where it could theoretically wobble forever, though uneven surfaces and gaits make this highly unlikely in the real world. In the scenario where the disruption is large enough to fully topple the suitcase, the best way to prevent this is to walk faster. Holding the the suitcase handle lower also seems to help, though Phys.org notes that doing both simultaneously "would require some degree of athleticism." The researchers mention speed skaters in the study: The faster and lower they move, the more stable they become. (This man likely knows all about suitcases now.)