Solving the Riddle of Why Rolling Luggage Wobbles

Credit: Lee County Port Authority via Wikimedia Commons (Inside Science) --

Anyone who has ever had to rush from one airport gate to another may have experienced how much trouble a wobbly, rolling suitcase can cause, even while walking at modest speeds. Now scientists in France, experimenting with model suitcases on treadmills, reveal that the best solution for when such a suitcase comes close to overturning may not be to slow down, but to speed up. Such work exploring the physics of everyday life can shed light on the surprising behavior that can result when different kinds of motion come togethfer, the researchers said. Physicist Sylvain Courrech du Pont at Paris Diderot University began investigating the behavior of rolling suitcases to amuse his undergraduate students during experiments. But, the work also examined "a real scientific question" that few had studied, he said. Specifically, a rolling suitcase couples two kinds of motion -- when the wheels of the suitcase rotate, the bulk of the suitcase "translates," or moves in the same direction without rotating. The unstable way in which a rolling suitcase can behave represents an intersection of rotational and translational motion.