When a child stirs cornstarch into water, the mixture turns solid under a sudden punch but liquid under a slow stir — the same jamming physics that engineers now study for body armor, even though the armor itself is built from something else entirely

A kitchen physics trick—where cornstarch slurry hardens under impact then flows again—is teaching engineers how to stop bullets and shrapnel without traditional rigid armor. The post When a child stirs cornstarch into water, the mixture turns solid under a su…