To penetrate armor, a projectile’s point concentrates force in a small area, creating a stress large enough that the armor fails. A species of jellyfish launches a pointed needle that can penetrate the hard shell of a crustacean. The rapid deceleration on impact creates a 32 μN force on the tip, which has a very small 15 nm radius. What is the resulting stress? How does this compare to the ultimate stress of steel?