Physics of murder, superball style

Indispensable wisdom from the XKCDverse: "After falling from seven stories, the mass of bouncy balls would be moving at about 20 meters per second.... If you wanted to be sure of killing someone, you'd need 3,000,000 of them—enough to fill a large room—to guarantee that the target would either be crushed to death by the impact or buried too deep to dig themselves out."