The Human Element

1The Law of Attraction: The Battle between Fuel and Friction

When a bullet is fired from a gun, it leaves the barrel moving 1,300 feet per second, breaking the sound barrier. If shot at the ideal trajectory (45 degrees), it can travel for nearly two miles. But a bullet isn't just powerful. It's equally precise. In a steady hand, a bullet will strike its target with pinpoint accuracy, time and again. What enables such a technologically simple device to achieve such extraordinary power and precision?

Most people's answer is gunpowder.

When the trigger on a gun is pulled, a firing pin strikes the bullet, causing the gunpowder inside the bullet to burn. The burning gunpowder produces gas that rapidly expands, creating enormous pressure inside the barrel of the gun. The only way for the gas to escape is to push the bullet out through the end of the barrel.

A bullet needs gunpowder to fly. But gunpowder alone doesn't enable a bullet to achieve such incredible distance, speed, and accuracy. When an object takes flight, be it a bullet, an airplane, or a pitcher's fastball, two opposing forces are at play. There are propelling forces that thrust the object forward (gunpowder, a jet engine, or a pitcher's arm). And there are constraining forces (gravity and wind resistance) that operate against forward progress.

Gunpowder isn't the wrong answer to the question, What makes a bullet fly? It's just woefully incomplete. Gunpowder explains why a bullet leaves the barrel with such tremendous ...