I have heard that a penny dropped from a great height would kill someone if it hit them, but falling rain does not hurt when it hits you. Why not?
Ron Mileston, Wilmette
The Earth’s gravitation causes all objects falling in a vacuum to fall at a constantly accelerating rate. For every second that an object falls in a vacuum, its downward speed increases by 32 feet per second; after two seconds, at 64 feet per second; after three second, at 96 feet per second; etc. But raindrops fall through air, not through a vacuum. Although gravity is pulling the drops downward, drag increases as the fall speed increases, until it equals the gravitational force, when its speed becomes constant. For the largest, fastest raindrops, the fall speed is about 30 feet per second—too slow to hurt us.