If you drop an object from the top of a tower, how many feet will it fall in the first second?

This result is a classic calculation in introductory physics, and it all comes down to the constant acceleration of gravity. Here on Earth, gravity doesn't just pull objects downward; it causes their speed to increase by about 32 feet per second for every second they are in free fall. An object dropped from a standstill starts at zero speed, but after one full second, it will be traveling at a rate of 32 feet per second.

To find the distance it fell, we need its average speed during that first second. Since it started at 0 ft/s and ended at 32 ft/s, its average speed over that interval was 16 ft/s. Traveling at an average of 16 feet per second for one second means it covered a distance of 16 feet. The negative sign is a convention used by physicists to indicate the direction of movement is downward, as opposed to upward.

This principle, that all objects accelerate at the same rate regardless of mass, was famously demonstrated by Galileo Galilei. It was proven most dramatically during the Apollo 15 mission, when astronaut David Scott dropped a hammer and a feather on the Moon. With no air resistance to slow the feather down, both objects hit the lunar surface at the exact same moment. The -16 feet calculation is an ideal figure that ignores air resistance, but it's the foundational number for understanding motion under gravity.