Foot per second (ft/s)
The foot per second, symbol ft/s, is an imperial unit of speed representing how many feet an object travels in one second. It originated in English engineering and physics as a practical unit for measuring velocities on land and in laboratory settings. One ft/s equals 0.3048 meters per second. While less common in everyday applications compared to mph, it is still used in scientific experiments, ballistics, and technical specifications in the United States. The unit bridges imperial measurements with precise, time-based speed calculations.
Knot (kn)
The knot (kn) is a unit of speed based on nautical miles per hour, widely used in both maritime and aviation navigation. The term comes from an early method where sailors used a rope, known as a log line, with evenly spaced knots to gauge a ship’s speed. By counting the number of knots that passed overboard during a set period, they could estimate how fast the vessel was moving. One knot is defined as one nautical mile per hour, equivalent to roughly 1.852 kilometers per hour. Today, the knot is universally adopted for sea and air navigation, providing a consistent and reliable standard for measuring speed in global transportation.