Feet per second (ft/s) is an imperial speed unit commonly used in ballistics, fluid dynamics, and engineering calculations within the United States. Projectile velocities, pipe flow rates, and conveyor belt speeds are often expressed in ft/s in American technical documentation. One foot per second equals exactly 0.3048 meters per second or about 0.6818 miles per hour.

Mach (Ma) is a dimensionless speed unit representing the ratio of an object's speed to the speed of sound in the surrounding medium. At sea level under standard conditions, Mach 1 equals approximately 343 meters per second or 1,235 kilometers per hour, though this varies with altitude and temperature. Supersonic aircraft travel above Mach 1, while hypersonic vehicles exceed Mach 5.