Miles per hour (mph, mi/h)
Miles per hour (mph or mi/h) is the number of miles covered in one hour. It is the unit for road speeds in the United States and the United Kingdom, and 1 mph is exactly 0.44704 meters per second.
Kilometers per second (km/s)
Kilometers per second (km/s) is a unit of speed that measures the number of kilometers traveled in one second. It is occasionally used in astronomy and astrophysics where large distances are involved.