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.
Millimeters per second (mm/s)
Millimeters per second (mm/s) is a unit of speed. One meter is equivalent to 1000 millimeters and this unit is the number of millimeters travelled in one second.