What Is Millimeter per Second (mm/s)?
Millimeter per second is a unit used to measure speed. It shows how many millimeters an object moves in one second. This unit is helpful when things move slowly or when we need very fine measurements, such as in science labs, tiny machines, or slow moving liquids.
Definition
One millimeter per second means that an object travels a distance of one millimeter during one second of time.
So if something moves at 5 mm/s, it goes 5 millimeters every second.
In math form:
speed in mm/s = distance in millimeters ÷ time in seconds
History / Origin
The unit millimeter per second comes from two parts of the metric system:
- Millimeter is a very small length unit. It is one thousandth of a meter. The meter became the basic length unit in the metric system in the late 1700s in France.
- Second is the basic time unit in the International System of Units. It was first linked to the day and later defined more exactly using atomic clocks.
When people needed to measure very slow speeds with high detail, they combined these two units to make millimeter per second. Today it is used in science, engineering, and medicine when meter per second would be too big and not precise enough.
Symbol & Abbreviation
The usual symbol for millimeter per second is:
- mm/s
Other ways you might see it written are:
- mm s⁻¹ in scientific writing
- mm sec⁻¹ or mm per sec in older or informal texts
All of these mean the same thing, but mm/s is the most common form in science and engineering.
Current Use Around the World
Millimeter per second is used worldwide, especially in places that follow the metric system. Some common uses are:
- Science and research: to measure slow flows of liquids or gases, like in chemistry or physics experiments.
- Engineering: to describe the speed of machine parts that move very slowly or with tiny steps, such as in precision robots, 3D printers, or CNC machines.
- Medicine: to show how fast blood flows in very small blood vessels in some tests.
- Geology and earth science: to express very slow movements, like the creeping of soil or ice.
For everyday things like cars, bikes, or running, people usually use units like kilometer per hour or meter per second instead.
Example Conversions
To work with millimeter per second, it helps to know how to change it to other speed units.
1. Millimeter per second to meter per second
- 1 meter = 1000 millimeters
- So, 1000 mm/s = 1 m/s
- To convert mm/s to m/s, divide by 1000.
Examples:
- 10 mm/s = 10 ÷ 1000 = 0.01 m/s
- 250 mm/s = 250 ÷ 1000 = 0.25 m/s
2. Millimeter per second to centimeter per second
- 1 centimeter = 10 millimeters
- So, 10 mm/s = 1 cm/s
- To convert mm/s to cm/s, divide by 10.
Examples:
- 5 mm/s = 5 ÷ 10 = 0.5 cm/s
- 60 mm/s = 60 ÷ 10 = 6 cm/s
3. Millimeter per second to kilometer per hour
- 1 m/s = 3.6 km/h
- First change mm/s to m/s, then m/s to km/h.
Example:
- 500 mm/s = 500 ÷ 1000 = 0.5 m/s
- 0.5 m/s × 3.6 = 1.8 km/h
- So, 500 mm/s = 1.8 km/h
4. Millimeter per second to inch per second
- 1 inch is about 25.4 millimeters
- To change mm/s to inch per second, divide by 25.4.
Example:
- 25.4 mm/s ÷ 25.4 ≈ 1 in/s
Related Units
Other speed units that are closely related to millimeter per second include:
- Meter per second (m/s) main SI speed unit, used in science and physics.
- Centimeter per second (cm/s) another small speed unit, 1 cm/s = 10 mm/s.
- Kilometer per hour (km/h) common for cars and road speeds, 1 m/s = 3.6 km/h.
- Inch per second (in/s) used in some countries that use inches.
- Foot per second (ft/s) another non metric speed unit, bigger than in/s.
All of these measure how fast something moves. They just use different length units and sometimes different time units.
FAQs
Q: What does millimeter per second measure?
A: It measures speed. It tells you how many millimeters an object moves in one second.
Q: When is mm/s better than m/s?
A: Use mm/s when things move slowly or when you need very fine detail, such as in lab tests, small machines, or tiny fluid flows.
Q: Is mm/s part of the SI system?
A: Yes. It is made from two SI base units, meter for length and second for time. Millimeter is a smaller form of the meter.
Q: How do I change mm/s to m/s quickly?
A: Divide the number by 1000. For example, 300 mm/s becomes 0.3 m/s.
Q: How fast is 1 mm/s in everyday life?
A: 1 mm/s is very slow. At that speed, it would take 1 second to move the thickness of a small coin and more than 16 minutes to move 1 meter.
Q: Why do some books write mm s⁻¹ instead of mm/s?
A: Both forms are correct. The s⁻¹ style is used more often in advanced science writing, but it means the same thing as per second.
