Meter per Second
Symbol: m/sWorldwide
Was ist ein/eine Meter per Second (m/s)?
Formal Definition
The meter per second (symbol: m/s or m·s⁻¹) is the SI derived unit of speed and velocity. It is defined as the distance in meters traveled per second of time. Since both the meter and the second are SI base units — the meter defined by the speed of light and the second by the cesium-133 atomic transition — the meter per second inherits their precision and universality.
One meter per second equals 3.6 kilometers per hour, approximately 2.237 miles per hour, and approximately 1.944 knots. It is a moderate speed in human terms: a typical walking speed is 1.2-1.5 m/s, a brisk jog is 3-4 m/s, and the fastest human sprinters reach approximately 12 m/s.
Role in Physics
The meter per second is the natural unit of speed in all physical equations. Newton's laws, kinematic equations, fluid dynamics, wave propagation, and relativistic mechanics all use m/s as the fundamental speed unit. The speed of light — the universal speed limit — is defined as exactly 299,792,458 m/s, making the meter per second the unit in which nature's most fundamental speed constant is expressed.
Etymology
Component Units
The term "meter per second" is a compound unit formed from the meter (the SI base unit of length) and the second (the SI base unit of time). The word "meter" derives from the Greek "metron" (μέτρον, meaning "measure"), adopted into French as "mètre" during the creation of the metric system in the 1790s. The word "second" comes from the Latin "secunda pars minuta" ("second small part"), referring to the second division of the hour into sixty parts.
Adoption as SI Unit
The meter per second became the coherent SI unit of speed when the International System of Units was established in 1960. Unlike some derived units that receive special names (newton, pascal, joule), the unit of speed retains its compound name, reflecting its straightforward derivation from base units.
Precise Definition
SI Definition
The meter per second is defined as the speed at which an object covers a distance of one meter in one second. In SI notation: 1 m/s = 1 m ÷ 1 s. Since the meter is defined as the distance light travels in vacuum in 1/299,792,458 of a second, the meter per second is ultimately defined through the speed of light and the cesium-133 atomic clock.
Conversions
Exact conversions: 1 m/s = 3.6 km/h exactly. Approximate conversions: 1 m/s ≈ 2.23694 mph, 1 m/s ≈ 1.94384 knots, 1 m/s ≈ 3.28084 ft/s. In reverse: 1 km/h = 0.27778 m/s, 1 mph ≈ 0.44704 m/s, 1 knot ≈ 0.51444 m/s.
Vector vs. Scalar
In physics, speed (scalar) and velocity (vector) are both measured in m/s but carry different meanings. Speed measures how fast an object moves regardless of direction; velocity includes both magnitude and direction. A car traveling in a circle at a constant speed of 10 m/s has constant speed but continuously changing velocity because its direction changes.
Geschichte
Origins in the Metric System
The meter was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. The second had been defined since ancient times as 1/86,400 of a solar day. Together, these units naturally defined speed in meters per second. Early scientific measurements of speed — such as the speed of sound — were reported in various units (pieds per second, toises per second) until the metric system standardized measurement.
Speed of Light Measurement
The history of measuring the speed of light is intertwined with the meter per second. Ole Rømer made the first estimate in 1676 (approximately 220,000 km/s). Fizeau measured it at approximately 313,000 km/s in 1849. Michelson achieved 299,796 km/s in 1926. The modern defined value of exactly 299,792,458 m/s was adopted in 1983, simultaneously redefining the meter in terms of the speed of light.
Modern Scientific Use
Today, the meter per second is the universal unit of speed in scientific publications. While everyday life uses km/h or mph for vehicle speeds, and knots for marine and aviation, all scientific work — from particle physics to astrophysics — uses m/s. The Voyager 1 spacecraft travels at approximately 17,000 m/s relative to the Sun, and the Earth orbits the Sun at approximately 29,800 m/s.
Aktuelle Verwendung
Science and Engineering
The meter per second is used exclusively in scientific contexts. Wind speed in meteorological research is reported in m/s (though public forecasts may use km/h or mph). Flow velocities in fluid dynamics are calculated in m/s. Seismic wave speeds in geophysics are reported in km/s (thousands of m/s). Particle velocities in physics are expressed in m/s or as fractions of c (the speed of light in m/s).
Weather and Wind
The Beaufort scale, used internationally for wind classification, defines categories in m/s: calm (0-0.2 m/s), light breeze (1.6-3.3 m/s), moderate breeze (5.5-7.9 m/s), strong gale (20.8-24.4 m/s), and hurricane (32.7+ m/s). Weather stations worldwide measure wind speed in m/s using anemometers.
Ballistics and Firearms
Muzzle velocities of firearms and projectiles are specified in m/s internationally. A 9mm handgun bullet: approximately 370 m/s. An AK-47 rifle: approximately 715 m/s. A high-velocity rifle (.220 Swift): approximately 1,220 m/s. The speed of sound (Mach 1) at sea level is approximately 343 m/s, making these supersonic velocities readily comparable.
Sports Science
Sports performance is increasingly analyzed in m/s. Usain Bolt's peak speed during his 100 m world record was approximately 12.4 m/s. A professional tennis serve can reach 65 m/s (234 km/h). A golf ball off the tee reaches approximately 75-85 m/s. These measurements help coaches optimize athlete performance.
Everyday Use
Walking and Running
Average human walking speed is approximately 1.2-1.5 m/s (4.3-5.4 km/h). A brisk walk is about 1.8 m/s (6.5 km/h). Jogging speed is typically 2.5-4 m/s. A recreational runner covers a 5K in about 30 minutes at approximately 2.8 m/s. Elite marathon runners maintain approximately 5.5 m/s (20 km/h) for over two hours.
Quick Conversion Trick
To convert m/s to km/h, multiply by 3.6. This is exact and easy to remember: 10 m/s = 36 km/h, 20 m/s = 72 km/h, 30 m/s = 108 km/h. For approximate conversion to mph, multiply m/s by 2.24: 10 m/s ≈ 22.4 mph.
Wind and Weather
Wind speeds reported in m/s provide direct physical intuition. A gentle breeze of 3 m/s is comfortable. A wind of 10 m/s (36 km/h) makes walking difficult. A wind of 30 m/s (108 km/h) causes structural damage. A tornado wind of 70 m/s (252 km/h) is catastrophically destructive.
Sound and Echoes
The speed of sound in air at 20°C is approximately 343 m/s. This means sound takes about 3 seconds to travel 1 kilometer. The common method of counting seconds between lightning and thunder — with each 3 seconds representing roughly 1 km of distance — is a practical application of the speed of sound in m/s.
In Science & Industry
Fundamental Constants
The most important speed constant in physics — the speed of light in vacuum — is defined as exactly 299,792,458 m/s. This value, denoted c, appears in Einstein's mass-energy equivalence (E = mc²), special relativity, Maxwell's equations, and the definition of the meter itself. No information or matter can travel faster than c.
Fluid Dynamics
Fluid dynamics calculations use m/s for flow velocities. Reynolds number, the dimensionless quantity that predicts turbulence, is calculated using velocity in m/s: Re = ρvL/μ. Bernoulli's equation relates pressure and velocity in m/s. Computational fluid dynamics (CFD) simulations compute velocity fields in m/s across millions of mesh cells.
Seismology
Seismic waves travel through the Earth at speeds measured in m/s (or km/s). P-waves (primary, compressional) travel at 5,000-13,000 m/s through the crust and mantle. S-waves (secondary, shear) travel at 3,000-7,000 m/s. Surface waves travel at 2,000-4,500 m/s. These speeds depend on the density and elastic properties of the rock and are used to image Earth's interior.
Astrophysics
Astronomical velocities span an enormous range in m/s. The International Space Station orbits at 7,660 m/s. Earth's escape velocity is 11,186 m/s. The Sun moves through the Milky Way at approximately 220,000 m/s. Galaxies recede from each other at velocities measured as fractions of c, ultimately in m/s.
Interesting Facts
The speed of light is exactly 299,792,458 m/s — not approximately, but exactly. This is because the meter is defined as the distance light travels in 1/299,792,458 of a second, making the speed of light a defining constant rather than a measured value.
Usain Bolt reached a peak speed of approximately 12.4 m/s during his 9.58-second 100m world record in 2009. A cheetah can reach approximately 30 m/s (108 km/h), while a peregrine falcon in a dive (stoop) can exceed 100 m/s (360 km/h).
Sound travels at approximately 343 m/s in air at 20°C, but at about 1,480 m/s in water and 5,120 m/s in steel. This is why you can hear a train coming by putting your ear to the rail long before you hear it through the air.
The Earth orbits the Sun at approximately 29,800 m/s (107,000 km/h). Despite this enormous speed, we do not feel it because the motion is uniform and the entire atmosphere moves with us.
A sneeze expels air at approximately 45 m/s (160 km/h). A cough expels air at about 25 m/s. These speeds explain why respiratory droplets can travel several meters — a fact that became critically important during the COVID-19 pandemic.
The fastest man-made object ever is the Parker Solar Probe, which reached approximately 192,000 m/s (692,000 km/h) during its close approach to the Sun in 2024 — about 0.064% of the speed of light.