4 Units of Measurement from around the World
The four basic quantities of time, length, mass and force are related by Newton’s Law of Motion, F = net force = ma. So the units for these cannot be selected arbitrarily.
Système International (SI) Units or “the metric system”
The International System of Units, is abbreviated SI to honour the French “Système International d’Unités”. https://www.bipm.org/en/measurement-units/, from the Bureau International des Poids and Mesures. In 1901 they chose g at a standard location to equal g = 9.806 65 m/s2 or 9.81 m/s2 to three significant figures.
Length is in metres, time is in seconds, mass is in kilograms and force is in newtons where newtons are a derived unit.
The abbreviations are m, s, kg, N, where 1 N = 1 kg · m/s2.
U.S. Customary (FPS) or “the imperial system”
In the United States, one of only three countries to still use what is often called the Imperial System, is often called the FPS for foot-pound-second. https://www.zmescience.com/other/map-of-countries-officially-not-using-the-metric-system/
Length is measured in feet, time in seconds and force in pounds.
The abbreviations are ft, s, lb.
Mass is measured in a derived unit called a slug where 1 slug = 1 lb · s2/ft
Conversion of Units
1 pound = 1 lb = 4.448 N
1 slug = 14.59 kg
1 ft = 0.3048 m
The inch was redefined in terms of the metre such that 1 inch is exactly 0.0254 m in 1933.
Also, you will need to know that in the FPS system
1 foot = 1 ft = 12 inches = 12 in
5280 feet = 52890 ft = 1 mile = 1 mi
1000 pounds = 1 kip (kilo-pound)
2000 pounds = 1 ton
1000 kg = 1 metric ton 1 metric ton = 2204.6 pounds on the surface of the Earth where g = 9.80665
