Commonly used units of measurement

Metric System

The metric system is an international decimalized system of measurement. It is also commonly referred to as SI (from the French Le Système International dUnités). It is used by all countries in the world except for the United States and Myanmar.

The metric system is based on the meter, the litre and the gram as the base units of length, capacity, and weight or mass, respectively. The metric system also includes the kelvin and the candela as base units of temperature and luminosity.

All other units of measurement are derived from these base units. For example, the kilogram is derived from the gram and the millimeter is derived from the meter. Other derived units such as the hertz, watts, newtons, and pascals are derived from these base units as well.

Metric System Prefixes

A unique feature of the metric system is the use of metric prefixes. These are used to denote multiples and fractions of the base unit. For example, the kilometer (km) is a unit derived from the meter, and it is equal to 1000 meters. This can be represented by the prefix “kilo-” which means “thousand.”

The prefixes for the metric system are as follows:

• kilo- (k) = thousand

• hecto- (h) = hundred

• deka- (da) = ten

• deci- (d) = tenth

• centi- (c) = hundredth

• milli- (m) = thousandth

• micro- (µ) = millionth

• nano- (n) = billionth

• pico- (p) = trillionth

Examples of Units

The metric system is used for many different measurements, including the following:

• Length: meter (m), millimeter (mm), kilometer (km)

• Mass/Weight: gram (g), kilogram (kg), tonne (t)

• Area: square meter (m2), hectare (ha)

• Volume/Capacity: liter (L), cubic meter (m3)

• Temperature: Kelvin (K), Celsius (°C)

• Time: second (s), minute (min), hour (h)

• Frequency: hertz (Hz), terahertz (THz)

• Force: newton (N)

• Pressure: pascal (Pa)

• Power: watt (W), kilowatt (kW)

Conclusion

The metric system is an international system of measurement based on the meter, the litre and the gram as the base units of length, capacity, and weight or mass, respectively. The metric system also includes the kelvin and the candela as base units of temperature and luminosity. Metric prefixes are used to denote multiples and fractions of the base units and are used for a variety of different measurements.

The metric system is used by virtually all countries in the world and is essential for scientific measurements and calculations.

The International System of Units (SI units) is used to define the units of measurement. SI units provide a uniform application of physical quantities and are based on seven base units. The SI base units are the meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol) and candela (cd).

The meter (m) is defined as the length of the path traveled by light in a vacuum in 1/299，792，458 of a second. The kilogram (kg) is the unit of mass and is equal to the mass of the international prototype of the kilogram. The second (s) is the unit of time and is based on the duration of 9，192，631，770 periods of radiation corresponding to the transition between two energy levels of the cesium-133 atom. The ampere (A) is the unit for electric current and is equal to the constant current that, if maintained in two infinitely long wires of uniform cross-section and placed 1 meter apart in a vacuum, would produce a force of 2 x 10-7 newtons per meter. The unit of temperature is the kelvin (K). The kelvin is defined as 1/273.16 of the thermodynamic temperature of the triple point of water. The unit of the amount of a substance is the mole (mol). The mole is defined as the amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12. The candela (cd) is the unit of luminous intensity and is defined as the luminous intensity of a monochromatic radiation of frequency 540×1012 hertz and a radiating intensity of 1/683 watt per steradian.

The SI base units are also commonly used for non-SI units. For example, the light year is defined as 9.4605284×1012 kilometers, the watt is defined as 1 joule per second and the astronomical unit is defined as 1.495978707× 1011 meters.

In addition to the SI base units, the following derived units are used in scientific and engineering applications: the hertz (Hz), a unit of frequency; the newton (N), a unit of force; the pascal (Pa), a unit of pressure; the joule (J), a unit of energy; and the watt (W), a unit of power.

The International System of Units (SI units) is used around the world to provide consistent measurements of physical phenomena. The SI base units and derived units are used to describe the behavior of all types of physical systems through the application of mathematics, which allows for accurate and reliable results.