# Introductory Classical Mechanics/Units of Measurement

In general a *Unit of Measurement* is a term which describes a physical phenomena. The system of measurements used almost universally in physics is the SI, or metric system. The fundamental units of any system quantify distance, mass, time, temperature, electric current, brightness of light, and quantity of matter. The units and abbreviations are the meter(m) , kilogram (kg), second (s), kelvin (K), ampere (A), candela (cd), and the mole (mol).

## The Fundamental Units[edit | edit source]

### The meter[edit | edit source]

The meter is the fundamental unit of distance. It is defined as the distance a beam of light travels in a perfect vacuum in 3.33564095 billionths of a second.

### The kilogram[edit | edit source]

The kilogram is the fundamental unit of mass. A kilogram is the exact mass of a sample of platinum iridium kept in the International Bureau of Weights and Measures.

### The second[edit | edit source]

The second is the fundamental unit of time. It is the time taken for an atom of cesium to oscillate through 9.192631770 billion cycles.

### The kelvin[edit | edit source]

The kelvin is the fundamental unit of temperature, equivalent to the temperature increment of .003661 part of the thermodynamic temperature of the triple point of water.

### The ampere[edit | edit source]

The ampere, or amp, is the fundamental unit of current. The definition is that an ampere is the amount of constant charge carrier flow through two straight, parallel, infinitely thin wires placed 1 meter apart in a vacuum that results in a force between the conductors of 10 millionths of a Newton per linear meter.

### The candela[edit | edit source]

The candela is the unit of luminous intensity. It equals 1/683 of a watt of radiant energy at a frequency of 54 terahertz in a solid angle of one steradian.

### The mole[edit | edit source]

The mole is the quantity of particles that has a mass in grams equal to the molecular weight of said particle. It is equal to Avogadro's number, or 6.02×10^23 particles

## Derived units[edit | edit source]

Derived units are units that are products of fundamental units

### The newton[edit | edit source]

The newton is the unit of force, equivalent to one kg*m/s^2.

### The joule[edit | edit source]

The joule is the unit of energy or the result of a force acting through a distance. One joule is equal to one newton meter.

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