Kilogram (KG)
- is the SI unit of mass
- it is defined by taking the fixed numerical value of the Planck constant โ to be 6.626 x 10โ34 when expressed in the unit ๐ฝยท๐ , which is equal to ๐๐ยท๐2ยท๐ โ1, where the meter (๐) and the second (๐ ) are defined in terms of ๐ and ฮ๐ฃ๐ถ๐
KG - Timeline of Previous Definition
Theย International Prototype of the Kilogram, whose mass was defined to be one kilogram from 1889 to 2019.
- 1793: Theย graveย (the precursor of the kilogram) was defined as the mass of 1ย literย (dm3) of water, which was determined to be 18841ย grains.
- 1795: the gram (1/1000ย of a kilogram) was provisionally defined as the mass of one cubicย centimeterย of water at the melting point of ice.
- 1799: Theย Kilogramme des Archivesย was manufactured as a prototype. It had a mass equal to the mass of 1ย dm3ย of water at the temperature of its maximum density, which is approximately 4ย ยฐC.
- 1875โ1889: Theย Metre Conventionย was signed in 1875, leading to the production of theย International Prototype of the Kilogramย (IPK) in 1879 and its adoption in 1889.
- 2019: The kilogram wasย definedย in terms of theย Planck constant, theย speed of light,ย and theย hyperfine transition frequency ofย 133Csย as approved by theย General Conference on Weights and Measuresย (CGPM) on November 16, 2018.