alleryThe kilogram is now defined using which fixed constant of nature?
AMass of an electron
BAvogadro number
CGravity on Earth
DPlanck constant
Answer & Solution
Correct answer: D. Planck constant
1. The metal prototype was found to drift by about 50 micrograms.
2. So the kilogram was redefined in 2019 using the Planck constant, the speed of light and a caesium frequency.
3. Earth's gravity is not a constant of nature and is never used to define mass.
_Source: Wikipedia, Kilogram, Timeline of previous definitions_
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