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  2. Electron - Wikipedia

    en.wikipedia.org/wiki/Electron

    The invariant mass of an electron is approximately 9.109 × 10 −31 kg, [80] or 5.489 × 10 −4 Da. Due to mass–energy equivalence, this corresponds to a rest energy of 0.511 MeV (8.19 × 10 −14 J). The ratio between the mass of a proton and that of an electron is about 1836.

  3. TNT equivalent - Wikipedia

    en.wikipedia.org/wiki/TNT_equivalent

    TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion.The ton of TNT is a unit of energy defined by convention to be 4.184 gigajoules (1 gigacalorie), [1] which is the approximate energy released in the detonation of a metric ton (1,000 kilograms) of TNT.

  4. History of United States postage rates - Wikipedia

    en.wikipedia.org/wiki/History_of_United_States...

    For another example, Charlotte May Pierstorff, then a 48.5-pound (22.0 kg) five-year-old, was mailed via parcel post in 1914; she survived, but the regulations were clarified to prohibit the use of parcel post for human transport. [26] Bulk postal rates were restructured in 1996: [citation needed] Second Class became Periodicals

  5. List of unusual units of measurement - Wikipedia

    en.wikipedia.org/wiki/List_of_unusual_units_of...

    This was an official unit of measurement in South Africa until the 1970s, and was defined in November 2007 by the South African Law Society as having a conversion factor of 1 morgen = 0.856 532 hectares. [27] This unit of measure was also used in the Dutch colonial province of New Netherland (later New York and parts of New England). [28] [29]

  6. Energy density - Wikipedia

    en.wikipedia.org/wiki/Energy_density

    In light-water reactors, 1 kg of natural uranium – following a corresponding enrichment and used for power generation– is equivalent to the energy content of nearly 10,000 kg of mineral oil or 14,000 kg of coal. [16] Comparatively, coal, gas, and petroleum are the current primary energy sources in the U.S. [17] but have a much lower energy ...

  7. Imperial units - Wikipedia

    en.wikipedia.org/wiki/Imperial_units

    The former Weights and Measures office in Seven Sisters, London (590 Seven Sisters Road). The imperial system of units, imperial system or imperial units (also known as British Imperial [1] or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed through a series of Weights and Measures Acts and amendments.

  8. Uranium - Wikipedia

    en.wikipedia.org/wiki/Uranium

    The Earth's crust from the surface to 25 km (15 mi) down is calculated to contain 10 17 kg (2 × 10 17 lb) of uranium while the oceans may contain 10 13 kg (2 × 10 13 lb). [11] The concentration of uranium in soil ranges from 0.7 to 11 parts per million (up to 15 parts per million in farmland soil due to use of phosphate fertilizers ), [ 63 ...

  9. Oscillation - Wikipedia

    en.wikipedia.org/wiki/Oscillation

    An undamped spring–mass system is an oscillatory system. Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states.