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joule (SI unit) J The work done when a force of one newton moves the point of its application a distance of one metre in the direction of the force. [32] = 1 J = 1 m⋅N = 1 kg⋅m 2 /s 2 = 1 C⋅V = 1 W⋅s kilocalorie; large calorie: kcal; Cal ≡ 1000 cal IT = 4.1868 × 10 3 J: kilowatt-hour; Board of Trade Unit: kW⋅h; B.O.T.U. ≡ 1 kW × 1 h
The diameter of the Sun is about 4.643 light-seconds. The average distance between Earth and the Sun (the astronomical unit) is 499.0 light-seconds. Multiples of the light-second can be defined, although apart from the light-year, they are more used in popular science publications than in research works. For example:
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The Jiffy is the amount of time light takes to travel one femtometre (about the diameter of a nucleon). The Planck time is the time that light takes to travel one Planck length. The TU (for time unit) is a unit of time defined as 1024 μs for use in engineering. The svedberg is a time unit used for sedimentation rates (usually
In physics, natural unit systems are measurement systems for which selected physical constants have been set to 1 through nondimensionalization of physical units.For example, the speed of light c may be set to 1, and it may then be omitted, equating mass and energy directly E = m rather than using c as a conversion factor in the typical mass–energy equivalence equation E = mc 2.
The units of the first two quantities are the ampere and the ampere per centimetre respectively. The unit of magnetic permeability is that of the emu system, and the magnetic constitutive equations are B = (4 π /10)μH and B = (4 π /10)μ 0 H + μ 0 M. Magnetic reluctance is given a hybrid unit to ensure the validity of Ohm's law for magnetic ...
Conversion of units is the conversion of the unit of measurement in which a quantity is expressed, typically through a multiplicative conversion factor that changes the unit without changing the quantity. This is also often loosely taken to include replacement of a quantity with a corresponding quantity that describes the same physical property.
One example is represented by the conditions in the first 10 −43 seconds of our universe after the Big Bang, approximately 13.8 billion years ago. The four universal constants that, by definition, have a numeric value 1 when expressed in these units are: c, the speed of light in vacuum, G, the gravitational constant, ħ, the reduced Planck ...