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Planck units modified so that 8 π G = 1 are known as reduced Planck units, because the Planck mass is divided by √ 8 π. Also, the Bekenstein–Hawking formula for the entropy of a black hole simplifies to S BH = ( m BH ) 2 /2 = 2 π A BH .
The formula defines the energy E of a particle in its rest frame as the product of mass (m) with the speed of light squared (c 2). Because the speed of light is a large number in everyday units (approximately 300 000 km/s or 186 000 mi/s), the formula implies that a small amount of mass corresponds to an enormous amount of energy.
The limit obtained depends on the model used: if the massive photon is described by Proca theory, [60] the experimental upper bound for its mass is about 10 −57 grams; [61] if photon mass is generated by a Higgs mechanism, the experimental upper limit is less sharp, m ≤ 10 −14 eV/c 2 (roughly 2 × 10 −47 g). [60]
the speed of light c, which when combined with the second, defines the length of the metre, and the Planck constant h, which when combined with the metre and second, defines the mass of the kilogram. The formal definition according to the General Conference on Weights and Measures (CGPM) is: The kilogram, symbol kg, is the SI unit of mass.
If a first body of mass m A is placed at a distance r (center of mass to center of mass) from a second body of mass m B, each body is subject to an attractive force F g = Gm A m B /r 2, where G = 6.67 × 10 −11 N⋅kg −2 ⋅m 2 is the "universal gravitational constant". This is sometimes referred to as gravitational mass.
In this context, "speed of light" really refers to the speed supremum of information transmission or of the movement of ordinary (nonnegative mass) matter, locally, as in a classical vacuum. Thus, a more accurate description would refer to c 0 {\displaystyle c_{0}} rather than the speed of light per se.
Kinetic energy per unit mass: 1 / 2 v 2, where v is the speed (giving J/kg when v is in m/s). See also kinetic energy per unit mass of projectiles . Potential energy with respect to gravity, close to Earth, per unit mass: gh , where g is the acceleration due to gravity ( standardized as ≈9.8 m/s 2 ) and h is the height above the ...
mass "The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10 −34 when expressed in the unit J s, which is equal to kg m 2 s −1, where the metre and the second are defined in terms of c and ∆ν Cs." [1] The mass of one litre of water at the ...