- Planck momentum
**Planck Momentum**is the unit ofmomentum , denoted by $m\_P\; c$, in the system ofnatural units known asPlanck units .$m\_P\; c\; =\; frac\{hbar\}\{l\_P\}\; =\; sqrt\{frac\{hbar\; c^3\}\{G\; approx$ 6.52485 kg m/s

where

*$\{l\_P\}$ is the

Planck length

*$hbar$ is the reducedPlanck's constant

*$c$ is thespeed of light in avacuum

*$G$ is thegravitational constant In SI units Planck momentum is approximately 6.5 kg m/s. It is equal to the

Planck mass multiplied by thespeed of light , usually associated with the momentum of primordial photons in some prevailingBig Bang models. Unlike most of the otherPlanck units , Planck momentum occurs on a human scale. By comparison, running with a five-pound object (10^{8}×Planck mass) at an average running speed (10^{-8}×speed of light in a vacuum) would give the object Planck momentum. A 70 kg human walking at an average speed of 1 m/s would have a momentum of about 10.7 $m\_P\; c$.**See also***

Planck's constant

*Natural units **External links*** [

*http://www.planck.com/planckmomentum.htm http://www.planck.com/planckmomentum.htm*]

* [*http://www.pmmode.com/theory/planck_units.htm Planck units expressed as geometry of momentum*]

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