Joule-second: Difference between revisions
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the article did not say that action and angular momentum are "the same" just because the units are the same. restricting one units per quantity is unhelpful and annoying, see talk page |
Removed uncited WP:OR. It's misleading to mention the coincidental "Joule grouping" (N-m) in the context of Angular momentum because it's too easily inferred to imply a sameness of energy and torque. (see talk page) |
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{{For|information about the unit "joule/second"|watt}} |
{{For|information about the unit "joule/second"|watt}} |
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{{Unreferenced|date=December 2009}} |
{{Unreferenced|date=December 2009}} |
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The '''joule-second''' ('''J s''' or '''J·s''') is a unit equal to a [[joule]] multiplied by a [[second]] |
The '''joule-second''' ('''J s''' or '''J·s''') is a unit equal to a [[joule]] multiplied by a [[second]], used to measure [[action (physics)|action]]. The [[action (physics)|action]] of a system has the dimensions of [[energy]] integrated over [[time]]; it is therefore measured in joule-seconds. The joule-second is the unit used for [[Planck's constant]]. |
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In [[SI]] base units, the joule-second is <math>\frac{kg \cdot m^{2}}{s}=J \cdot s.</math> |
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Angular momentum has [[dimensional analysis|dimensions]] of [[length]] times [[momentum]], [length]·[momentum] = [length]·[mass]·[length]·[time]<sup>−1</sup> = [mass]·[length]<sup>2</sup>·[time]<sup>−1</sup> = [energy][time]. In [[SI]] base units, the joule-second is kg·s·m<sup>2</sup>·s<sup>−1</sup> = J·s. |
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Action is the [[Lagrangian mechanics|Lagrangian]] (which has same units as energy) integrated over time, therefore its dimensions are [energy]·[time]. |
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Although these two are different quantities, they have the same unit and [[angular momentum quantization]] can be expressed in units of the quantum of action, the reduced [[Planck's constant]] ''ħ'' = ''h''/2''π''. |
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{{DEFAULTSORT:Joule-Second}} |
{{DEFAULTSORT:Joule-Second}} |
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Revision as of 03:59, 25 March 2016
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The joule-second (J s or J·s) is a unit equal to a joule multiplied by a second, used to measure action. The action of a system has the dimensions of energy integrated over time; it is therefore measured in joule-seconds. The joule-second is the unit used for Planck's constant.
In SI base units, the joule-second is
