Talk:Joule-second

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The "joule second" is described differently when it describes power than when it describes angular momentum. It does need sorting out. I'm not sure I am the one to do it. Also, since its applications are electrical, optical, and mechanical, the measurements are understood differently depending upon the application, but the measurement is still equivalent. --Voyajer 01:09, 28 December 2005 (UTC)

This page is certainly mixed up. It starts off correctly discussing the joule second but it calls it first the "unit of power over time" when in reality it is the unit of energy multiplied by time.(It was correct when it mentioned to look elsewhere for the "joule/second" "see watt" which is a unit of power). It then rightfully calls it a unit of "action or a unit of angular momentum." Unfortunately it then gets mixed up again by discribing the term joule/second the unit of power. Will someone please fix it up. --A.Z.

Changes of 29 August 2012

User:MeasureIT reverted my change for "J·s". If (s)he looks at WP:MOSNUM, (s)he will see that symbols are joined a "middot", but words by a dash. Martinvl (talk) 03:32, 29 August 2012 (UTC)

I invited you to explain the difference between "J·s" and "J⋅s" and to explain why you were not referring to Wikipedia guidelines, but to the "SI manual". How about explaining here then. MeasureIT (talk) 06:46, 29 August 2012 (UTC)

What's the difference? There's another editor challenging the use of middot, saying it should be sdot, at Lumen second. MeasureIT (talk) 21:24, 30 August 2012 (UTC)

I agree: this page isn't clear: we don't understand the difference bewteen J/s and J*s (J/s is explained clearly in the last part, but not J*s). I added some illustrations taken from https://physics.stackexchange.com/questions/154451/what-do-units-like-joule-seconds-imply User67QH (talk) 11:49, 18 July 2020 (UTC)

Delete for dubious notability, Energy is not Torque

This article started out as "Joule per second". That couldn't be rendered well in the title which was "Joule-second" and somehow (probably because of that) the article morphed into talking about the "Joule-second". That makes sense except the notability of the "Joule-second" is extremely thin. Reliable secondary sources are required to establish notability. This article has been without any sources since it was started ten years ago (TEN!). The subject's notability has failed to be established since almost the beginning of Wikipedia. It's time to put this article out of its misery and delete it.

Also, since nobody has seen fit to delete dubious or unnotable material in this wholly uncited article, a number of bits of outrageous nonsense have crept in:
1) Energy is not Torque, Angular momentum is not measured in units of Energy-time.
2) The misinformation spreads: In at least one article (Spin (physics)), linking here promulgates the fallacy.

Just because two different things are measured in the same fundamental units doesn't mean they're the same thing.

Torque is a vector measured in Force-Length.
Energy is a scalar measured in Force-Length.

But, torque is not energy.

1) The thing that a force is multiplied by (integrated over) to make a unit of energy is a completely different thing that a force is multiplied by (actually a cross-product) to make a unit of torque. Both things are measured by length giving the same scalar units, but they're different things and the results are different things. For energy, the "length" to get force-length units is parallel to the force, while for torque it's perpendicular to the force.
2) Energy is a scalar while torque is a vector. Different "lengths" in plus different operations done makes for completely different things out (scalar v. vector).
3) Etc. Etc. Etc.

It's a rookie mistake to see the same units and presume they must be the same or somehow mysteriously related. Think about it, their physicalities are completely different, it's actually intuitive that they're different. But, some people get so bowled-over and blinded by the math that they don't stop to think about what's really going on.

96.230.106.141 (talk) 02:24, 24 March 2016 (UTC)

Yes, you are correct that two very different quantities can have the same units. Still it is helpful to at least mention what the units of a quantity are, and if they are the same another quantity then why not say so? A useful way to perform dimensional analysis is to know a few shortcuts, units of angular momentum and action is one of them. M∧Ŝc²ħεИ_τlk 17:22, 24 March 2016 (UTC)

Hi there. The reason to "not say so" is that saying so can accidentally imply that Energy and Torque are somehow mysteriously related. Or rather, we need to be careful to avoid wording that is too easily inferred to mean that the two are related. I think mentioning "Joules" when discussing Torque does that and it should be avoided.

If you take a look over in Torque#Units you'll see a warning to beware of writing so the two are confused, and to say "N-m" and not "Joule" when discussing Torque. There's also a ref for that precaution given there.

I think it would be great to mention the "problem" (of the incorrect appearance of the two being related), perhaps in the Torque article. And, I could probably draft some good words for it. But, it would be WP:OR because I don't have a source for it. If you have a source for it, I think it would be a fine thing to add somewhere.  :-)

96.230.106.141 (talk) 03:53, 25 March 2016 (UTC)

No-one is saying that two quantities with the same unit are the same or related quantities. Singling out action as the only quantity with units of Js, and not listing others, will make people wonder why are there not other quantities with the same units. But I don't have time to pursue this right now. M∧Ŝc²ħεИ_τlk 08:15, 25 March 2016 (UTC)