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December 28

Hammer and nail

Am I right in assuming that when a hammer head hits a nail, there is an almost instantaneous conplete transfer of momentum (assuming the hammer does not recoil) from the hammer head to the nail and that the transfer takes a very small amount of time. in other words, is it an inpulsive transfer of energy?? 80.2.23.3 (talk) 01:07, 28 December 2018 (UTC)[reply]

It will be quick but not quite an "instant" or zero time. The transfer of momentum will continue as long as the nail is being driven in, or it is being deformed by the impact. Our hammer article could do with more physics in it. Graeme Bartlett (talk) 03:04, 28 December 2018 (UTC)[reply]

That is entirely dependent on the timeframe or -resolution you choose to look at. There will be all the normal physical deformations in the nail but since it is very well constructed for its purpose of course the energy in the hammer will be mostly "transfered" to achieve the meant result. Btw., in physics the base concept of your "transfer of momentum" is Elastic collision. Since the main energy is then used for Deformation (mechanics) its a little more complicated to describe correctly. --Kharon (talk) 07:41, 29 December 2018 (UTC)[reply]

reducing methane emissions from hydroelectric power plants

how can methane emissions from hydroelectric power plants be reduced? — Preceding unsigned comment added by Tokk.Tokk (talk • contribs) 02:38, 28 December 2018 (UTC)[reply]

One way would be to switch to nuclear. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:48, 28 December 2018 (UTC)[reply]

~~Here's a report on the general subject.[1]~~ ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:50, 28 December 2018 (UTC)[reply]

Well that was a report on natural gas plants. Hydroelectric power plants will have a dam that could have anaerobic conditions where methane is produced. One way to reduce emissions would be to remove organic matter before the dam is filled with water, eg cut down the trees, scrape off the undergrowth and soil. Graeme Bartlett (talk) 02:53, 28 December 2018 (UTC)[reply]

This article from 2014 says scientists are in the "early stages" of study of this phenomenon, but the causes are plainly obvious, and square with what Graeme says.[2] ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:44, 28 December 2018 (UTC)[reply]

Sounds like fixing at the wrong end. Most "artificial" methane comes from the flood of manure all the lifestock produces that we keep to produce all the cheap meat we want. --Kharon (talk) 07:00, 29 December 2018 (UTC)[reply]

Again huh? Do you actually have a source for this? I'm not disagreeing that livestock are a big contributor to methane. Although not so much from manure, which is a problem but AFAIK isn't a major contributor to methane, instead most methane comes from cow belches. More importantly, the above source explicitly says

Scientists are searching for answers to that question, as they study how much methane is emitted into the atmosphere from man-made reservoirs built for hydropower and other purposes. Until recently, it was believed that about 20 percent of all man-made methane emissions come from the surface of reservoirs. New research suggests that figure may be much higher than 20 percent, but it’s unclear how much higher because too little data is available to estimate.

and

Methane emissions from livestock are the second-largest source of methane emissions in the U.S., behind crude oil and natural gas, according to the U.S. Environmental Protection Agency. But the EPA’s greenhouse gas emissions estimates do not yet account for methane emissions coming from man-made reservoirs. Part of the reason is that, generally, very little is known about reservoirs and their emissions, especially in temperate regions, such as in the U.S., where few studies have been conducted. In 2012 study, researchers in Singapore found that greenhouse gas emissions from hydropower reservoirs globally are likely greater than previously estimated, warning that “rapid hydropower development and increasing carbon emissions from hydroelectric reservoirs to the atmosphere should not be downplayed.” Those researchers suggest all large reservoirs globally could emit up to 104 teragrams of methane annually. By comparison, NASA estimates that global methane emissions associated with burning fossil fuels totals between 80 and 120 teragrams annually.

The NASA estimate link still works although it isn't maintained. And it says "Animals contribute about 80 Tg methane per year".

Nil Einne (talk) 12:35, 31 December 2018 (UTC)[reply]

Again what? Are you demanding that i add sources to anything i write here now? Btw. I was refering to "man made" aka "artificial" methane, since the question was about "artificial pools" generating methan. Not about natural deposits getting accessed.--Kharon (talk) 17:50, 31 December 2018 (UTC)[reply]

(cite)"Identifying it as “a major threat to the environment” (FAO 2006), the FAO found that the animal agriculture sector emits 18%, or nearly one-fifth, of human-induced GHG emissions, more than the transportation sector. (Steinfeld et al. 2006).
::Our objective was to outline the animal agriculture sector’s share of global GHG emissions by synthesizing and expanding upon the data reported in Livestock’s Long Shadow (FAO 2006) with more recent reports from the IPCC, data from the U.S. Environmental Protection Agency (EPA), and studies on GHGs from agriculture and mitigation strategies [Cederberg and Stadig 2003; International Federation of Organic Agriculture Movements (IFOAM) 2004; IPCC 2007a, 2007b, 2007c; McMichael et al. 2007; Ogino et al. 2007; U.S. EPA 2007a; Verge et al. 2007]. We also investigated links between this sector and the far-reaching impacts of climate change on conflict, hunger, and disease, while underscoring the roles of animal agriculture industries, policy makers, and individual consumers in mitigating this sector’s contributions to climate change and global warming.
"(citeend)(Environmental Health Perspectives, May 2008

This is the reference desk, so yes you should be providing sources for anything you write here, especially when it's something which isn't obvious and is probably incorrect. Someone has been topic banned from here in the past in part due to their persistence in never providing sources. Your response is largely unrelated to anything I've said. You explicitly claimed that 'Most "artificial" methane comes from the flood of manure all the lifestock produces that we keep to produce all the cheap meat we want'. This is disputed by the source already linked which suggests emissions from reservoirs could actually exceed that from livestock. I already acknowledged that methane production from livestock, mostly cattle is a serious concern. However as I also said, this doesn't mean, as your first response claimed, that methane from hydropower reservoirs is not a concern. You've provided zero evidence it is not a significant concern, whereas the evidence suggests it is a significant concern. BTW, GHG emissions from animal agriculture are not simply methane. Note also that methane emissions from fossil fuels related to human activity are generally counted as an anthropogenic source of methane per the NASA source, whether or not you want to count it as artificial, although as said this is largely besides my point. Nil Einne (talk) 22:53, 31 December 2018 (UTC)[reply]

BTW, I had a little time to look into methane from animal manure and found [3] [4] [5]. Based on these, I will refine my earlier comment from "Although not so much from manure, which is a problem but AFAIK isn't a major contributor to methane, instead most methane comes from cow belches." to "Although not so much from manure, which is a problem but AFAIK is a far smaller contributor to methane then enteric process i.e. most methane from livestock comes from cow belches not manure." as methane from manure is higher than I had thought. Nil Einne (talk) 23:33, 31 December 2018 (UTC)[reply]

Happy to learn something every day. --Kharon (talk) 12:07, 1 January 2019 (UTC)[reply]