Talk:Kilometres per hour
From Wikipedia, the free encyclopedia
Contents |
[edit] pagename
Should this page's name be changed to "Kilometres per hour"? Vancouverguy 22:45, 17 Sep 2003 (UTC)
- Yes it should, I'll change it now. WikiSlasher 03:57, 18 June 2006 (UTC)
Why has someone changed the spelling from kilometre to kilometer. Kilometre with the "tre" is the standard worldwide spelling only Americans spell it that funny way G-Man 23:00, 17 Sep 2003 (UTC)
- No, in german it is also spelled de:Kilometer. --Thomas
- It's not just German and American English. You only have to hover of the language box on the left of the article to see that it's "meter" in many languages. --Multiplexor (talk) 17:15, 25 April 2008 (UTC)
[edit] kph
kph is a measurement of speed, not velocity
[edit] Scalar versus vector
I was under the impression that vectors require a direction. If so km/h could not be a vector, it would need to be 'x km/h, north' or something like that. I made an edit on that basis but it was reverted. Can this be clarified? Bobblewik (talk) 4 July 2005 17:44 (UTC)
- As the article force tells us, "A force can be represented by a vector with two properties: magnitude and direction." That doesn't mean that it would be wrong for it to say, as it does, that the "SI unit used to measure force is the newton," does it? Nor for newton to say that it "is the SI unit of force"?
- Why in the world would you think that velocity would be any different? As its own article says:
- "It is thus a vector quantity with dimension length/time. In SI units this is metre per second."
- Gene Nygaard 4 July 2005 18:20 (UTC)
-
- I don't know the answer. The following seemed plausible:
- The Difference Between Speed & Velocity
A scalar quantity is one which can be fully described by its size. Length, mass, temperature, energy, speed and volume are all scalar quantities. For example 20kg fully describes the mass of an object.
A vector quantity is one where you must also mention its direction. Force, velocity, displacement and acceleration are all vector quantities. For example a force of 20N can only be fully described by quoting its direction. 20N upwards will be different than 20N to the left.
- The Difference Between Speed & Velocity
- Direction may be implicit in many cases, but if that source is correct, a vector quantity without a direction is incomplete. Bobblewik (talk) 4 July 2005 22:07 (UTC)
- I don't know the answer. The following seemed plausible:
[edit] m/h
At Knot (speed) someone changed 'm/h' to 'metres per hour' because it looked too much like 'miles per hour'. That's fine with me, but I was wondering. Isn't that usually written as mph? Which would solve the ambiguity. And is 'm/h' an acceptable notation for 'metres per hour'? I suppose it is because in the metric system you can combine anything with anything. Although km/h and m/s are more common. DirkvdM 09:19, 15 September 2005 (UTC)
- You are right. The unit 'metres per hour' is correctly written as 'm/h'. The SI website clearly lists the:
- and the
- official symbol for 'hour'. Note that the SI unit of time is the second, not the hour. The hour just happens to be 'accepted for use' with SI units.
- As you might expect, the Wikipedia articles Metre and Hour repeat the official symbol. So there is no reasonable ambiguity with 'm/h' and it is incorrect to claim that there is.
- There are no internationally agreed symbols for 'miles per hour' so I cannot advise you on that. Note also that 'mph' is language dependent. One of the benefits of the metric system is that it does not depend on knowing the language, just as the international symbol for mercury is Hg. For example, 'miles per hour' and 'kilometres per hour' would be 'mao' and 'cao' in Italian.
- However, Wikipedia articles appear to accept 'mi/h' and 'mph' as forms for miles per hour. I think I have also seen 'mi/h' on speedometers. Either of those abbreviations work for me. Bobblewik 16:03, 24 September 2005 (UTC)
-
- Just because the official symbol for meters is m, and the symbol for hours (at least when used with SI) is h, that would only show that m/h can mean meters per hour, not that it cannot mean miles per hour. Good grief, even among the SI and units acceptable for use with it, we have the symbol 'rad' which can stand for two different units, rad and rad. We also have "nm" used for nautical miles, as well as the SI unit of lenghth, nanometers.
- For miles per hour, mi/h is better than mph, IMHO.
- But you will almost never see m/h used for miles per hour in current usage, so there is no real ambiguity. For that matter, you are probably even less likely to run into meters per hour in actual usage. So enough of this tilting at windmills. Gene Nygaard 17:17, 24 September 2005 (UTC)
-
-
- I suppose the '1852 metres per hour' in the article really should be changed to '1,852 km/h'. There is no need to use the uncommon 'metres per hour'. Also notice my use of a comma. I read in one thread that the SI rules say you can use either a comma or dot here (and the thousands-separator is a space). But don't worry, I'll use a dot :) .
- As for something like km/h being the same in all languages. That is alas not entirely true. Prefixes like 'kilo' are. And afaIk the same goes for the 'm' in all western languages, because the equivalents of 'metre' all happen to start with an 'm' (which isn't a total coincidence of course). But the 'h' isn't universal. It works in Spanish (hora) and French (heure) and I imagine in all Latin languages. But not in Dutch, where the word for 'hour' is 'uur', so it's 'km/u'. which made me wonder about German, inwhich the word for 'hour' is 'Stunde'. Which rather inconveniently starts with an 'S' (capital, but still). So I looked up the German article on km/h and it turns out they write it with an 'h'. Well, they had little choice. But then I looked up the same article in Dutch and there it is also written as km/h. Which surprises me, because most people (though not all) use km/u, even including me, and I am a very strong supporter of standardisation. I'll amend my ways forthwith :) . This however seems to be the only problem with SI base units (in western languages and as far as I know). 'Gram' starts with a 'g' in all languages, as does does 'second' with an 's'. And the others (A, K, mol, cd) seem to be too recent to have different names in different languages.
- I also Googled this. In Dutch pages km/u is just a little more common than km/h. I can't make a comparison for German because I wouldn't know what to test against, but km/h scores close to 2 million hits. So at least it's common. DirkvdM 07:26, 26 September 2005 (UTC)
- I am really supriced that the Dutch would have any ambiguity about this! The km/h is the international standard and the individual abrivitions don't come from the language of the particular country. F.ex. in Finland hour is "tunti", still kilometriä tunnissa is km/h as per SI (which itself stands for "Kansainvälinen yksikköjärjestelmä" in Finnish as in English although its a French acronym), day, "päivä" is d, year, "vuosi" is a and so forth, like in (scientific) English. And I assume the prefix "micro" is abrevieded with the Greek letter mu (μ) in Dutch too?82.181.150.151 21:42, 13 February 2007 (UTC)
-
[edit] Residential Limit
I was under the impression that residential areas are usually 20 or 25 mph, or about 30 or 40 km/h. Are they actually 50 km/h in metric countries? 50 km/h (about 30 mph) is a bit fast for a neighbourhood... koolman2 08:34, 30 September 2005 (UTC)
- In the UK residential limits are 30mph. In Australia residential limits are 50km/h (though 40km/h limits apply past schools during certain posted hours). YMMV! Graham 09:03, 30 September 2005 (UTC)
-
- Interesting! Thanks- koolman2 18:38, 30 September 2005 (UTC)
[edit] Image
- What the speed 50 km/h looks like on a normal bicycle
Does anyone else think that this is not really necessary. Firstly, what it looks like on the photo despends on the shutter speed of the camera. If the shutter speed is different, then the image would look very different too.
Also, does the image add any meaning to the article? Is it easier to picture what km/h means? Richard B 18:24, 18 December 2005 (UTC)
[edit] External links
The link that you currently have in your article points to a site that is an unauthorized copy of the other site. The original page of online speed conversion is http://www.convert-me.com/en/convert/speed The site http://www.convert-me.com/ exists for years (you can check http://www.archive.org) and the illegal copy linked from this article was only placed recently. As the owner of the original www.convert-me.com project, I'll be happy to provide any additional information and proofs of authenticity. My name is Sergey Gershtein and my contact info can be found on http://sergey.gershtein.net/ I think I will go ahead and edit the page changing the link to make it point to the original site.
- Also the other link is a broken one.
[edit] kph abbreviation
Is it really wrong? http://www.thefreedictionary.com/kph http://dictionary.reference.com/browse/kph http://webster.com/cgi-bin/dictionary?va=kph http://www.google.com/search?q=kph
All say kph is kilometers per hour.
- No, it's not wrong. Following standard practice for abbreviations, kilometres per hour = kph; if the standard abbreviation, km, is instead used for kilometres, then kilometres per hour becomes kmph; these are perfectly valid abbreviations. Unfortunately, an editor has, at some point, labelled them as incorrect because they are not the accepted standard abbreviations used in scientific discourse. (Just to be clear, this is not an anti-science comment; I am a scientist who uses kmh-1.) However, not being part of a standard does not make something incorrect—if it did we'd all be using metres per second anyway. ObfuscatePenguin 18:23, 20 September 2007 (UTC)
[edit] RfC: Should titles of article on units of the form "X per Y" be singular or plural?
I've moved the discussion to Wikipedia talk:Naming conventions#RfC: Should titles of article on units of the form "X per Y" be singular or plural?; the two of us (myself & User:Piercetheorganist) could have this discussion forever, and get nowhere fast. Hopefully, more people have that page on their watchlist, and will contribute. Oli Filth(talk) 13:59, 6 January 2008 (UTC)
[edit] Wiki converter
I would add an wiki online convertion page (to change from km/h to mph and viceversa).
Something similar to :
but applied to conversions :
<inputbox> type=? width=24 break=no buttonlabel=km/h to mph </inputbox>
