Talk:Mach number

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Contents 1 Pronunciation 2 When an aircraft exceeds Mach 1... 3 Speeds 4 Images 5 I don't get it. 6 mach number and propagation of sound waves 7 Remove the PAF reference 8 Ernst Mach 9 Speed of Sound depends on Pressure 10 Mach speed decreases with altitude?

[edit] Pronunciation

(Ernst) Mach is definitely pronounced like (Johann Sebastian) Bach, therefore {max}. "Mach" is also in German the imperative of "to do". "Mach etwas" means "do something".

But "Mach" (of Ernst) has got a long "a", and "Mach" in "Mach etwas" a short one. Other than that, I agree, it's like "Bach". "Mack" or "Mock" are nonsense. 80.75.192.71 08:38, 18 July 2007 (UTC)

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Is Mach number really pronounced, as the article says, "mack" in British English and "mock" in American English? The reason I ask is that there has been some discussion on how Mach kernel is pronounced. In the discussion there (see Talk:Mach_kernel), some presume it is named after Austrian physicist Ernst Mach, and was pronounced the same as his name (like Bach). This would contradict to the information in this article about Mach number. So, the question really is, how is Ernst Mach pronounced (plus possible variants/alternatives)? Then, is Mach number named after his, yes or no? And if it is, is it pronounced like him or differently and why? And finally, is Mach kernel named after Ernst Mach and/or after Mach number and/or something else, and how and why is it pronounced (plus possible variants/alternatives)?

[edit] When an aircraft exceeds Mach 1...

When an aircraft exceeds Mach 1 a large pressure difference is created just in front of the aircraft. This pressure difference, called a shock wave, spreads backward and outward from the aircraft in a cone shape. It is this shock wave that causes the sonic boom heard as fast moving aircraft travels over head.

What was wrong with this paragraph, and how can it be fixed? AxelBoldt 00:27 Oct 3, 2002 (UTC)

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Removed warp speed reference. It's not correct even in the ST universe. Roadrunner 17:58, 30 Mar 2004 (UTC)

[edit] Speeds

Wanting opinions before making an edit I'm unsure of: Would it be beneficial to list, on the table, speeds (in kph, or mph, or m/s, or whatever) corresponding to each Mach number at typical temperatures and pressures? -FZ 22:21, 3 Aug 2004 (UTC)

I'm for creating a simple, small table of mach numbers at sea level and standard operational temperatures. If I were a middle or high school kid looking up mach numbers, I'd probably expect to find something like that on this page. --ABQCat 00:26, 1 Sep 2004 (UTC)

Ditto --Teradon 01:19, 27 April 2006 (UTC)

[edit] Images

I think that the images on this page are terrifically illuminating and valuable, but they are all taken from http://www.kurssit.lut.fi/040301000/main/11_3_2.html. User:Prkl75 added the images to Wikipedia and this article. There may be some copyright issues (despite the claim on the image pages), so if anyone happens to have some images that would work for this page in place of those aleady in use, I think that would be good. --ABQCat 00:50, 1 Sep 2004 (UTC)

The main image on the page is captioned "An F/A-18 Hornet breaking sound barrier". The caption implies that we can tell it is travelling supersonically from the visible condensation disc behind it. Other sources on the internet suggest this is an example of condensation from the Prandtl-Glauert singularity, and is not indicative of supersonic flow.JBel 16:11, 31 January 2007 (UTC)

The air flow diagrams are actually wrong because they depict the Equal transit-time fallacy. 142.103.207.10 (talk) 21:37, 8 February 2008 (UTC)

[edit] I don't get it.

I don't understand. How are sound and the sonic boom effect related? Do sound waves have anything to do with this or are they unrelated?

This is partially addressed in the article, "When an aircraft exceeds Mach 1 (i.e. the sound barrier) a large pressure difference is created just in front of the aircraft. This abrupt pressure difference, called a shock wave, spreads backward and outward from the aircraft in a cone shape (a so-called Mach cone). It is this shock wave that causes the sonic boom heard as fast moving aircraft travels overhead...".

I think what could help any discussion here is if you were to ask a specific question which would potentially benefit the article through an explanation here and future inclusion into the article if needed. I think you may be looking more for an article such as "sonic boom" which has a less technical discussion of the phenomenon (some of which may actually benefit this article, if only to point non-technical readers to a more apropriate article for their inquiries). --ABQCat 19:54, 2 September 2005 (UTC)

[edit] mach number and propagation of sound waves

How can one show the diagrams for the propagation of the sub-sonic, sonic and supersonic waves in form of their concentric circles formed and also their mach angle?

[edit] Remove the PAF reference

Even though I'm Pakistani myself, I do not agree with putting the PAF page here. It does not contain generic information related to the unit of measure, and is a patriotic page. It does not belong here.

Link removed.

It was added again. I'll remove it, the link doesn't even work. Keta 21:17, 10 June 2006 (UTC)

High-speed flow around objects

High speed flight can be classified in five categories: can thee following info also put in brackets in addition like as follows:

   * Subsonic: Ma < 1
   * Sonic: Ma = 1
   * Transonic: 0.8 < Ma < 1.2 [0.8 Ma - 1.2 Mach]
   * Supersonic: 1.2 < Ma < 5 [1.2 Ma - 5 Mach]
   * Hypersonic: Ma > 5

Newbies and dummies like me find it easier this easier.

[edit] Ernst Mach

was Czech...not Austrian...

[edit] Speed of Sound depends on Pressure

In general, the speed of sound depends on the pressure of the medium. This is the main reason why the speed of sound decreases with increasing altitude. Of course, temperature also has an effect on pressure and thereby also affecting slightly the speed of sound. Didi7 12:04, 18 January 2007 (UTC)

According to the Speed of sound article you have this backwards. The temperature is the important quantity. "Air pressure has no effect at all in an ideal gas approximation." Spiel496 21:41, 27 January 2007 (UTC)

[edit] Mach speed decreases with altitude?

If actual speed at Mach 1 increases with altitude, why do the numbers in the overview decrease? BQZip01 18:31, 27 February 2007 (UTC)

Huh? 'Mach 1 increases with altitude', where does the article say that? Temperature goes down with altitude.WolfKeeper 18:43, 27 February 2007 (UTC)

The temperature drops, but the air density does too. As for the reference "So, an aircraft travelling at Mach 1 at sea level (340.3 m/s, 1,225.08 km/h) will experience shock waves in much the same manner as when it is travelling at Mach 1 at 11,000 m (36,000 ft), even though it is travelling at 295 m/s (654.632 MPH, 1,062 km/h, 86% of its speed at sea level)." If this were the case, aircraft would fly lower to fly faster (which makes precious little sense). P.S. please don't take this as criticism, I just am confused. It may be one of those things that is counterintuitive BQZip01 18:54, 27 February 2007 (UTC)

Still awaiting an answer on this one BQZip01 14:59, 14 March 2007 (UTC)

Mach number is just a number that describes some aspect of the flow around the vehicle. The vehicles in general are trying to minimise drag for the speed that they are travelling at. This in general can be done at an optimum altitude for the current vehicle mass/weight, which varies over the length of the flight. As the vehicle weight goes down, the vehicle's ballistic coefficient is reduced and the vehicle needs to fly higher to maintain the same fuel efficiency over the ground. At low altitude the mach number would be the same or lower as at higher altitude, but the air drag would be much higher as well, so the fuel economy would suffer.WolfKeeper 02:12, 18 March 2007 (UTC)