# Thread: why mach no ?

1. In aeronautics ,why do we use Mach number as a reference 4 speed, and not jst simply knots, kph or mph etc.............We know the drag increases around Mach 1, giving the impression once upon a time tht der was a barrier der there. Is that the only reason.

2.

3. they do, Mach 1 just designates thge speed of sound at the given conditions-simple , no?

4. I believe Mach was the first to determine the speed of sound in the atmosphere. Hence, the designation.

5. what i think is that designating in terms of mach is easy when compared to other units(of speed) . moreover Mach 1 is the sonic speed & if more then 1 it is supersonic....... etc , which is easy to understand and calculate....

6. It's not a trivial calculation, as it depends on pressure, temperature, humidity, etc

7. So, Mach #/speed ratio changes if those conditions change (pressure, temperature, humidity, etc)?

I think I'll just stick with meters per second then. A lot easier to keep track of.

8. Yes, that's correct. In common usage, it is used as a multiple of the speed of sound under standard temperature and pressure. But that's really not the definition.

It really is tied to whether the flow under the conditions is faster or slower (and if faster, by how many times) than the speed of sound under those same conditions.

9. Sorry if this was already answered. Is mach always used by that specific standard or is it always preferred in reference to the local conditions?

since it's realted to the speed of sound, technically, local conditions are the standard.

10. as a child, the advent of the x-planes /rocket ships attaining anf surpassing the speed of sound mach1 were a constant delight
then the supersonic craft and saying mach 7 instead of 5376 mph is a tad easier

///edit thanx to waynes comment

11. sculptor,

Please stop posting nonsense in the Physics forum.

Just a friendly suggestion for now...

12. Originally Posted by halorealm
Sorry if this was already answered. Is mach always used by that specific standard or is it always preferred in reference to the local conditions
Accidental edit, no changes were actually made. I hit the wrong button.

13. Originally Posted by halorealm
Sorry if this was already answered. Is mach always used by that specific standard or is it always preferred in reference to the local conditions?

since it's realted to the speed of sound, technically, local conditions are the standard.
Since it's related to the speed of sound, local conditions are the reference. Technically. In popular usage (even by NASA, which drives me nuts) that's not always the case.

14. Originally Posted by MeteorWayne
sculptor,

Please stop posting nonsense in the Physics forum.

Just a friendly suggestion for now...
maybe you're too young to remember the x planes and the first breaking of the sound barrier?

15. But you said the speed of light... so it's nonsense. And I remember the X-planes very well, thank you.

"attaining anf surpassing the speed of light mach1 "

16. Originally Posted by MeteorWayne
But you said the speed of light... so it's nonsense. And I remember the X-planes very well, thank you.

"attaining anf surpassing the speed of light mach1 "
oops speed of light was a mistake
speed of sound is what i meant
thanx
to quote richard nixon
"I misspoke myself"

and now x-15 and x-43

17. It's what I pointed out elsewhere: you aren't using your left brain.

18. do you think it'd help if i closed my left eye?

19. I'm inclined to think if you closed both eyes and typed randomly on the keyboard it would make precious little difference.

Edit: The views expressed in this post are solely those of the entity known as John Galt. They reflect a distaste for misplaced poetry and metaphor, contrived expression of ideas, incidental obfuscation and inflated lexical constructions. They should be taken as seriously as one wishes, or not.

20. Originally Posted by John Galt
I'm inclined to think if you closed both eyes and typed randomly on the keyboard it would make precious little difference.

Edit: The views expressed in this post are solely those of the entity known as John Galt. They reflect a distaste for misplaced poetry and metaphor, contrived expression of ideas, incidental obfuscation and inflated lexical constructions. They should be taken as seriously as one wishes, or not.

closing my eyes...and
dnonsna;lud ckj zl ckjniiuf slkmdjd niuhjbnasyhiosjahuvjdsnhiu
did that do IT for you?
hell, i'l try almost anything once

(you got the physiological left eye to right brain reference?)

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