Unit conversion confusion

[divine`]

Part of my coursework (different subject) involves following an example of calculations for test piece A and so doing the same for B,C and D.

At the end stage there is a unit conversion that has me confused.

18.28379004 N.mm^-3/2

to

0.5782 MN.m^-3/2


...I don't get that. I'm guessing it's the ^-3/2 that's the cause of the number changing rather than just the position of the decimal as it were, but I can't figure out for the life me how.

 

[neodude]

First is in Newton Millimetres.

Second is in Mega Newton Metres.

 

[divine`]

Not strictly, it's Newton Millimetres to the power of negative three over two and Mega Newton Metres to the power of negative three over two.

I have just found buried in an appendix that to convert I need to multiply by 10^-3/2 so now I can do it, though i'd still like a mathematical explanation of why i'm doing that so I understand it better, if anyone knows and can be bothered.

 

[[TR]SweetSpotOz]

You are doing it as that is the conversion factor.

Just like km -> m is multiply by 1000.

 

[divine`]

Ok, so it's just that because it's that, nothing much more to it?

 

[Van_Dammesque]

I have just found buried in an appendix that to convert I need to multiply by 10^-3/2 so now I can do it,

No, you need to divide by that number, mm to m is divide by 1000, so in your case it is divide by 1000^-3/2. (then divide by 10^6 to get it into mega Newtons).


1000^-(3/2) = 3.16^-5

1/(3.16^-5) = 31622 (spooky number, gives the same mantissa when inversed!!)

18.28379004 x 31622 = 578184.2 (/ 10^6)

= 0.5782 MN.m^-3/2

EDIT: OK your way of multiplying is fine, just be wary it converts straight to MN.m^-3/2 !)