Serious SI Question

[zdas04]

What is the convention for exponating units with multiple letters? I saw "100 km³" the other day and can't for the life of me figure out if the intent was "100 thousand cubic meters (10⁸L)" or "100 cubic kilometers (10¹⁴L)".

MathCAD says that 100 km³=100 (km)³" but MathCAD treats "km" as a single unit. Is that the official convention or just a MathCAD convention?

In my terms, 100 cubic kilometers is 3.5 TCF and 100,000 cubic meters is 3.5 MMCF.

David

 

[zdas04]

His teacher should have REALLY swatted him for kgf/cm^2. Especially when 1 kgf/cm^2=0.981 bar so what are you gaining?

The class I was teaching last month in South Africa was really interesting. I have a slide describing g_c for converting from lbf to lbm and everyone was glazing over and feeling really superior because SI doesn't have that nonsense. About half way through the slide I asked if anyone had seen gauges calibrated in kg/cm^2 and about half had.

I wrote the Bernoulli equation on the board and asked what happens if you add kg to kgf. At the end of the discussion it was clear that you had to divide kgf by 9.81 or multiply kg times 9.81 to get the same answer we got in kPa, but that 9.81 m/s^2 screwed the units up even more. They were discusted that g_c had arrived for SI and didn't feel quite so superior.

David

 

[SomptingGuy]

centimetres

The hook for a very rude joke on a TV show called "The Young Ones".

Cool guy (Mike) is trying it on with a young lady:

"I know what you're thinking baby and if I told you, you'd think I was talking centimetres."

- Steve

 

[ScottyUK]

Ah, happy days watching that show.


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[KENAT]

Ah young ones, or some of the other offerings by the involved parties.

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[hokie66]

bt,

Yes, of course a cc and a ml are the same thing. I don't know about syringes where you are, but over here, they are all in ml, not cc. And a litre is a cube 100 mm on a side. There...I defined it.

I thing kgf/cm^2 is a French thing. Enough said.

 

[VEBill]

"The nice thing about standards is there are so many from which to choose."
- I'm not sure who said it

 

[btrueblood]

Hokie, I'll have to go check. I've seen devices calibrated both ways, but it may just be memory as the latest stuff I've purchased does state mL.

Steve, I tried to skate a bit farther away from the line by saying "other medical metrics"...

 

[vpl]

VE1BLL

A virtual star for you!

Patricia Lougheed

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[BigInch]

I don't mind kPa, but India uses tonnes/year as flowrate. Ask me how much I like that.

If you buy almost any furniture or household item anywhere outside the US and I promise you'll use cm.

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[zdas04]

[Coming full circle] How about Liberia and Myanmar?

David

 

[patprimmer]

I believe they still use cubits which of course is still useful if you believe global warming will produce another great flood and you therefore wish to build an arc. ;-)

I believe one biblical cubit equals 45.72cm.

I guess the SI purists can convert that to mm with an appropriate conversion factor.

When I build something I normally use a tape or ruler calibrated in inches, cm and mm. Unfortunately I have to do the sums if the drawing is scaled in cubits.

Regards
Pat
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[KENAT]

"I normally use a tape or ruler calibrated in inches, cm and mm"

In which case I'll often use whichever set of units have a 'line' at about the right spot to minimize cutting error. So I have merrily mixed inches and mm on home construction projects before - obviously measuring twice...

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[BigInch]

Well as long as you're not sending missions to Mars, maybe it will work.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso