"Unit don't match"

#1 Опубликовано: 10.04.2019 03:54:52

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Hi,

I'm new to SMath. It's a great software but I'm frustrated with an (maybe simple) error.

I try to calculate a density wich follows a simple linear equation:

The equation is: D = 0,0006x+1
x stands for the mass.

Now I try to calculate the density with different masses:

How you see I can't solve the second equation with the unit "g". SMath shows "Unit don't match". I try different ways to insert units but it doesn't work in any direction.
So, what can I do? Where is the failure?

Thanks in advance for your help!

#2 Опубликовано: 10.04.2019 05:15:04

sergio

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The formulation you wrote for the density calculation (linear equation) would suggest a dimensionless formulation (those typical equations contained in technical manuals or codes). Therefore it must be used in dimensionless form with the quantities inserted without a unit of measurement. With m2 you have instead used a unit of measurement that caused the error by not being able to add up a dimensionless quantity (1) with a quantity with unit of measure (g)
sergio

#3 Опубликовано: 10.04.2019 05:24:13

MR

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Thank you for quick reply!

I will calculate it dimensionless.

#4 Опубликовано: 10.04.2019 05:32:30

Davide Carpi

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The 2 typical approaches; as said by Sergio the dimensionless operand drives the result:

https://en.smath.com/cloud/worksheet/3ecekeDo

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#5 Опубликовано: 10.04.2019 10:57:16

Jean Giraud

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So, what can I do?

... work Engineering/Scientific projects Unitless
Maths are unitless, so projects using maths.
IMHO, the attached is a good example.

Inst_Colebrook Pipe Data.sm (59 КиБ) скачан 41 раз(а).

#6 Опубликовано: 11.04.2019 02:49:20

MR

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Thanks for all answers!

#7 Опубликовано: 11.04.2019 09:47:40

Jean Giraud

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Thanks for all answers!

Knowing in what units the document is designed/produced,
you can always append the unit in the result ... like this:
you can't define kg/m³:=1
otherwise kg_m³:=1

This SS 6179 should work in your latest SS version.
Cheers ... Jean

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"Unit don't match" - If I insert a unit SMath shows "Unit don't match" - Сообщения