Incorrect Unit calculation

#1 Posted: 1/31/2015 11:11:42 PM

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Group: User

Hi all,
some problem which unit calculation

K:8.87
α:1
β:0.43
γ:0
b:200*'мм

Kα:K*(α+(β*{α^2}/{b^2})+(γ*{α^4}/{b^4}))^0.5=#

result: Unit does not match((((

#2 Posted: 2/1/2015 9:39:04 AM

Davide Carpi

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The error seems correct. Just make a dimensional analysis on α+(β*{α^2}/{b^2})+(γ*{α^4}/{b^4})

You sum something dimensionless with 1/мм^2 and 1/мм^4

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#3 Posted: 2/2/2015 7:45:39 PM

nik

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Wrote
The error seems correct. Just make a dimensional analysis on α+(β*{α^2}/{b^2})+(γ*{α^4}/{b^4})

You sum something dimensionless with 1/мм^2 and 1/мм^4

I`m not convert unit of measure, math operation only value. mm^4 you real?? what a dimension, square? cube or astral?

#4 Posted: 2/2/2015 8:11:26 PM

Davide Carpi

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Maybe the attached picture helps a little bit more to understand the issue...

As stated previously, you can't sum apples and oranges; therefore the error message seems consistent...

2015-02-02 23_58_30-SMath Studio Desktop - [Page1_].png

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#5 Posted: 2/3/2015 6:46:44 PM

nik

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ок,

???

formula

#6 Posted: 2/3/2015 7:20:22 PM

Davide Carpi

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Thanks for sharing the original formula, this makes more sense; seems you have missed or merged a parameter (alpha) with a variable (a)

Best regards,

Davide

nik.sm (17 KiB) downloaded 40 time(s).

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#7 Posted: 2/4/2015 6:04:59 PM

nik

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this is font trouble, real value "a"

#8 Posted: 2/4/2015 7:20:46 PM

Davide Carpi

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Group: Moderator

Seems strange, because in this way the formula has both mathematical sense (alpha*x^0+beta*x^2+gamma*x^4) and physical sense (homogenous units involved in the calculation)... there is some literature about this formula? (where it is used? has an author?)

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