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Cannot solve a matrix equation with the Maxima plug-in
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Hi, I'd like to solve the following equation involving matrices for unknown v and θ:  After inputting it in the format used by the Maxima plug-in I get the "no result" message:  Am I doing something wrong ?  Matrix equation.sm (9kb) downloaded 14 time(s).
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Originally Posted by: EngMath  Am I doing something wrong ? Your setup is not correct. 
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I think the problem is that the units don't match. Compare the units of the components of the two terms inside the brackets that multiply the [v; theta] vector.
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Originally Posted by: StvMath I think the problem is that the units don't match.
Compare the units of the components of the two terms inside the brackets
that multiply the [v; theta] vector.
FindRoots ignores Units. Code the image first. Solve FindRoots Complex Forum.sm (12kb) downloaded 3 time(s).
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Originally Posted by: Jean Giraud Your setup is not correct. Thank you, I didn't know that I should use the Nonlinear Solvers plug-in instead of the Maxima one. It works now but the result is surprising. It should be something like v = - 0.021020 for the real part with this input data. Originally Posted by: StvMath
I think the problem is that the units don't match. Compare the units of the components of the two terms inside the brackets that multiply the [v; theta] vector.
I also suspected the units initially but it didn't work without them either.
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I also suspected the units initially but it didn't work without them either.
In order to be able to add the two terms they must have the same units. However, omega^2*L doesn't have the same units as EI/L^3. The omega^2*... term seems to be missing a linear mass density (kg/m).
The fact that you might be able to get a numerical result by simply removing the units is irrelevant.Edited by user 13 June 2023 17:20:06(UTC)
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Joined: 18/10/2020(UTC) Posts: 50
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Originally Posted by: StvMath
In order to be able to add the two terms they must have the same units. However, omega^2*L doesn't have the same units as EI/L^3. The omega^2*... term seems to be missing a linear mass density (kg/m).
The fact that you might be able to get a numerical result by simply removing the units is irrelevant.
Right, I was wondering why density/mass is not included in that equation. Especially since it's included in the equation for tension (the one here is for bending): https://code-aster.org/V...n/man_v/v2/v2.06.101.pdfMaybe it's a typo and the density should be added before the first omega. Or omega means something different than I assumed (angular frequency). Edit: I tried calculating mass per unit length based on the density and cross-section area provided in the document and then multiplying it by omega^2 but the result is v = 0,0175 which is still far from the expected value. Edited by user 13 June 2023 21:21:32(UTC)
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Besides correction of the unit mismatch, Solve seems to want the matrix equation in homogeneous form.  Matrix equation_Kr.sm (15kb) downloaded 5 time(s). |
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Hi. Another way.  Best regards. Alvaro.
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