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this is not a valid constraint. for example use the equal to operator

DV_9225506
3-Visitor

this is not a valid constraint. for example use the equal to operator

DV_9225506_0-1653148465126.png

Hi, i am doing some calculations on a project and am quite new to Mathcad. When using the solve block i keep on getting an error and i dont know how to solve this one. Any idea where i might be wrong?

 

1 ACCEPTED SOLUTION

Accepted Solutions
LucMeekes
23-Emerald II
(To:DV_9225506)

Check your equations!

You have 5 equations, and want to solve for only 3 variables. Normally you have 3 (independent) equations to solve for 3 variables.

If I take just the first 3 equations, those in moments, and solve them I get:

LucMeekes_0-1653251585998.png

This is the symbolic solution, which can be found.

Then I try to evaluate it numerically, I get:

LucMeekes_1-1653251651018.png

(Complaint that sol is undefined). On closer inspection the first 2 items have this is the numerator:

LucMeekes_2-1653251702116.png

Which, upon numeric evaluation yields:

LucMeekes_3-1653251726605.png

And that's exactly zero because:

LucMeekes_4-1653252189177.png

So you get a division by 0. Hence Prime judges sol to be undefined.

And also Prime indicates the solve block cannot be solved.

The two extra constraints in your solve block will not help to remedy this problem.

 

However, if I remove the first two constraints, I get this result:

LucMeekes_0-1653252660524.png

 

Check your equations.

 

Success!
Luc

View solution in original post

5 REPLIES 5

My first observation is that many of your constraints are not unit consistent; you mix terms of force (N} with moment (N m).  Fix that, see if it helps.

 

Attaching the file would help too!

This is the part where i am stuck, unfortunately i cant upload the whole document

 

LucMeekes
23-Emerald II
(To:DV_9225506)

Check your equations!

You have 5 equations, and want to solve for only 3 variables. Normally you have 3 (independent) equations to solve for 3 variables.

If I take just the first 3 equations, those in moments, and solve them I get:

LucMeekes_0-1653251585998.png

This is the symbolic solution, which can be found.

Then I try to evaluate it numerically, I get:

LucMeekes_1-1653251651018.png

(Complaint that sol is undefined). On closer inspection the first 2 items have this is the numerator:

LucMeekes_2-1653251702116.png

Which, upon numeric evaluation yields:

LucMeekes_3-1653251726605.png

And that's exactly zero because:

LucMeekes_4-1653252189177.png

So you get a division by 0. Hence Prime judges sol to be undefined.

And also Prime indicates the solve block cannot be solved.

The two extra constraints in your solve block will not help to remedy this problem.

 

However, if I remove the first two constraints, I get this result:

LucMeekes_0-1653252660524.png

 

Check your equations.

 

Success!
Luc

Thank you so much for your help.

Hi,

Can you please upload the worksheet?

Cheers

Terry

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