units in solve block not working

[jpyland]

Hi, using Mathcad 15.0. I have a solve block producing some very strange units, and I can't get it solve with the right units.  If I take each result out of the Find, the units are right. Anyone know how to get this to work? Mathcad file attached.

[LucMeekes]

You should realise that the symbolic processor of Mathcad doesn't know about units, it treats them as unknown variables at best.

I get this:

Then solve the set of equations symbolically:

This results in a big expression in a matrix with one row, three columns.

Then define the values and calculate:

Check your expressions for the various C- and LF- values.

Success!
Luc

[Werner_E · Accepted solution]

The symbolics does not know anything about units. So it does not know that lbf = lb*s^-2*ft and therefore it can't simplify its results.

I see no reason for using the symbolics as you are only after numeric results.

You already have provided guesses for the three variables, so stay with numeric solutions.

Because your three variables aren't of the same dimension (different units), Mathcad can't display them in one matrix, but you always can assign the result to a vector with separate variables and display them singly:

Mathcad would display the results using just the base units of the chosen unit system and lbf is a derived unit. So just type lbf in the unit placeholder after the displayed result and Mathcad will care for the rest.

[anursingh]

Hi @jpyland,

I wanted to see if you got the help you needed.

If so, please mark the appropriate reply as the Accepted Solution. It will help other members who may have the same question.
Please note that industry experts also review the replies and may eventually accept one of them as solution on your behalf.
Of course, if you have more to share on your issue, please pursue the conversation. 

Thanks,
Anurag