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1-Newbie

## I am somewhat new to mathcad but I feel confident in this solve block but it is returning an error. Any help would be greatly appreciated!

As the title says I've been using mathcad for school for about a year and know the basics decently well.  I am working on a thermodynamics problem but I am getting a no solution found error when I try to solve for v1. If anyone could take a look at this and figure out why I'm getting this error it would be greatly appreciated.  I also plugged values into excel to make sure there is indeed a solution and v1 should come out to be something between 200 and 300 m/s.  Thank you so much for any help!

3 REPLIES 3
4-Participant
(To:aholzer)

Hi,

there are a few issues that will need to be addressed before you can expect a suitable answer from tour solve block.

first it only allows for the v.1 variable to change.as written all the other 'variables' will be considered to be constant.

so, taking the equation:

you can rework this to be:

and this gives a single value that will not allow any of the other equations in the solve block to resolve.

one option is to increase the number of variables in the find equation

e.g.

but as you are using units this approach will become very complex as the solve block cannot give results which have differing units as its output.

The outer option that I can think of it to define the dependant variables as functions of v.1 and try rewriting the solve block to use them.

So if C.p is a constant and T.1 is a fixed start condition, then you could write

as

and as here the picture shows the value calculated for t.2 is 336K

without knowing which are fixed & which are variable it is impossible to say much more.

regards

Andy

19-Tanzanite
(To:AndyWesterman)
 one option is to increase the number of variables in the find equation e.g. but as you are using units this approach will become very complex as the solve block cannot give results which have differing units as its output.

Yes, it can. You can't have an in-line evaluation though, and you can't evaluate the vector of results (because of the units mismatch). You can evaluate, and use, the individual results, v1, T2, P2, though.

21-Topaz II
(To:aholzer)

Hi Austin,

Although the problem has not been expressed very clearly, so wanting to find a solution anyway, and reorganizing the whole, I found a simple solution such as the following:

Bye

F.M.

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