problem with my units

[alanmardan]

Dear all,

I have problems with different things on my Mathcad15.

1. when i create equations based on defined variables, the units are not as expected when i enter the unit i want to be as my result unit.

2. when i go to help search, the menu is disabled and only numbers appear insted. but when i press the numbers i get a message that i could have problem with active ontroll function.

3. how can i get the my result from an equation as unitless? the variables are defined with units above

i really need help with this as i have to submitt my course work very soon.

regards

Alan Mardan

[ValeryOchkov]

Attach please the file!

[alanmardan]

Hi Valery, thanks for the respond

I have highlighted some of the equations and explained what unit i want the results to have. the two main problems are:

1. I can not get a unitless result using my defined variabes which have units

2. some of my equations give me units in kg per something, but all my units are based on either kN/m, kN, m, mm and kNm (For civil engineering)

sorry if my calcs are messy but tried to highlight some of the problems in yellow

looking to hearing from you

Thanks

Alan

[ValeryOchkov]

Do not change values of variables m, N etc. They are units - meter, newton etc

See my red operators in the attached file!

This promlem is solved in Mathcad Prime!

[alanmardan]

Would you please explain me because i can't understant why you highlight the coefficients, the are only unitless coefficients. And also, how to get some equations unitless. thanks

regards

alan

[ValeryOchkov · Accepted solution]

I would like to show you that you change the value of the variable m and later use mot meter (m) but you user variable m that is mot yet meter.

[alanmardan]

Hi Valery,

Thank yo very much for the help, i just didn't think bout it as i am new to mathcad. thanks

Regards

Alan

[MikeArmstrong]

1. I can not get a unitless result using my defined variabes which have units

Why would you want to get a unitless result?

Mike

[alanmardan]

Hi mike,

I think my problem is solved so far, i had used an equation called 'm', which changed the value of my meter unit to the equation result, because i use kNm.

Thanks anyway

[PhilipOakley]

Given your point 2. I would suggest that you have an installation problem.

If you open the tutoriuals at one of the units examples, does it give the same problem. Use the address toolbar in the resource centre window to find its true location, and then open directly in the main mathcad to avoid differences between the resource centre execution and user sheet execution.

Good luck.

Philip

[alanmardan]

Hi philips,

I had a virus on my computer and started to remove things from internet explorer as the virus stopped my antivirus from workin. So i removed things from explorer and i think some thing wrong went in between there.

regards

Alan

[mzeftel]

Alan,

Go to add/remove programs and repair Mathcad. That should help if you accidentally uninstalled something.

Mona

[alanmardan]

I did that also, a pop up appears '' the feature you are trying to use is on a network resource that is unavailable'', i even tried to enter the instalation DVD to locate the path to repair it from there but it didnt work.

I dont knot whther my existing password would work if i reinstall the program, as i have no time to wait for new activation keys due to my coursework deadlines.

Thank you any way

Regards

Alan Mardan

[SamuelCrabtree]

I'm also having a problem with units.I am solving two equations with two unknowns symbolically. The results come out looking like this:

-(15 digit number) x lb x -(15 digit number) x ft^2 + (15 digit number) x in^2

ft^2

If I then copy that complicated expression and type '=' after it mathcad does the reduction and puts out the correct answer, in pounds, to four significant figures like I have directed. But why doesn't mathcad reduce all those ft and in and come out with the correct answer directly?

[ValeryOchkov]

The symbol Math of Mathcad does not Know what it is units - 100 cm=1m 1000 gm=1kg etc.

Send your sheet and we will try to help you.

[SamuelCrabtree]

I think I now understand.But in case you can show me a better way to solve simultaneous equations I have attached my entire worksheet. I have had the same thing happen on page 2 twice, and page 3 once. In the "(15 digit number)" in my original post the "15" was only approximate.

[RichardJ]

See the attached

Edit: I just updated the worksheet.

[StuartBruff]

Richard Jackson wrote:

See the attached

Edit: I just updated the worksheet.

This is sooo annoying - you posted < 2 minutes before me. All that type-type-typing, click-click-clicking for nothing!

Actually, what is annoying is that I've only got M13 at work and a lot of the recent worksheets have been M14 or M15.

Stuart

[RichardJ]

This is sooo annoying - you posted < 2 minutes before me. All that type-type-typing, click-click-clicking for nothing!

Actually, what is annoying is that I've only got M13 at work and a lot of the recent worksheets have been M14 or M15.

Sorry. I usually save back to 11 before posting, but sometimes I feel lazy.

[StuartBruff]

Samuel Crabtree wrote:

I think I now understand.But in case you can show me a better way to solve simultaneous equations I have attached my entire worksheet. I have had the same thing happen on page 2 twice, and page 3 once. In the "(15 digit number)" in my original post the "15" was only approximate.

There are several ways of tackling this. An important fact to note is that you can assign symbolic results to variables and get a 'standard' display if you press '='. In addition, you could assign the symbolic result to a function - best done before you define any variables to prevent their fixed values being picked up by the function definition. A further solution is to use a Solve Block, which takes a set of conditions and uses numeric (or symbolic) methods to find a solution to those conditions. See attached.

Stuart

[RichardJ]

The symbolic processor does not know anything about units. The variables lb, ft, in are just undefined variables, like any other undefined variable. Only the numeric processor understands units.

It's best to avoid copy and paste, which can easily lead to errors. You can assign the result of a symbolic evaluation directly to a variable, and then evaluate the variable.