I need some help

[vmoldovan]

Anybody can tell me what I made wrong ? or what is the problem ?

[Werner_E · Accepted solution]

The error message unfortunately is not helpful at all. It has nothing to do with the units.

The reason you get this error is because you are using the wrong type of index. You are using the vector/matrix index (which you get by typing [) but you should have used the literal index, the subscript which you can get by clicking on subscript in the math ribbon (section "style") and the keyboard shortcut is Ctrl and -

Normal you would get an error telling you that the variable h is unknown and you should get this error in case of q_a. But h is also a predefined constant (type h=  to see which) with units and thats the reason for this misleading error message you got.

WE

[MJG]

I could be mistaken, but I'd guess that Psi.h & Psi.m should actually be unitless resulting in d.2 being a distance (likely a radius given the equation).

[Werner_E]

Mark Gase wrote:

I could be mistaken, but I'd guess that Psi.h & Psi.m should actually be unitless resulting in d.2 being a distance (likely a radius given the equation).

Yes, d_2 sure should be a diameter but I guess that Vlad simply was playing around, exploring the possibilities of Prime on his first or second day after installing the trial Version 😉

[vmoldovan]

Thanks for help. I use Prime only from 2-3 days. I start to learn it for university, and I have much to learn.

[Werner_E]

You are welcome!

Don't hesitate to come back and ask if you experience any other problems

WE

[MJG]

Your subscript "h" is matrix index ([).  You should use a literal subscript (Ctrl -) in this case.  The error shown is because "h" is a predefined constant (Planck's constant) with units and units are not allowed in a matrix index.