Problem Static

[malmeida2019]

Good afternoon group friends, I am a beginner in Mathcad, and I am not able to finish a static problem, if you can help me, thank you very much.

[Fred_Kohlhepp]

Welcome to Mathcad.

Due to PTC's greed, since you are using Prime version 5, many of us cannot see your problem.  Consider posting a picture version as well.

[malmeida2019]

ok

[malmeida2019]

Follow the file in jpg

[Werner_E · Accepted solution]

What did you expect? You have not defined x and y so you cannot expect a numeric result.

You may let Prime evaluate symbolically, though.

[malmeida2019]

Werner, why the final answer did not show in "m", what I'm missing here. If you had to solve this problem through vectors would you do the same thing I did?

[LucMeekes]

That is due to your definition. You defined rp as rp:=[x y 0] m. This means that x and y, like 0 are just numbers, without units. I would be rp that contains x m, y m and 0 m.

If you're interested, you might try to find out what happens if you define rp as rp:=[x y 0] and then solve x and y.

Success!
Luc

[malmeida2019]

Thanks LucMeekes, but I did not quite understand the answer, rp = [x y 0] m is different from rp = [xm ym 0m]. I used it the way it said and it did not work, could you please give a practical example.

[Fred_Kohlhepp]

Attached is Prime 4 file, readable with 5

[malmeida2019]

Thank you Fred that's what I needed, clear and perfect explanation.

[rgunwaldsen]

Sorry to nit-pick, but I think Fred has a sign error.

[rgunwaldsen]

Sorry, Prime 5 worksheet. PDF attached.

[Fred_Kohlhepp]

Thanks for pointing out my error!  (See the attached sheet for a long, devious correction and reason.)

But your solution also has an error:  cross products are sensitive to order; both your solve block and your check have the order reversed

should be [-0.114   0.2   0]

[rgunwaldsen]

You're right, as usual, Fred. I need to go back to school!

[Fred_Kohlhepp]

I ALWAYS have to check. . .