Differential Models

[OscarJ.]

Good morning,

I am reading an excellent book regarding differential models: "Differential Models: An Introduction with MathCad" (english version, by Alexander Solodov and Valery Ochkov). Even if I have been working with MathCad for several years and I have developped a good undesrtanding of programing and other software capabilities, I have no experience with differential models and that's why I start practicing with all the examples I found in this book.

The question: I having some troubles with one of the examples, the movement of water drop in air by gravity and resistance force. I tried to follow, step by step, all the calculation shown in the book, but for some reason I didn't get the same answer. I would appreciate if someone can take a look at it an point me out what I am doing wrong.

I am including whit the worksheet a few images of the example, so you can compare the original information provided.

Thanks a lot,

Lij.

[Werner_E · Accepted solution]

You had setup the range variable for tau with 0.01 .. tau.end+0.1

That way you have a (far too large) step width of 1 - in fact you just graph two points and thats why you get a straight line. In the book you misinterpreted the comma as dot and overlooked the dot.

The correct range for tau given in the book is 0, 0.1 .. tau.end+0.1 (a step width of 0.1)

P.S.: I don't know the book but I wonder if the publisher doesn't offer a download link for all the files used in the book. At least thats quite common nowadays and would make sense.

One author of the book, Valery Ochkov, is around here in this forum. Maybe he can help you avoiding to retype all the sheets. On the other hand, learning effect may be better if the sheet has to be retyped, though 😉

[ValeryOchkov]

Thanks for the interesting on the book.

You can download worksheets of the book here http://twt.mpei.ac.ru/ochkov/work2_eng.htm

And welcome to others models with animation:

http://communities.ptc.com/groups/dynamic-models-in-mathcad

Alexander and me have a plan to publish a new version of the book based on Mathcad Prime.

[ValeryOchkov]

Alexander and me have a plan to publish a new version of the book based on Mathcad Prime.

We can work with units in Prime:

[OscarJ.]

Good morning,

Thank you Valery and Werner for your reply. Very helpful.

Regards,

Oscar J.