Get Help

Turn on suggestions

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

- Community
- :
- PTC Mathcad
- :
- PTC Mathcad
- :
- Odesolve failure - Kenneth Macfarlane

Options

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

07-14-2014
10:23 AM

07-14-2014
10:23 AM

Odesolve failure - Kenneth Macfarlane

See attached.

Alan

Labels:

9 REPLIES 9

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

07-14-2014
11:38 AM

07-14-2014
11:38 AM

Re: Odesolve failure - Kenneth Macfarlane

Ace. How did you learn this?

Ken

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

07-14-2014
11:51 AM

07-14-2014
11:51 AM

Re: Odesolve failure - Kenneth Macfarlane

Trial and error mostly!!

Alan

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

07-18-2014
08:15 AM

07-18-2014
08:15 AM

Re: Odesolve failure - Kenneth Macfarlane

Alan

I used Mathcad (thanks to you) trying to obtain confirmation of my results from theory according to Dynamics, by J.L. Meriam, and another source from an internet search. Both the theoretical resutls match each other using different equations, but Mathcad gives different answers (see attached worksheet). Any views on this?

Ken

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

07-18-2014
09:48 AM

07-18-2014
09:48 AM

Re: Odesolve failure - Kenneth Macfarlane

I can't see anything wrong with the Mathcad calculations. I've tried it a couple of other different ways (as two simultaneous first-order equations for y and v, for example, and even as a simple Euler integration!) and get the same solutions. I don't know how the text book authors got their results, so it's difficult to comment. My best guess is that there is a difference in the input data somewhere, but I don't have the book data to check.

Alan

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

07-21-2014
05:47 AM

07-21-2014
05:47 AM

Re: Odesolve failure - Kenneth Macfarlane

Alan

Dynamics, 7th edition, is available as a free download using the following link:

http://www.ebooksdownloadz.com/2014/01/engineering-mechanics-dynamics-7th.html

Ken

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

07-21-2014
09:35 AM

07-21-2014
09:35 AM

Re: Odesolve failure - Kenneth Macfarlane

I've looked at this now, and although page 602 gives the ODE, I can't see either the data you've used or the graphs you included in the worksheet!

Alan

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

07-22-2014
03:23 AM

07-22-2014
03:23 AM

Re: Odesolve failure - Kenneth Macfarlane

Alan

I used a lot of graphite and scrap paper to work this one out. You'll find Sample Problem 8/2 on page 592 useful, together with equations (8/20), (8/21), (8/22), and the damped natural frequency on page 590. Hope you get the same answers.

Ken

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

07-22-2014
10:22 AM

07-22-2014
10:22 AM

Re: Odesolve failure - Kenneth Macfarlane

Using your data and the equations in the text book I get the same results as Mathcad's ODE solver - see the lower section of the attached worksheet.

Alan

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Notify Moderator

07-22-2014
11:34 AM

07-22-2014
11:34 AM

Re: Odesolve failure - Kenneth Macfarlane

Alan

I've realised that the Odesolve_Test file I sent on 18 July had a different spring stiffness from the results I added on 21 July. I reconciled this on the attached updated version of Odesolve_Testb. x(t=.011)'s now match exactly. On my chart 0.4918 is the maximum velocity in the range 0 < t <.011 which of course doesn't match your v(t=.011), but my v(t=.011) is now a perfect match. You've boosted my confidence big time in my results, and for using Mathcad as an alternative. Much appreciated.

Ken

Top Tags