All posts by tutorpaul

Trouble logging in and new communication alternative


I've just learned that many of you were having issues logging in for quite some time now! I'm deeply sorry that A) this outage happened, and B) that it took me more than two months to find out about it. As it turns out I hate email, and I have more than enough of them to deal with at work; it isn't a great excuse but it is my justification for being neglectful of my responsibility to my students. My apologies.

At around the time that the first reports from students came it I was notified by my hosting company that the site was being attacked by "malicious bots", and that they had taken some measures to protect the site and its users. It is possible that they inadvertently blocked access for all of you as well. I have been able to log in both as myself and as a test user, so at this point I'm pretty sure that the issue has passed.

Obviously cannot guarantee 100% uptime for this site, but I would like to do better at knowing when issues and outages creep up. In order to streamline communication, and to hopefully build a strong community of current and former dynamics students which might be willing to help their peers (in the spirit of this site) I've set up a Discord server! Join us: (for the uninitiated, Discord is an online chat platform targeted toward gaming, but it is pretty excellent for anything).

On a more technical note, this site uses WordPress which is basically a steaming pile at this point. I chose WordPress because I needed something that could be set up with relative ease and it is what I had worked with. Moreover, having spent such a tremendous amount of effort producing the content left me with little will to learn or build a different system. For some time now I've wanted to redo this site in Django (and change my hosting provider). This is a call for any developers and/or designers (or would-be developers and/or designers) who might be interested in contributing to a rebuild [take notice: having a real-world project with actual users generally supersedes GPA considerations in interviews].

New content!

Well kinda.

The solutions to the problems in chapter 4 are a pain in the butt. Solving them with a calculator is boring and forever-taking, and there was no way I was going to do that for all those problems.

Instead, I wrote me some code to solve each of them in a hurry.

I kept this code private initially because I didn't want any students to mis-use it in any way that could be construed as academic dishonesty. It occurs to me only now that basically all of the content here could be used in an academically dishonest way if homework were graded, and that the Internet is rife with such content for those unscrupulous souls willing to pay. However, I cannot prevent you from misusing any tool that you get your hands on; those decisions are for you make.

My goal in creating this site was to make each of you into better students and better future engineers. Knowing how to use and write software to solve the problems you will encounter in your career is immensely important, so I implore you to install Python and SciPy and to run my codes, modify them to suit your own needs and share them with your friends.

Welcome to

Hello students, I'm glad that you are finding your way to my site! I hope that you find it useful in the coming semester.

Please note that when I recorded these solutions the textbook was in its tenth edition. Some students have asked if I'm planning to update the site now that the eleventh edition is out. The answer is no, the reasons for this choice are first practical and second financial.

First the practical; the problems of the eleventh edition are mostly the same as the problems of the tenth edition. There are some new problems, but most are merely shuffled around. With some diligence you can find how the problems correspond between editions. In fact, some students last semester were kind enough to put the updated problem numbers in the comments for many solutions, so that should help you. Moreover I don't have a copy of the eleventh edition to work from.

Second the financial; I released this work into the public domain as a gift to the students of 363. I have paid for hosting this site for two years (so far), and I spent countless unpaid hours recording and editing the solutions. When I uploaded the last of the problems I considered my gift to you complete. In the spirit of reciprocity for my work I put a donation page on this site. Sadly, that donation page has gone unused for the last 3 semesters. That truth is disappointing for me; I never expected to get wealthy from your donations, but I hoped for some expression of gratitude from at least a small fraction of you. This isn't to say that my generosity has dried up--I'll continue to host the site in perpetuity--but that I've not been moved to put more time into content development.

That said, if there are problems that you really want to see done (which aren't already freely available here) you can buy my time in recording solutions, the going rate is $50/hour. Use the contact page to contact me and we will take it from there.

Have a great semester!

Word has gotten out!

Howdy all, I'm happy to say that this site has attracted 108 of you to register since the start of September! I'm really happy that this content is able to draw you all in without me needing to advertise it! Word has even spread to the Qatar campus!

I'm still hoping to get some help with mapping the problem numbers to the new edition, so please feel free to comment when you notice a correlation.

This site is free of charge because I want everybody to be able to learn how to solve these problems regardless of their financial situation. Resources like these shouldn't be limited only to those who have money to spare; however the content here did require a significant investment of time on my end. That said, if you do have some money to spare and you wish to show your appreciation I encourage donations! Also I hope you'll remember me next semester when you are taking 364.

Happy studies!

New Textbook Edition

Hello everybody, it has come to my attention that Dr Childs released the 11th edition of his book. I understand that many of you are probably using that and won't be able to cross-reference the tenth edition problems (that I've solved) to the eleventh edition problems that you are solving.

I haven't purchased a copy of the eleventh edition, so I don't have a good cross-reference either. The workaround for this issue is for one of you (each of you) as you recognize a problem from the 11th edition make a comment on the problem page stating which problem in the 11th edition it is similar to. If we work together on this we can migrate to the new edition with relative ease.

So, if you recognize one of the videos as solving a problem from the 11th edition, please make note of it in the comments. Also, I will take requests for 11th edition problems to consider working.

Welcome new students


If you're reading this post then you are well on your way to succeeding in 363!

I haven't been publicizing this site very well, but I'm expecting many new students will find it anyhow; word does get around. Here you'll find a (relatively) complete solutions manual for Childs' textbook. It is my hope that you will ask questions or suggest corrections in the comments section of any page. Also, I hope that you will think of me when you have questions regarding 363 (or other course) material as I am available for private online tutoring. When you're done with 363 I also provide group help sessions for 364.

Have a good semester,



I haven't posted anything soliciting donations this semester, and as a result I haven't gotten any! [If you have donated or tried to donate please contact me, I genuinely haven't received any.]  Better late than never.

Please donate to this project if you found it useful!

Also, please be aware that I do cover 364 as an online study-group. I'll be sharing more information about that as summer comes to an end!


Hi everbody! I'm glad you have found my site and that you are making good use of it. It looks like there are about 60 or so new members this semester and usage is strong.

It has come to my attention that any emails sent via the contact page have been erroneously redirected to a spam folder, any communication from that page between January 19th and February 28th were lost to the ether; summarily deleted from an unknown mailbox by an uncaring computer. If you tried to contact me during that time I beg forgiveness and promise my vigilance to future attempts.

Lagrange Material Posted


I was inundated with requests for videos covering Lagrange's method of finding equations of motion, so I've generated four new videos to help you prepare for the final exam.

These will likely be the last videos I can do until the new year (when it likely won't matter to you, dear reader). Speaking of next year, many of you will be taking 364 in the spring and I want to let you know that I will be holding LIVE (online) weekly group sessions to aid you in understanding the concepts covered in the homework. If you think you are interested in joining the group please let me know by commenting to this post or sending me an email from the contact page to inform me of your interest.

Now that the end of the semester is upon us I hope that you will remember all the good times we've had together, all the laughter and all the tears. I hope that you will remember fondly the concepts from 363 (because they do pop up right at the beginning of 364), and I hope that you will remember to donate.


Chapter 5 update


Let's start with the numbers from the last exam. Last Thursday was a barn-burner for, the site hosted 26.5 gigs of content for your enlightenment! That is almost double the previous single day record, I am astonished and thrilled by the viewership of this content!

I've just posted a selection of problems from the second half of chapter 5. If there are any problems you wish I would have done please feel free to let me know and I'll try to add them before the final exam. Right now I'm very thankful to be done with video editing for a little while!

I'm also thankful for those of you who have donated already. So far four of you have donated a total of $200. Maybe you'll consider donating as well?