Posts tagged ‘math’
Pendulum patterns
May 13th, 2011 at 10:47 pm by Dr. Drang
It was on Boing Boing and Kottke, so I’m sure you’ve seen this video of 15 tuned pendulums. The pendulum lengths are set so longest pendulum swings through 51 cycles per minute, the second-longest 52 cycles per minute, and so on up through 65 cycles per minute. As we showed in this post a couple…
The unreasonable effectiveness of mathematics
March 27th, 2011 at 2:25 am by Dr. Drang
My family and I are on vacation in Maui. There was a contest on the flight here from SFO a couple of days ago: Guess the exact time (to the nearest second) at which the plane would reach the halfway point of the trip. The crew gave out a lot of information about airspeed, distance,…
Oil can what?
February 12th, 2011 at 3:38 pm by Dr. Drang
I’ve been working on a nonlinear finite element program for the past week or so, and to shake out the bugs, I run it on a few test problems. One of my favorites is an example of snap-through buckling. It’s a simple little toggle structure with surprisingly rich behavior. The toggle looks like this: Two…
Coke cans, pull-tabs, and the class struggle
January 8th, 2011 at 3:45 pm by Dr. Drang
Yesterday, my wife sent me a link to this video. Bill Hammack, the self-styled Engineer Guy, has several cute videos like this posted on his web site, his YouTube channel, and his Facebook page. I think I saw one of them—the one where he takes a copier apart—on Boing Boing many months ago. Hammack’s an…
Fraction arithmetic practice sheet
January 6th, 2011 at 10:03 pm by Dr. Drang
The next logical step after yesterday’s worksheet for reducing fractions is one for adding and subtracting fractions. The rules for using it are the same as my other math practice sheets: A new set of problems is generated every time you open or Refresh/Reload the page. You can use the version online or save a…
Fraction practice sheet
January 5th, 2011 at 10:57 pm by Dr. Drang
I had a long drive today, and I passed the time by thinking about making a new set of math practice sheets for my ten-year-old son. This year has been fraction-heavy, so I thought I’d start with a simple one: a page with a bunch of proper fractions that may or may not need to…
A small request
December 19th, 2010 at 6:18 pm by Dr. Drang
I’ve been having a discussion on the MathJax mailing list about which fonts get used to render equations. According to the MathJax font help page, the STIX fonts are supposed to be used if you have them on your local computer. I do have the STIX fonts installed on both my iMac and my Macbook…
MathJax, Markdown, and Instapaper
November 24th, 2010 at 9:36 pm by Dr. Drang
Last month, I got an email from reader and occasional commenter Alan Schmitt who told me that my posts with equations didn’t display well in Instapaper. The problem was that an equation like1 [\Phi(x) = \frac{1}{\sqrt{2\pi}} \int_{-\infty}^x e^{-\xi^2/2} d\xi] would appear in Instapaper as [math] which, while true, isn’t very informative. I dashed off a…
And now it’s all MathJax
September 23rd, 2010 at 10:50 pm by Dr. Drang
A few days ago, I switched the blog’s equation handling library from jsMath to MathJax. In general, I would say the transition went very smoothly, but there are a couple of oddities I’ve found and also some things I can’t test for. The primary advantage of MathJax is that it uses webfonts for the equations,…
Clock practice for kids update
July 19th, 2010 at 11:00 am by Dr. Drang
For reasons I can’t explain, my original post on printing time/clock practice sheets for kids always forced you to download a zipped archive of files to your local computer, unzip them in some convenient place, and launch them from your hard drive. While this is no burden to my geekier readers (who might prefer a…
