Robert Larson 800-2875 Center Finder

by Dan Posted on April 26, 2011

Neat: (from Make: Online)

If you’ve ever struggled to locate the center of a circular plate or a piece of round stock using a ruler or a square, you know it can be a tricky proposition.

But this cleverly-designed gauge from Robert Larson Woodworking Tools makes short work of the job, and does it more accurately, to boot. Basically, it’s just a small framing square with a built-in 45-degree rule: Fit the workpiece against the square, mark the bisector, rotate it about 90 degrees, and do it again. The lines will intersect right in the center, no matter the exact angle between them, whether you draw two or twenty.

The gauge actually has two sides—one with 90-degree jaws for use on round, square, or octagonal stock, and one with 60-degree jaws for use on hexagons.

Good old angle bisectors. “When are we gonna use this?”

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Math Pics: Underground Carriages

by Dan Posted on April 25, 2011

The following is the first of a few pictures that I took while on spring break in London.

This is a flyer that is talking about the improvements to the London Underground. The Summer Olympics are coming next summer, so they are trying to increase the capacity.

So, how many carriages per train are there now?

and, how many more passengers can they carry per day?

Attached is the full flyer with an easier question to answer with the Waterloo Line of the Underground.

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Giant Gummy Bear #WCYDWT ?

by Dan Posted on April 15, 2011

What questions come to mind? Maybe it’s because it’s the day before spring break, but I’m having trouble coming up with good stuff. Is this worthy of the #wcydwt tag?

from http://www.boingboing.net/2011/04/15/worlds-largest-gummi.html

Features & specs:

  • Dimensions: 9.5″ x 5.5″ x 3.5″
  • Equivalent to 1400 regular-size gummy bears
  • Weighs approximately 5 pounds
  • 12,600 calories!

From: http://www.vat19.com/dvds/worlds-largest-gummy-bear.cfm

The best question I have is “How tall must a normal gummy bear be?”  This question would get to the idea that the original might be 11.2 (the cube root of 1400) times smaller than the large one. This would put the height of the original gummy bear at 9.5″/11.2 ~ 7/8″ of an inch tall. Or do you not tell them the height of the large gummy bear and have them measure a small one and extrapolate?

P.S. Other similar foodstuff: World’s largest gummy worm http://www.vat19.com/dvds/worlds-largest-gummy-worm.cfm

Update: John Scammell blogs about his Giant Gummy Bear experience (great stuff): http://thescamdog.wordpress.com/2011/04/21/the-giant-gummy-bear/

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Möbius Transformations

by Dan Posted on April 6, 2011

From Boing boing and linked article:

Abstraction lies at the heart of mathematics. It makes math powerful, but at the same time, it can make math hard to understand. Abstraction makes math simultaneously beautiful and austere, useful and esoteric.

But a picture can tame the mad monster of abstraction, and sometimes, a video can do so even better. Now, a pair of mathematicians has created a video (see http://www.youtube.com/watch?v=JX3VmDgiFnY) that shows how to visualize and understand Möbius transformations, which are a fundamental and highly abstract mathematical tool. The new video, “Möbius Transformations Revealed,” has become an Internet sensation, with 60,000 hits on YouTube so far. It also won honorable mention in the Science 2007 Science and Engineering Visualization challenge.

Awesome video:

 

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