## Sunday, August 18, 2013

### Help Getting Started with Scratch

I will be teaching a mathematics class this Fall for middle and high school math teachers. The course requires that students do a bit of programming in the Scratch environment. To smooth their entry into Scratch,  I have written three Getting Started with Scratch  documents.
The first document guides the reader through the steps of building a script that draws a square with a side length of 100 steps. This introduces the blocks menu and the mechanics of connecting blocks together to build a script.
The second document describes how to create variables, sliders, and how to set the minimum and maximum values in a slider. The size of the square is now under variable control.
The third document helps the reader build a script that will draw any regular polygon. In a regular polygon the side lengths are equal. A slider controls the number of sides and again, the side length is controlled by a slider.
The relationship between the number of sides and the turn angle for a regular polygon of n sides requires a bit of mathematical analysis.

You may request any or all of these documents—in PDF format— by sending an email .
Getting Started with Scratch - Part 1
Getting Started with Scratch - Part 2
Getting Started with Scratch - Part 3

## Thursday, August 8, 2013

### A Simple Model of Diffusion

This Scratch project is an over-simplified look at the physical process that occurs when a drop of ink is placed in a very thin layer of water.
The ink molecules perform random walks. Over time, the molecules drift from the center and diffuse throughout the water.
In the following short video, I demonstrate how to add a drop of red food coloring to a very thin layer of water and then watch as the coloring diffuses in a near perfect circle. Several billions of red-colored particles are involved in the video and the statistics that govern the random walks of such a large number of particles accounts for the circular diffusion.
The following Scratch project is my first look at 'cloning', available in the new 2.0 version of Scratch. Years ago I did this same project in Starlogo