# IntMath Newsletter: Pulleys, Teraplot, primes

By Murray Bourne, 02 May 2014

2 May 2014

In this Newsletter:

1. Pulleys interactive applet: math background

2. Resource: Teraplot LT

3. Math puzzles

4. Friday math movie: Falling in love with primes

5. Final thought - producer or consumer?

## 1. Pulleys interactive applet: math background

I recently updated the pulley applet on IntMath. There was a lot of interesting math involved, and here's a description of it: Pulleys interactive applet: math background A lot of the same math is used when writing computer games. |

## 2. Resource: Teraplot LT

Teraplot LT is a free 2D and 3D graph plotter for Windows 8 and Windows-based tablets. It's the scaled down version of the fully fledged Teraplot Graphing Software (which is a commercial product. They have a free 30 day trial). I enjoyed working with both products and found the output quality is quite good. |

## 3. Math puzzles

The puzzle in the last IntMath Newsletter asked about solutions for an inequality.

Correct answers with explanation were given by Peter (who provided 2 different approaches), Emily, Tomas, Francis, Nicos, Cichy and John.

(Some people just sent a number only as their answer. There was no indication of the thinking behind their conclusion.)

**New math puzzle**

Let's revisit the pulley applet. As explained in the article mentioned earlier, for the applet to look right, we need to know where the segments intersect with the circles.

The new puzzle is: Given 2 pulley wheels of different radius *r*_{1} and *r*_{2}, with centers that are distance *d* apart, find the point where the first circle intersects with the segment joining the 2 circles. (The segment is tangent to each circle, and the left hand circle is centered at (0,0).) That is, you need to find the point where the red dot is.

Leave your responses here.

[**Hint:** If you want to enter subscripts in your answer, do it like this: r<sub>1</sub>. This will come out like this: r_{1}. If that's too troublesome, just put r1. We'll understand!]

## 4. Friday math movie: Falling in love with primes

Comedian Adam Spencer gives us the lowdown on finding monster prime numbers. |

## 5. Final thought: producer or consumer?

As mentioned earlier, reader Peter gave 2 responses to the math puzzle. In a separate comment, he said:

My first response was done on an iPad. I find it hard to be wordy on that medium. The second was done on my computer with a full keyboard. That would be an interesting survey question: Are you more thoughtful (and complete) when providing an answer on a smartphone, tablet, computer, or pen and paper?

I've often thought about this. I use my phone and tablet for consuming content 95% of the time. They are good for that, but certainly not good for creating serious content, especially if it involves images and several other technologies (which my writing nearly always does.) I'll usually only respond to emails (or most other things) when I get home.

The other thing I've thought about is that as fewer people buy and use desktops and laptops, and move to mobile devices, it will mean less creators and more consumers. This is actually not good for our future.

What do you think? Please respond here.

Until next time, enjoy whatever you learn.

See the 11 Comments below.