## Rigid Rod Dynamics in 2D

From: "andrew cooke" <andrew@...>

Date: Sat, 15 Sep 2007 22:58:25 -0400 (CLT)

Hardly earth-shattering, but I seem to have the physics correct now, and
the collision detection reliable.  Physics error was a stupid confusion
between speed and velocity (duh!) along with some sign errors from
less-than-rigorous maths (it's always always easier to just use vectors,

Image at http://www.acooke.org/cgi/photo.py?start=napito-4

Now I can try generating some interesting images....

Andrew

### Explanation of Picture

From: "andrew cooke" <andrew@...>

Date: Sat, 15 Sep 2007 23:04:03 -0400 (CLT)

I guess it's probably completely unobvious what is happening in the image
in the previous post ( http://www.acooke.org/cgi/photo.py?start=napito-4 )

You can think of it as a "photograph" of three moving "rods", illuminated
by a strobe light.  So you see "trails" of the three rods at slightly
different times.

One rod starts from bottom left moving up, another top left moving down.
They collide twice and then the top left rod collides with a third rod
moving up from the bottom right (actually, I'm not sure about the exact
ordering of the second and third collisions - they appear to be almost
simultaneous).

Andrew