OT: Bush in Free Fall

[Jim Hurley]

>
>Message: 13
>Date: Sat, 22 Oct 2005 09:48:43 -0700
>From: Mark Wieder <mwieder at ahsoftware.net>
>Subject: Re: OT: Bush in Free Fall
>To: How to use Revolution <use-revolution at lists.runrev.com>
>Message-ID: <1121127080.20051022094843 at ahsoftware.net>
>Content-Type: text/plain; charset=us-ascii
>
>Jim-
>
>Friday, October 21, 2005, 5:51:36 PM, you wrote:
>
>>  something else. There is some complicated physics there.
>
>Here's a paper on the free-fall physics behind the animation, although
>it's still beyond me at the moment, although using Verlet integration
>for molecular dynamics does sound appealing:
>
>http://www.gpgstudy.com/gpgiki/GDC%202001%3A%20Advanced%20Character%20Physics
>
>--
>-Mark Wieder
>  mwieder at ahsoftware.net
>

Mark,

I didn't look at the link carefully (actually I scrolled rapidly to 
the bottom of the window) but it may not deal with the specific 
problem faced by the falling Bush, not to be confused with the 
burning bush.

That animated character is physically  equivalent, I think, to a 
series of linked rigid rods. So imagine a set of linked rods and an 
impulse is applied to one of them--when it strikes a ball. You know 
the impulse (technically  the integral of the force over time) is 
normal in direction to the surface of the ball at the point of impact 
(and normal to the rod segment as well) and is of such  a value  that 
it brings the point of impact momentarily to rest--the rod 
momentarily rotates about the point of impact. From this one must 
work out how that impulse affects not just that rod but all linked 
rods. It is a nightmare physics problem. Even the manner in which the 
model slithers over the balls is a work or art and physics.

A  simpler problem would be a single falling rod with an angular 
velocity omega and striking a fixed peg. Determine the subsequent 
motion. Not a simple problem. But imaging a series of linked rods?

Someone has a lot of time on his or her hands.

But, thanks for bringing it up. Shows what a dedicated mind can accomplish.

Jim