I keep waiting for Neil to pipe up and say "For heaven's sake, people, stop guessing. Go to http://www.phunland.com/wiki/Download and start experimenting!" However, when I followed my own advice, I needed to call him up to get started. His lesson was roughly: Click on the Box creation tool. Drag diagonally near the top center of the background to create a fairly wide box. Click on Simulate (rightward triangle). The box should crash to the ground. Click Undo (double leftward triangle). The box should relevitate. Click on the Fixator tool (X). Nail the box to the background. Click on Simulate. Nothing should happen (except clouds drifting.) Click off Air resistance. Create a long, moderately thin vertical box for the pendulum "string". To get a Materials menu, you might need to click on the Move tool (crosshairs). Make the string out of helium or something. Nail it to your overhead box with a Hinge tool. Make a large steel ball with the Circle creation tool. With Materials, set its restitution to 1.0, and its mass to something convenient, e.g. 100kg . It might help to set its friction to 0. Nail it to the lower end of the string. With the simulation running, you can swing it out with the Drag tool (hand) and unclick to release it. Select the hinge-string-nail-ball system with the Polygon tool and Group it (with Select) and Clone it three or four times. Move the groups closer together to minimize offcenter collisions.
This simulator will eagerly model imperfections. When I got the equal mass scene working ideally, I saved it and then doubled the mass of the impactor and saved that, intending to avail the two scenes to math-fun to save you the foregoing setup trouble. But as far as I can tell, the save feature doesn't work on the Mac.
Anyway, the double mass impactor sent the last ball on a large excursion and the penultimate ball on a smaller one.
Phun can presumably well-describe a one dimensional sliding track model, which is the infinite-string limit. --rwg PS, an unfinished paper of Neil's informed me of http://www.chris-j.co.uk/rott.php , which you should check out if you've never seen Rott's pendulum.
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Neil is cheating. He has this amazing physics simulator from http://www.phunland.com/wiki/Home that even models air resistance. The clone feature naturally placed the balls slightly apart, which we deemed a plus, but strangeness ensued! The middle balls soon started moving, then gradually calmed down, then gradually excited again, ...
It turns out to depend on string length! If the strings are short and the gaps are large, the ball collisions are off center. So make the strings really long, and all should be clear. --rwg (Neil wishes to point out that his incorrect answer preceded the software experiment. He may be a poor theoretician but never a poor experimentalist.)