The Physics of Colliding Balls

by vha3 on 9/27/2024, 12:41:49 PM with 21 comments

  • by sebtron on 9/30/2024, 2:03:47 PM

    If you are interested in this topic, the author of pooltool[1], a billiards simulator, has a nice blog series about it [2].

    [1] https://github.com/ekiefl/pooltool

    [2] https://ekiefl.github.io/projects/pooltool/

  • by angry_moose on 9/30/2024, 7:10:31 PM

    Also see the (somewhat legendary) "Perfectly centered break of a perfectly aligned pool ball rack" answer:

    https://mathoverflow.net/a/156407

    (updated link to original, not the repost)

  • by IanKerr on 9/30/2024, 5:49:13 PM

    For an interesting exploration of how even the simple physics of two blocks hitting one another can lead to surprising conclusions, I'd highly recommend this 3Blue1Brown video called "Why do colliding blocks compute pi?": https://www.youtube.com/watch?v=jsYwFizhncE

  • by chkas on 9/30/2024, 8:30:49 PM

    I have programmed a small simulation of colliding balls in 2D.

    https://easylang.online/show/#cod=jVPbbptAEH3frzhSpMqJFYppI0...

  • by pontifier on 10/1/2024, 5:03:23 AM

    It took me quite a while to understand exactly what was happening with a Newtons Cradle toy. You know the one with the clacky balls that swing...

    If you hold 2 balls up, and let them fall, 2 balls swing up on the other side. How does it know how many you swung??? It boggled my mind for the longest time. Then I got to playing with one, and found something interesting. It doesn't always seem to work!

    If the balls are perfectly aligned, and touching each other, the effect is dampened by the multi-body collision. It's strongest when the balls are just barely not touching.

    What we see as multiple balls swinging and hitting is really a whole bunch of individual 2 body collisions that are close enough in time to seem like they are a single event.

    I could be wrong about the reason, but this was my observation.

  • by TheRealPomax on 9/30/2024, 4:35:34 PM

    While rare events, it would be lovely if this also included notes on how to deal with "more than two balls" simultaneous contact cases.

  • by amai on 10/1/2024, 7:32:27 PM

    Classical mechanics is easy. Make the same calculations using relativistic mechanics for some real fun.

  • by kookamamie on 9/30/2024, 4:11:46 PM

    A very nice article. I noticed a small typo: "resitution".

  • by kazinator on 9/30/2024, 2:38:56 PM

    Unfortunately, this writeup doesn't mention any words like "spin" or "rotation" or "angular", not even to disclaim that those aspects are not presently being addressed. It looks like a great resource for kids in grade 11 or 12 physics.

  • by anthk on 9/30/2024, 7:01:05 PM

    Koules was cool.