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A traditional Newton's cradle involves balls falling under the influence of gravity which exert force in a straight line. Imagine, though, a device which consists of a central axle from which a number of paired, strong and very rigid wires radiate, meeting and terminating in heavy metallic balls. The
whole arrangement rotates about the axle, and the balls are pulled outwards by inertia. The whole arrangement is very large, perhaps several hundred metres in diameter, and therefore can rotate relatively slowly and still generate enough inertia for the balls to be arranged in an arc. It needs to rotate slowly so that one or more balls can be moved from its position by motors on the hub, and allowed to move freely towards the others in order to impact them.
What i'm trying to describe is a circular Newton's cradle.
[jurist, Feb 01 2006]
Mexican-Waving Newton Balls
A conceptually related, but perhaps slightly smaller and more elegant idea from [Farmer John] in 2003. Be sure to view his illustration, and note that he has left the supporting struts out of the schematic for visual clarity. [jurist, Feb 01 2006, last modified Feb 02 2006]
[FarmerJohn]'s Newton's Clock Idea
[jurist, Feb 02 2006]
Lots and lots of clocks... [DesertFox, Feb 02 2006]
Arabian Wheel (or Overbalanced Wheel)
As referenced by [shapu]. Neato animations, too. [jurist, Feb 02 2006]
||I'd keep the whole thing small as Newton's
cradle doesn't scale well. As you increase
the size of the balls, the forces go up and
you the collisions become less elastic.
||I know this is ridiculously huge, but if it were small and relied on rotation, it would have to rotate so fast that what it was doing wouldn't be visible. Also, i thought more massive balls would have more momentum and therefore air resistance would be less of a problem. A possible alternative would be to have the whole arrangement in an evacuated transparent chamber. The smaller Newton's cradles seem to succumb to entropy much faster than the larger ones, but i don't know why.
I would certainly like to scale it down. What about either a rim consisting of magnets (or maybe electromagnets to allow the balls to be moved by the rim rather than a motor) or connecting the axle to a Van Der Graaf generator and using static electricity to pull or push them outward? I think magnets would tend to magnetise the balls themselves after a while, making them stick, whereas static electricity would cause them to repel each other.
[Farmer John]'s idea is pretty groovy, isn't it? There should always be a Moebius Strip involved in a Halfbakery idea, i feel.
||If you enjoyed that idea, you might also like [FarmerJohn]'s Newton's Clock idea.
||[Farmer John] seems to have several neat clock ideas actually, such as that hourglass thing and so on.
||//several// That's an understatement.
||Sounds like an Arabian Wheel to me.
||I see what you mean, [shapu], but the balls would be sticking out at right angles to the centre, and it's not meant to be a perpetual motion machine, because of course "in this house we obey the laws of thermodynamics!"
||Amazing link, [jurist]! I almost feel like i could spend as much time on that site as i do here.