29 April 2013

The "Snail Ball" rolls s--l--o--w--l--y downhill

From Grand Illusions, via Nothing to do with Arbroath.  The physics behind this phenomenon is explained in an article (pdf) at Mathematics Magazine, and nonmathematically summarized below this fold...

"...inside the ball, which is actually hollow, there is a viscous liquid and a smaller ball which is very heavy. When the Snail Ball rolls slowly down an incline, it is the smaller, heavier ball inside that determines the pace, and this is slow because of the viscous liquid..."


  1. I've made these in the past. You take a hollow ball and fill it part way with honey. Then, you place a pinball inside and seal the hollow ball. Place it on an incline, and the honey inside slows the progression of the ball rolling down the incline.

    We used plastic ornament shells, where you put the two half-domes of plastic together to make the shell of an ornament, then paint it on the outside so it looks solid.

  2. And we did it for a science experiment based church school curriculum. The kids loved it almost as much as the Mentos + Diet Coke experiment!


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