Three Balls Cup - Physics Demonstration

thingiverse

This is a demonstration of a surprising phenomenon. Two billiard balls are placed in the cup. The cup is inverted and a third billiard ball is placed on top. The system is in static equilibrium until the top ball is removed. Then the cup will do something surprising. The radius of the cup is 1.5 times the radius of the billiard balls. Homework Problem: Calculate the minimum mass of the ball on top required to keep the system in balance. Provide your answer in terms of the fractional mass of a single billiard ball. Designed on Tinkercad: https://www.tinkercad.com/things/0NS8Oft9Xpn-three-balls-cup/ Video of the demonstration: https://youtu.be/NV4646JCJH0 Print in vase mode with enough solid base layers to produce the hold in the bottom of the cup. For my print settings, there were six base layers. The 3.5 radii cup can be printed with the same settings. Some protrusions from the cup give it added strength.