I always found Newton’s cradle to be a fun contraption. You know the one: The metal balls that swing in opposite directions, going back and forth as they hit the stationary balls in the middle.
This little desk toy demonstrates powerful principles of momentum and energy. But here’s the thing: To make it work for long periods of time, you need the right materials. The balls need to be highly elastic, so they conserve more energy. And the density of the balls needs to be the same. Let me put it this way: The specifications matter.
