A simple and sensibly priced version of the old favourite where, once set in motion, the metal balls demonstrate the 'action-and-reaction' phenomenon as they attempt perpetual motion.
A fantastic toy for those children who like repeating motion.
Also a fantastic distraction toy
When one of the steel balls is lifted and allowed to fall back at one end, one will swing out the same distance at the other end
This causes the beginning of 'perpetual motion' which dies down only as a result of friction, gravity and other external forces
An interesting process to watch