Newton’s cradles consist of a series of suspended spherical masses, and are normally started by pulling one ball back. The outer balls then click back and forth for an interesting distraction. 

To make things even more interesting, “TecnoProfesor” made his own version using ping pong balls and RGB LEDs. As the outer balls sway, they light up in sequence, while the three inner balls stay largely in one place.

Power here isn’t provided by kinetic energy, but everything moves via a pair of servo motors. An Arduino Mega is used to control the light/motion simulator, and a button and potentiometer allow the user to change between two modes and variable swing frequency.