As the pendulum swings back and forth, its energy changes from potential energy (the energy it has at the top of its swing, when it is raised up) into kinetic energy (the energy of motion). But the pendulum can be used as a device to explore other concepts as well. The time for one swing doesn't depend on the size of the swing or the mass at the end of the pendulum, only on the length. This is why the pendulum came to be used in the earliest accurate clocks! This classic wooden model offers children a basic concept of the laws of physics. Desktop sized. Recommended age 9+ years