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Pendulums dancing in harmony

In Short

Several pendulums ending in different coloured lights swing in a choreography of changing constellations. Watch the beautiful play of them moving first simultaneously, then like two snakes, then alternating… In doing so you will learn that, contrary to our intuition, the speed of a pendulum does not depend on its mass but only on its length.

Details and Theory

The pendulum is a fundamental system in physics, its so-called harmonic oscillations find relevance in many different fields such as quantum physics, electronics and acoustics. For the wave pendulum effect, the frequencies of the pendulums must be integer multiples of each other. In this regard, the wave pendulum is very similar to an instrument. The frequencies of the pendulums are tuned only by changing their length.

By seeing that the frequency or speed does only depend on the length and not on the body – its mass or form – that oscillates, one learns a fundamental law of physics, known since Galileo Galilei. This is because the earth’s gravitational pull affects all bodies equally, no matter how heavy they are. It goes against our intuition: does not a feather fall to the ground much more slowly than a ball, for example? But we are being deceived by something else: the feather falls more slowly because it can be swirled more easily by the air. In a vacuum, stone and feather fall to the ground at the same speed.