Further informationson the exhibit "Resonance Pendulum"
If you pull the thread for the first time, it can pull the ball a barely perceptible bit on itself with a force smaller than the holding force of the magnet. If you then hold the thread loosely, the barrel swings back to its resting position, then beyond it and then towards you again. If you then pull the thread carefully for the second time, the barrel moves a little further towards you. Thus small portions of energy can gradually be transferred to the pendulum so that it swings out far at the end. However, the rhythm must also be correct, because the energy supply must happen in the oscillation frequency (natural frequency) of the pendulum. By using two or more magnets, several visitors can simultaneously transmit small portions of energy, which leads to a faster build-up.
In general, it can be said that whenever small portions of energy are supplied to a vibrating system in the rhythm of its natural frequency, it can be forced to vibrate with ever larger vibration amplitudes. This phenomenon is called resonance.