The mechanical resonance

  • Materials:

    Four identical balls, a strong thread, frame or two tripods.

    Procedure.

    In the opposite corners of frame we place the thread.  Symmetrically we fix four pendulums with placticine balls, two of them have the same length equal “h”, third one “1/2h”, and last one “2h”.                              

    We stick out one of the pendulums of length “h”, and I let it down. Then we observe what happens.

    Results.

    When one of the pendulums of length “h” oscillates, its amplitude regularly goes down, and the energy is transported to other, the same pendulum, through the thread. The amplitude oscillations of the second pendulum of length “h” regularly increases.  We observe the mechanical resonance.

    The other pendulums have different lengths, they have different periods and frequency of oscillation so they won’t be stimulated to oscillate. The following equation shows that the period of oscillation of the pendulum does not depend of its amplitude, but only of its length and value of the gravitational acceleration.