#physical_pendulum__compound_pendulum  pendulum consisting of an actual object allowed to rotate freely around a horizontal axis
  supertype:  pendulum  an apparatus consisting of an object mounted so that it swings freely under the influence of gravity
  subtype:  ballistic_pendulum__ballisticpendulum  a physical pendulum consisting of a large mass suspended from a rod; its displacement is used to measure the velocity of a projectile
  subtype:  clock_pendulum__clockpendulum  a physical pendulum used to regulate a clockwork mechanism

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