Thus, we may assume that when a body
handled on a vibrating surface is forced to move at a
frequency (ω) lower than its natural frequency (ω0), it will
move in a direction opposite to that of a body forced to
move at a frequency higher than its natural frequency.
Experiments with two bodies (1 and 2, respectively) having
different resonant angular frequency (ω01 < ω > ω02), have
shown that when the two bodies are placed on a vibrating
surface with a frequency of ω, they moved in opposite
directions to each other