Pendulums on Stand

Show the difference between three pendulums with different lengths.

Heavy metal stand with a meter scale mounted on a vertical rod can hold three pendulums of 5cm apart with points for suspension of cords.
Three 2.5cm pendulum bobs of wood, iron, and steel are suspended from a common hanger mounted on a vertical rod screwed to a heavy metal stand. A meter scale and a sliding index with projecting piece is provided. The sliding index can control the length of the first cord. Zero of meter stick is placed at the bottom and when the center of the pendulum is placed opposite this point, the length of the pendulum is read directly from the position of the slider.