Four pendulums on rod: Same length, different masses.

Four Pendulums: Same Lengths, different Masses. 4 pendula of equal lengths (approximately 50 cm) are suspended from a rod. The balls are made of different materials -- wood, steel, brass and lead -- and their masses are 37g, 130g, 230g and 320g respectively. Due to the mass independence of the period, the pendula should all swing in unison.