Fletcher Trolley :All metal, capable of being assembled and dismantled easily. A large metal trolley with removable cylindrical weights is fitted with wheels which run with very little Friction on a track of two steel, rods 150 cm long. The rail rods are held in heavy clamps which are fitted in two vertical rods, mounted on cast iron feet. The steel vibrator is fitted to one of the vertical rods and frictionless pulley to the other. The unit is capable to verify the law under different conditions, Complete with cord, scale pan, brush and ink.