This K constant spring apparatus is totally made of iron with powder coating. one end of a long flat spiral spring is fixed and the lower end is pulled by a short jerk and released, longitudinal waves are produced. The apparatus consists of a spiral spring about 25mm diameter and 10cm length. The upper end of the spring is suspended from a chuck nut and the lower end is provided with a small pointer which moves over a vertical wooden meter scale. the lower end is also provided with hook for carrying weights. All this setup is provided on a heavy metal base, supplied with weights.