Newtons Cradle: Newtoncradle demonstrates the third law of motion with swinging spheres; when oneball is lifted and released it sends force through the rest, pushing the endball in the opposite direction; these swinging kinetic balls are perfectaddition to your office desk decoration accessories or teaching tool at schools Specifications: Size: 5.7x5.7x4.7 in Material: Solid wood+ Fishing line+ Stainless steel balls &structure Occasions: Science Education supplies, Psychotherapy, Stress release,Leisure and entertainment, Birthday present, Holiday gifts, Business gifts Warm Prompt: 1.When you use thisnewtons cradle, please move it in a horizontal line, so the lines will not betangled. 2.The ball in order from the outside to the inside, one by one from the inside of the foam to remove one by one, take special care not to tangle the line together! 3.If it was tangled,you could untangle it still with some patience and time, then you will fix it.Its also a challenge for you, why not have a try? How to untangle it:Firstly, please figure out how the wires were tangled, then follow the wires tountangle it, and you can untangle it in few mins.