Dominoes are are actually quite powerful. Discussed on this website: http://www.insidescience.org/content/dominoes-more-powerful-you-think/924. Dominoes, once pushed, can knock over a domino 1.5 the size of the previous one. If you set up 29 dominoes- the first one being the size of a normal domino then the others following the first one gets increased in size by 1.5x the size of the previous, the last domino would be the size of the empire state building. Only a small amount of the mechanical energy is lost when friction between the falling dominoes creates heat. So most of the energy is transferred to the next making them tip over keeping most of the mechanical energy in the system.