The speed of the falling depends on the height of the dominoes, the distance between them and the gravity. Experiments show that the falling of the domino row is the fastest, if the distance between dominoes are two third of their height.
The falling row of dominoes can be impressive and successful in the Chain Reaction. Here are some examples:
Set up stable objects, which can fall easily (e.g. matches), parallel, at the same distance. If you push the first object, the shock wave goes through the whole system and all of them will fall. Well, but what is happening? Due to the shock wave, objects are displaced from their equilibrium position and they fall due to gravity.
Put bigger and bigger objects in a row, and see that an object can overturn another object, which is one and a half bigger than the previous one. This can be really impressive in a Chain Reaction! Now, you just only have to figure out the next element of the Chain Reaction, which will be launched by the domino row…