What kind of simple machine is the "domino effect" or dominoes falling against each other?

Question

What kind of simple machine is the "domino effect" or dominoes falling against each other?

Answer 1

I'd say lever.

"A straight rod or board that pivots on a point known as a fulcrum. The fulcrum can be moved depending on the weight of the object to be lifted or the force you wish to exert. Pushing down on one end of a lever results in the upward motion of the opposite end of the fulcrum."