Technique 27: Seesaw
  Technik XY

You build a kind of seesaw with a water bottle (and a needle in it) on the one side. The needle is connected with a lego car. On the other side of the seesaw, there is one domino and some weights. When the car begins driving, the needle is pulled out of the bottle and the water flows out - as long as the balance changes and dominos topple on the other side.