Domino Chain Reaction

LEGO Domino Chain Reaction

If you are studying force and motion, a domino chain reaction is a great activity to demonstrate potential and kinetic energy. First, build a small and very large domino out of LEGO® bricks or other building blocks. You may want to do this ahead of time. Then ask your students if they think the small domino can knock down the large one. If you try it, the small one will just lean against the larger domino. It doesn’t have enough kinetic energy to knock over the larger domino. What about the reverse? Will the large domino knock down the small one? Why?

It only takes a small amount of force to topple a domino because it is not that stable in nature. Dominoes are tall and thin; if they had a deep base (such as a cube) they would be very stable and much more difficult to knock over. However, if you create a domino chain reaction, each domino is only knocking down a new domino that is slightly larger than the previous one (it can be about 1.5x the size for it to work, though if there is slippage it might be better to err on a slightly smaller scale). Have your students create a series of dominoes to make a chain reaction that works. This will take some planning, building, and then they will probably need to tweak or modify the dominoes. Maybe they will need to add another domino between two others if it isn’t able to knock down the next largest one. What is the largest domino they can create?

If you started with a small domino (say 1” by 2”) and doubled the size each time, how many dominoes would you need to topple a standard door? What about a tall and thin building (say 10 stories)? With some simple calculations, you will find that it is a lot fewer dominoes than you might initially guess!

If you have DUPLO blocks handy it will take significantly less time to construct the dominoes, particularly the largest ones. Of course, you can always build a domino chain reaction where the dominoes are of equal size, but doing it this way is always a huge hit!