Pendulum water painting

I was trying to think of new ways to play with water painting on our little patio and decided it might be fun to experiment with a pendulum. It turned out I was right, but it took several hours before my 3 year old was genuinely interested in it!

I took a plastic pot and made 4 holes in it, one in the centre of the base (pin-sized) and three slightly larger ones just below the top, spaced approximately equally around the rim. Through the three holes I threaded some garden twine/string and held it so that it balanced then tied the three strings together. One was much longer than the others and I tied this around the handle of a brush. I then tied the brush between the backs of two outdoor chairs so the pendulum hung between them. There are no doubt more elegant arrangements that would work too!

Pendulum 'painting' a spiral

To make the pendulum 'paint' a pattern with water, you fill it up with your finger over the hole then let it go. We made spirals, lines and circles with different motions, painting patterns of dots on the ground. As it was a hot day, they dried in about 10 minutes, giving us a blank canvas to start again. There was no mess, aside from the boys getting a little wet (which soon dried) and the little one in particular enjoyed swinging it and letting the water splash his toes.

It proved interesting to both boys

After a while, my older one became interested in the different patterns and he watched carefully as we made a circle where the dots got closer to the centre so it eventually filled in the full circle before the pendulum stopped. We talked about how it was going anticlockwise, and my son set the next one going clockwise. We also talked about how gravity pulls it towards the middle of the circle i.e. when the pendulum hangs straight downwards. He also made some different spiral patterns, declaring that he loved the patterns the pendulum made (and he liked the word pendulum too!). He also reminded me that the drawings disappeared because the water evaporated, just like our other water painting and the water in his water cycle bottle

There's lots of fun physics we can explore when the boys are older with pendulums, but for now this activity was just about introducing the idea of a pendulum and watching it create patterns in front of their eyes. It only took about 5 minutes to set up and it'll be even quicker next time as I will just need to put out the chairs and brush rather than making holes and threading string!