# How to Make Pendulum Wave Toy

pendulum is a hanging weight that swings back and forth, like the swinging arm on a grandfather clock or a swing on a playground. When you pull a swing – or any pendulum – up to one side, gravity tugs it back down. But since the swing is attached by a rope or chain, it doesn’t just drop to the ground. Instead, it swings back and forth, over and over. But what happens when you have a bunch of different-sized pendulums swinging together? Make this mesmerizing pendulum wave toy to find out!

Ingredients:

## STEP 13

As the pendulums swing back and forth, they make amazing patterns. That’s because each pendulum has a slightly different period, which is the time it takes to complete a full swing. Think of the “tick-tock” of a grandfather clock. That’s a period!

A pendulum’s period is set by how long its string is. A long pendulum has a long period, meaning it takes a long time to swing back and forth. A shorter pendulum has a shorter period, so it swings faster.

Because the strings go from long to short on the pendulum toy, so do the periods of the pendulums. That means each pendulum swings a little bit faster than the one before it. So because you release them at the same time and height, their different speeds make them go in and out of sync. They swing together, then move in waves, and sometimes look completely chaotic!

### Ali Kaya

This is Ali. Bespectacled and mustachioed father, math blogger, and soccer player. I also do consult for global math and science startups.

2 hours