Normal mode

Okay, kiddo, so imagine you're riding on a swing set. When you start off, the swing is still and doesn't make any noise. But when you begin to swing back and forth, you start to hear a sound that goes “whoosh-whoosh-whoosh.”

This is because you've entered what we call a "normal mode." It just means that you've started moving in a particular way that causes the swing to vibrate at a specific frequency.

Basically, a normal mode is a way things move or vibrate that is very predictable and has a specific pattern. Sometimes things can have more than one normal mode, like a guitar string that can make different musical notes depending on how you pluck it.

So, next time you’re on a swing, listen for the whooshing sound – you might just be entering a normal mode!